json_streaming/blocking/

read.rs

use crate::blocking::io::BlockingRead;
use core::str::FromStr;
use crate::shared::*;

/// A [JsonReader] wraps a sequence of bytes, aggregating them into a sequence of JSON tokens. It
///  is in essentially a tokenizer, adding some rudimentary convenience for JSON's grammar.
///
/// It does *not* try to be a full-blown JSON parser. The reason is that if an application consumes
///  an actual JSON document, it assumes structure beyond the document being a valid JSON document
///  ('name is a mandatory string, age is a u32, but it is ok if it is null or not present in the
///  first place'). [JsonReader] makes it easy for application code to consume data based on such
///  assumptions - and while it does, application code checks the document's conformity to the JSON
///  grammar automatically.
///
/// A [JsonReader] wraps and consumes a [BlockingRead] which is basically a same abstraction as a
///  [std::io::Read] but without enforcing the dependency on `std`. For the majority of users who
///  don't care about that, there is a blanket implementation of [BlockingRead] for [std::io::Read],
///  letting you ignore distinction between the two.
///
/// The [JsonReader] holds a mutable reference to the reader rather than taking ownership of it.
///  That means it needs to have a lifetime parameter, allowing the compiler to ensure that the
///  reader lives at least as long as the wrapping [JsonReader].
///
/// The [JsonReader] also holds a fixed read buffer which it uses to assemble tokens. [JsonReader]
///  can either work with a buffer passed to it on construction, or it can allocate the buffer as a
///  convenience, and it does not do *any* memory allocation on the heap beyond that.
///
/// The buffer is fixed in length, and if some token (e.g. a string value) does not fit into the
///  buffer, that causes a failure. While this may look like an inconvenient restriction, it is
///  actually an important security safeguard: JSON documents often come from external sources and
///  have limited trustworthiness at best. Without an upper bound on token size, a maliciously or
///  negligently created document could contain a string literal with a size of a gigabyte,
///  working as a denial-of-service attack. JSON parsers that work on materialized documents often
///  address this by placing a restriction on the maximum size of the whole document.
///
/// The following code snippet shows a small working example of reading a JSON document with a
///  single object:
///
/// ```
/// use json_streaming::blocking::*;
/// use json_streaming::shared::*;
///
/// fn read_something(r: &mut impl std::io::Read) -> JsonParseResult<(), std::io::Error> {
///     let mut json_reader = JsonReader::new(1024, r);
///
///     json_reader.expect_start_object()?;
///     loop {
///         match json_reader.expect_key()? {
///             Some("a") => println!("a: {}", json_reader.expect_string()?),
///             Some("b") => println!("b: {}", json_reader.expect_string()?),
///             Some(_other) => {
///                 return Err(JsonParseError::Parse("unexpected key parsing 'person'", json_reader.location()));
///             },
///             None => break,
///         }
///     }
///     Ok(())
/// }
/// ```
pub struct JsonReader<'a, B: AsMut<[u8]>, R: BlockingRead> {
    inner: ReaderInner<B, R::Error>,
    reader: &'a mut R,
}

#[cfg(feature = "std")]
impl<'a, R: BlockingRead> JsonReader<'a, Vec<u8>, R> {
    /// Create a [JsonReader], allocating a read buffer of given size on the heap.
    pub fn new(buf_size: usize, reader: &'a mut R) -> Self {
        let buf = vec![0u8; buf_size];
        Self::new_with_provided_buffer(buf, reader, false)
    }

    /// Create a [JsonReader] without requiring commas between objects. This is intended for
    ///  reading [https://jsonlines.org] documents - see the `jsonlines.rs` example for details.
    pub fn new_with_lenient_comma_handling(buf_size: usize, reader: &'a mut R) -> Self {
        let buf = vec![0u8; buf_size];
        Self::new_with_provided_buffer(buf, reader, true)
    }
}

impl<'a, B: AsMut<[u8]>, R: BlockingRead> JsonReader<'a, B, R> {
    /// Create a [JsonReader] that uses an externally provided buffer as its read buffer. The main
    ///  reason to do this is to avoid heap allocation in a no-std environment.
    pub fn new_with_provided_buffer(buf: B, reader: &'a mut R, lenient_comma_handling: bool) -> Self {
        Self {
            inner: ReaderInner::new(buf, lenient_comma_handling),
            reader,
        }
    }

    /// Return the next JSON token. This is the work horse of [JsonReader] and the foundation for
    ///  other convenience abstraction.
    ///
    /// The function does only limited checks of JSON grammar and basically returns whatever tokens
    ///  it finds.
    pub fn next(&mut self) -> JsonParseResult<JsonReadToken<'_>, R::Error> {
        self.consume_whitespace()?;

        match self.read_next_byte()? {
            None => {
                Ok(JsonReadToken::EndOfStream)
            },
            Some(b',') => {
                self.inner.on_comma()?;
                self.next()
            }
            Some(b'{') => {
                self.inner.ensure_accept_value()?;
                self.inner.state = ReaderState::Initial;
                Ok(JsonReadToken::StartObject)
            },
            Some(b'}') => {
                self.inner.ensure_accept_end_nested()?;
                self.inner.state = ReaderState::AfterValue;
                Ok(JsonReadToken::EndObject)
            },
            Some(b'[') => {
                self.inner.ensure_accept_value()?;
                self.inner.state = ReaderState::Initial;
                Ok(JsonReadToken::StartArray)
            },
            Some(b']') => {
                self.inner.ensure_accept_end_nested()?;
                self.inner.state = ReaderState::AfterValue;
                Ok(JsonReadToken::EndArray)
            },

            Some(b'n') => {
                self.inner.state_change_for_value()?;
                self.consume_null_literal()
            },
            Some(b't') => {
                self.inner.state_change_for_value()?;
                self.consume_true_literal()
            },
            Some(b'f') => {
                self.inner.state_change_for_value()?;
                self.consume_false_literal()
            },

            Some(b'"') => self.parse_after_quote(), // key or string value based on following ':'
            Some(b) => {
                self.inner.state_change_for_value()?;
                match b {
                    b'-' | b'0'..=b'9' => self.parse_number_literal(b),
                    _ => self.parse_err("invalid JSON literal")
                }
            },
        }
    }

    /// This is the function for the loop to read the members of a JSON object: It returns either
    ///  a JSON key or `None` if it encounters the `}` that ends the object. All other tokens are
    ///  invalid and cause the function to fail.
    pub fn expect_key(&mut self) -> JsonParseResult<Option<&str>, R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::Key(key) => Ok(Some(key)),
            JsonReadToken::EndObject => Ok(None),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// Returns a JSON number as a [JsonNumber], and fails if the next token is anything other
    ///  than a number. That includes the case that the next token is `null` - if the number
    ///  is optional and `null` a valid value, use [JsonReader::expect_opt_raw_number] instead.
    pub fn expect_raw_number(&mut self) -> JsonParseResult<JsonNumber<'_>, R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::NumberLiteral(n) => Ok(n),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// Same as [JsonReader::expect_raw_number], except that it returns `Ok(None)` if it reaches the end of an
    ///  array instead
    pub fn expect_raw_number_or_end_array(&mut self) -> JsonParseResult<Option<JsonNumber<'_>>, R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::NumberLiteral(n) => Ok(Some(n)),
            JsonReadToken::EndArray => Ok(None),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// Returns a [JsonNumber] if the next token is a JSON number, or `None` if the next token
    ///  is `null`. All other tokens cause the function to fail.
    pub fn expect_opt_raw_number(&mut self) -> JsonParseResult<Option<JsonNumber<'_>>, R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::NullLiteral => Ok(None),
            JsonReadToken::NumberLiteral(n) => Ok(Some(n)),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// Same as [JsonReader::expect_opt_raw_number], except that it returns `Ok(None)` if it reaches the end of an
    ///  array instead
    pub fn expect_opt_raw_number_or_end_array(&mut self) -> JsonParseResult<Option<Option<JsonNumber<'_>>>, R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::NullLiteral => Ok(Some(None)),
            JsonReadToken::NumberLiteral(n) => Ok(Some(Some(n))),
            JsonReadToken::EndArray => Ok(None),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// Returns a number parsed to an application-provided type, failing if the next token is not
    ///  a JSON number or the number is not parseable to the provided type (e.g. trying to
    ///  get retrieve a floating point number as a u32).
    ///
    /// The expected numeric type can be provided explicitly, like this:
    /// ```
    /// # use json_streaming::blocking::*;
    /// # use json_streaming::shared::*;
    /// # fn get_num() -> JsonParseResult<(), std::io::Error> {
    /// # let buf = "123";
    /// # let mut r = std::io::Cursor::new(buf);
    /// # let mut json_reader = JsonReader::new(128, &mut r);
    /// let n = json_reader.expect_number::<u32>()?;
    /// # Ok(()) }
    /// ```
    /// or inferred by the compiler:
    /// ```
    /// # use json_streaming::blocking::*;
    /// # use json_streaming::shared::*;
    /// # fn get_num() -> JsonParseResult<(), std::io::Error> {
    /// # let buf = "123";
    /// # let mut r = std::io::Cursor::new(buf);
    /// # let mut json_reader = JsonReader::new(128, &mut r);
    /// let n:u32 = json_reader.expect_number()?;
    /// # Ok(()) }
    /// ```
    pub fn expect_number<T: FromStr>(&mut self) -> JsonParseResult<T, R::Error> {
        let n = self.expect_raw_number()?;
        match n.parse::<T>() {
            Ok(n) => Ok(n),
            Err(_) => self.parse_err("invalid number"),
        }
    }

    /// Same as [JsonReader::expect_number], except that it returns `Ok(None)` if it reaches the end of an
    ///  array instead
    pub fn expect_number_or_end_array<T: FromStr>(&mut self) -> JsonParseResult<Option<T>, R::Error> {
        match self.expect_raw_number_or_end_array()? {
            None => Ok(None),
            Some(n) => {
                match n.parse::<T>() {
                    Ok(n) => Ok(Some(n)),
                    Err(_) => self.parse_err("invalid number"),
                }
            }
        }
    }

    /// The same as [JsonReader::expect_number], but accepting a `null` literal which it
    ///  returns as `None`.
    pub fn expect_opt_number<T: FromStr>(&mut self) -> JsonParseResult<Option<T>, R::Error> {
        match self.expect_opt_raw_number()? {
            Some(n) => {
                match n.parse::<T>() {
                    Ok(n) => Ok(Some(n)),
                    Err(_) => self.parse_err("invalid number"),
                }
            }
            None => Ok(None),
        }
    }

    /// Same as [JsonReader::expect_opt_number], except that it returns `Ok(None)` if it reaches the end of an
    ///  array instead
    pub fn expect_opt_number_or_end_array<T: FromStr>(&mut self) -> JsonParseResult<Option<Option<T>>, R::Error> {
        match self.expect_opt_raw_number_or_end_array()? {
            Some(Some(n)) => {
                match n.parse::<T>() {
                    Ok(n) => Ok(Some(Some(n))),
                    Err(_) => self.parse_err("invalid number"),
                }
            }
            Some(None) => Ok(Some(None)),
            None => Ok(None),
        }
    }

    /// If the next token is a string literal, return that, and fail for any other token.
    pub fn expect_string(&mut self) -> JsonParseResult<&str, R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::StringLiteral(s) => Ok(s),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// Same as [JsonReader::expect_string], except that it returns `Ok(None)` if it reaches the end of an
    ///  array instead
    pub fn expect_string_or_end_array(&mut self) -> JsonParseResult<Option<&str>, R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::StringLiteral(s) => Ok(Some(s)),
            JsonReadToken::EndArray => Ok(None),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// The same as [JsonReader::expect_string], but accepting a `null` literal which is
    ///  returned as `None`.
    pub fn expect_opt_string(&mut self) -> JsonParseResult<Option<&str>, R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::NullLiteral => Ok(None),
            JsonReadToken::StringLiteral(s) => Ok(Some(s)),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// Same as [JsonReader::expect_opt_string], except that it returns `Ok(None)` if it reaches the end of an
    ///  array instead
    pub fn expect_opt_string_or_end_array(&mut self) -> JsonParseResult<Option<Option<&str>>, R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::NullLiteral => Ok(Some(None)),
            JsonReadToken::StringLiteral(s) => Ok(Some(Some(s))),
            JsonReadToken::EndArray => Ok(None),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// `true` and `false` literals are returned as a boolean token, all other tokens cause the
    ///  function to fail.
    pub fn expect_bool(&mut self) -> JsonParseResult<bool, R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::BooleanLiteral(b) => Ok(b),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// Same as [JsonReader::expect_bool], except that it returns `Ok(None)` if it reaches the end of an
    ///  array instead
    pub fn expect_bool_or_end_array(&mut self) -> JsonParseResult<Option<bool>, R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::BooleanLiteral(b) => Ok(Some(b)),
            JsonReadToken::EndArray => Ok(None),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// The same as [JsonReader::expect_bool], but accepting a `null` literal which is
    ///  returned as `None`.
    pub fn expect_opt_bool(&mut self) -> JsonParseResult<Option<bool>, R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::NullLiteral => Ok(None),
            JsonReadToken::BooleanLiteral(b) => Ok(Some(b)),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// Same as [JsonReader::expect_opt_bool], except that it returns `Ok(None)` if it reaches the end of an
    ///  array instead
    pub fn expect_opt_bool_or_end_array(&mut self) -> JsonParseResult<Option<Option<bool>>, R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::NullLiteral => Ok(Some(None)),
            JsonReadToken::BooleanLiteral(b) => Ok(Some(Some(b))),
            JsonReadToken::EndArray => Ok(None),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// Fails for any token except the `{` that starts an object.
    pub fn expect_start_object(&mut self) -> JsonParseResult<(), R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::StartObject => Ok(()),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// Same as [JsonReader::start_object], except that it returns `Ok(None)` if it reaches the end of an
    ///  array instead
    pub fn expect_start_object_or_end_array(&mut self) -> JsonParseResult<Option<()>, R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::StartObject => Ok(Some(())),
            JsonReadToken::EndArray => Ok(None),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// The same as [JsonReader::expect_start_object], but accepting a `null` literal which is
    ///  returned as `None`.
    pub fn expect_opt_start_object(&mut self) -> JsonParseResult<Option<()>, R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::NullLiteral => Ok(None),
            JsonReadToken::StartObject => Ok(Some(())),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// Same as [JsonReader::expect_opt_start_object], except that it returns `Ok(None)` if it reaches the end of an
    ///  array instead
    pub fn expect_opt_start_object_or_end_array(&mut self) -> JsonParseResult<Option<Option<()>>, R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::NullLiteral => Ok(Some(None)),
            JsonReadToken::StartObject => Ok(Some(Some(()))),
            JsonReadToken::EndArray => Ok(None),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// Fails for any token except the `}` that ends an object.
    pub fn expect_end_object(&mut self) -> JsonParseResult<(), R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::EndObject => Ok(()),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// Fails for any token except the `[` that starts an array.
    pub fn expect_start_array(&mut self) -> JsonParseResult<(), R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::StartArray => Ok(()),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// Same as [JsonReader::expect_start_array], except that it returns `Ok(None)` if it reaches the end of an
    ///  array instead
    pub fn expect_start_array_or_end_array(&mut self) -> JsonParseResult<Option<()>, R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::StartArray => Ok(Some(())),
            JsonReadToken::EndArray => Ok(None),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// The same as [JsonReader::expect_start_array], but accepting a `null` literal which is
    ///  returned as `None`.
    pub fn expect_opt_start_array(&mut self) -> JsonParseResult<Option<()>, R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::NullLiteral => Ok(None),
            JsonReadToken::StartArray => Ok(Some(())),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// Same as [JsonReader::opt_start_array], except that it returns `Ok(None)` if it reaches the end of an
    ///  array instead
    pub fn expect_opt_start_array_or_end_array(&mut self) -> JsonParseResult<Option<Option<()>>, R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::NullLiteral => Ok(Some(None)),
            JsonReadToken::StartArray => Ok(Some(Some(()))),
            JsonReadToken::EndArray => Ok(None),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// Fails for any token except the `]` that ends an array.
    pub fn expect_end_array(&mut self) -> JsonParseResult<(), R::Error> {
        let location = self.location();
        let next = self.next()?;
        match next {
            JsonReadToken::EndArray => Ok(()),
            other => Err(JsonParseError::Parse(other.kind(), location)),
        }
    }

    /// This function assumes that it is called inside an object or array, and silently consumes
    ///  all tokens until and including the closing `}` or `]`.
    ///
    /// This function is useful for gracefully ignoring array elements with an unsupported type. See
    ///  the `skipping.rs` example for details.
    pub fn skip_to_end_of_current_scope(&mut self) -> JsonParseResult<(), R::Error> {
        let mut nesting_level = 1;
        loop {
            match self.next()? {
                JsonReadToken::StartObject | JsonReadToken::StartArray => {
                    nesting_level += 1;
                }
                JsonReadToken::EndObject | JsonReadToken::EndArray=> {
                    nesting_level -= 1;
                    if nesting_level == 0 {
                        break;
                    }
                }
                JsonReadToken::EndOfStream => {
                    return Err(JsonParseError::Parse(JsonReadToken::EndOfStream.kind(), self.location()));
                }
                _ => {
                    continue;
                }
            }
        }
        Ok(())
    }

    /// This function skips the value starting with the next token. This can be a single-token value,
    ///  but it can also be an object or array of unknown structure and nesting depth, in which
    ///  case this function silently consumes tokens until it reaches the matching closing `}` or
    ///  `]`.
    ///
    /// This function is useful for gracefully ignoring object members with an unknown key - see
    ///  the `skipping.rs` example for details.
    pub fn skip_value(&mut self) -> JsonParseResult<(), R::Error> {
        match self.next()? {
            JsonReadToken::Key(_) |
            JsonReadToken::EndObject |
            JsonReadToken::EndArray |
            JsonReadToken::EndOfStream => {
                Err(JsonParseError::Parse(JsonReadToken::EndOfStream.kind(), self.location()))
            }
            JsonReadToken::StartObject |
            JsonReadToken::StartArray => {
                self.skip_to_end_of_current_scope()
            }
            JsonReadToken::StringLiteral(_) |
            JsonReadToken::NumberLiteral(_) |
            JsonReadToken::BooleanLiteral(_) |
            JsonReadToken::NullLiteral => {
                Ok(())
            }
        }
    }

    fn consume_whitespace(&mut self) -> JsonParseResult<(), R::Error> {
        while let Some(next) = self.read_next_byte()? {
            match next {
                b' ' | b'\t' | b'\n' | b'\r' => {
                }
                next => {
                    self.inner.parked_next = Some(next);
                    break;
                }
            }
        }
        Ok(())
    }

    fn read_next_byte(&mut self) -> JsonParseResult<Option<u8>, R::Error> {
        // Parsing JSON requires a lookahead of a single byte, which is stored in 'parked_next'
        if let Some(parked) = self.inner.parked_next.take() {
            return Ok(Some(parked));
        }

        if let Some(byte) =self.reader.read()? {
            self.inner.cur_location.after_byte(byte);
            Ok(Some(byte))
        }
        else {
            Ok(None)
        }
    }

    fn consume_null_literal(&mut self) -> JsonParseResult<JsonReadToken<'_>, R::Error> {
        if self.read_next_byte()? != Some(b'u') {
            return self.parse_err("incomplete null literal");
        }
        if self.read_next_byte()? != Some(b'l') {
            return self.parse_err("incomplete null literal");
        }
        if self.read_next_byte()? != Some(b'l') {
            return self.parse_err("incomplete null literal");
        }
        Ok(JsonReadToken::NullLiteral)
    }

    fn consume_true_literal(&mut self) -> JsonParseResult<JsonReadToken<'_>, R::Error> {
        if self.read_next_byte()? != Some(b'r') {
            return self.parse_err("incomplete true literal");
        }
        if self.read_next_byte()? != Some(b'u') {
            return self.parse_err("incomplete true literal");
        }
        if self.read_next_byte()? != Some(b'e') {
            return self.parse_err("incomplete true literal");
        }
        Ok(JsonReadToken::BooleanLiteral(true))
    }

    fn consume_false_literal(&mut self) -> JsonParseResult<JsonReadToken<'_>, R::Error> {
        if self.read_next_byte()? != Some(b'a') {
            return self.parse_err("incomplete false literal");
        }
        if self.read_next_byte()? != Some(b'l') {
            return self.parse_err("incomplete false literal");
        }
        if self.read_next_byte()? != Some(b's') {
            return self.parse_err("incomplete false literal");
        }
        if self.read_next_byte()? != Some(b'e') {
            return self.parse_err("incomplete false literal");
        }
        Ok(JsonReadToken::BooleanLiteral(false))
    }

    fn parse_after_quote(&mut self) -> JsonParseResult<JsonReadToken<'_>, R::Error> {
        self.inner.ind_end_buf = 0;

        loop {
            if let Some(next) = self.read_next_byte()? {
                match next {
                    b'"' => break,
                    b'\\' => {
                        match self.read_next_byte()? {
                            Some(b'"') => self.inner.append_to_buf(b'"')?,
                            Some(b'\\') => self.inner.append_to_buf(b'\\')?,
                            Some(b'/') => self.inner.append_to_buf(b'/')?,
                            Some(b'b') => self.inner.append_to_buf(0x08)?,
                            Some(b'f') => self.inner.append_to_buf(0x0c)?,
                            Some(b'n') => self.inner.append_to_buf(b'\n')?,
                            Some(b'r') => self.inner.append_to_buf(b'\r')?,
                            Some(b't') => self.inner.append_to_buf(b'\t')?,
                            Some(b'u') => {
                                let cp = self.parse_unicode_codepoint()?;
                                self.inner.append_code_point(cp)?;
                            },
                            _ => return self.parse_err("invalid escape in string literal"),
                        }
                    },
                    ch => {
                        self.inner.append_to_buf(ch)?;
                    }
                }
            }
            else {
                return self.parse_err("unterminated string literal");
            }
        }

        // the buffer contains the string's contents - the next character determines whether this
        //  is key or a string value. Recall that we don't check for valid JSON.

        self.consume_whitespace()?;
        match self.read_next_byte()? {
            Some(b':') => {
                match self.inner.state {
                    ReaderState::Initial |
                    ReaderState::BeforeEntry => {
                        self.inner.state = ReaderState::AfterKey;
                    }
                    ReaderState::AfterKey => {
                        return self.parse_err("two keys without value");
                    }
                    ReaderState::AfterValue => {
                        return self.parse_err("missing comma");
                    }
                }
                Ok(JsonReadToken::Key(self.inner.buf_as_str()?))
            },
            other => {
                self.inner.state_change_for_value()?;
                self.inner.parked_next = other;
                Ok(JsonReadToken::StringLiteral(self.inner.buf_as_str()?))
            }
        }
    }

    fn parse_unicode_codepoint(&mut self) -> JsonParseResult<u16, R::Error> {
        // exactly four hex digits specifying a code point
        let mut cp: u16 = 0;
        for _ in 0..4 {
            if let Some(b) = self.read_next_byte()? {
                cp = cp << 4;
                match b {
                    b'0'..=b'9' => cp += (b - b'0') as u16,
                    b'a'..=b'f' => cp += (b - b'a' + 10) as u16,
                    b'A'..=b'Z' => cp += (b - b'A' + 10) as u16,
                    _ => {
                        return self.parse_err("not a four-digit hex number after \\u");
                    }
                }
            }
            else {
                return self.parse_err("incomplete UTF codepoint in string literal");
            }
        }
        Ok(cp)
    }

    fn parse_number_literal(&mut self, b: u8) -> JsonParseResult<JsonReadToken<'_>, R::Error> {
        self.inner.buf.as_mut()[0] = b;
        self.inner.ind_end_buf = 1;

        while let Some(next) = self.read_next_byte()? {
            match next {
                b'0'..=b'9' |
                b'+' | b'-' | b'e' | b'E' |
                b'.' => {
                    self.inner.append_to_buf(next)?;
                }
                other => {
                    self.inner.parked_next = Some(other);
                    break;
                }
            }
        }
        Ok(JsonReadToken::NumberLiteral(JsonNumber(self.inner.buf_as_str().unwrap())))
    }

    /// convenience function for creating a parse error with the current location
    pub fn parse_err<T>(&self, msg: &'static str) -> JsonParseResult<T, R::Error> {
        self.inner.parse_err(msg)
    }

    /// Returns the current parse location in the underlying reader - offset, row and column.
    #[inline]
    pub fn location(&self) -> Location {
        self.inner.cur_location
    }
}

#[cfg(test)]
mod tests {
    use std::io;
    use super::*;
    use rstest::*;
    use std::io::{Cursor, Read};

    fn assert_is_similar_error(actual: &JsonParseError<std::io::Error>, expected: &JsonParseError<std::io::Error>) {
        match actual {
            JsonParseError::Io(self_e) => {
                if let JsonParseError::Io(other_e) = expected {
                    assert_eq!(self_e.kind(), other_e.kind());
                    return;
                }
            }
            JsonParseError::Utf8(_) => {
                if let JsonParseError::Utf8(_) = expected {
                    return;
                }
            }
            JsonParseError::Parse(_, _) => {
                if let JsonParseError::Parse(_, _) = expected {
                    return;
                }
            }
            JsonParseError::BufferOverflow(_) => {
                if let JsonParseError::BufferOverflow(_) = expected {
                    return;
                }
            }
        }

        panic!("{:?} != {:?}", actual, expected);
    }

    #[rstest]
    #[case::empty("", vec![], None)]
    #[case::empty_repeated_end_of_stream("", vec![JsonReadToken::EndOfStream, JsonReadToken::EndOfStream, JsonReadToken::EndOfStream, ], None)]

    #[case::null_literal("null", vec![JsonReadToken::NullLiteral], None)]
    #[case::true_literal("true", vec![JsonReadToken::BooleanLiteral(true)], None)]
    #[case::false_literal("false", vec![JsonReadToken::BooleanLiteral(false)], None)]
    #[case::start_object("{", vec![JsonReadToken::StartObject], None)]
    #[case::end_object("{}", vec![JsonReadToken::StartObject, JsonReadToken::EndObject], None)]
    #[case::start_array("[", vec![JsonReadToken::StartArray], None)]
    #[case::end_array("[]", vec![JsonReadToken::StartArray, JsonReadToken::EndArray], None)]

    #[case::key("\"xyz\":", vec![JsonReadToken::Key("xyz")], None)]
    #[case::key_with_escapes("\"x\\ry\\nz\":", vec![JsonReadToken::Key("x\ry\nz")], None)]
    #[case::key_ws("\"xyz\" \n:", vec![JsonReadToken::Key("xyz")], None)]
    #[case::key_value("\"xyz\" \n:\r\tfalse", vec![JsonReadToken::Key("xyz"), JsonReadToken::BooleanLiteral(false)], None)]

    #[case::string_literal(r#""abc""#, vec![JsonReadToken::StringLiteral("abc")], None)]
    #[case::string_literal_empty(r#""""#, vec![JsonReadToken::StringLiteral("")], None)]
    #[case::string_literal_quot(r#""\"""#, vec![JsonReadToken::StringLiteral("\"")], None)]
    #[case::string_literal_backslash(r#""\\""#, vec![JsonReadToken::StringLiteral("\\")], None)]
    #[case::string_literal_slash(r#""\/""#, vec![JsonReadToken::StringLiteral("/")], None)]
    #[case::string_literal_backslash(r#""\b""#, vec![JsonReadToken::StringLiteral("\x08")], None)]
    #[case::string_literal_formfeed(r#""\f""#, vec![JsonReadToken::StringLiteral("\x0c")], None)]
    #[case::string_literal_linefeed(r#""\n""#, vec![JsonReadToken::StringLiteral("\n")], None)]
    #[case::string_literal_carriage_return(r#""\r""#, vec![JsonReadToken::StringLiteral("\r")], None)]
    #[case::string_literal_tab(r#""\t""#, vec![JsonReadToken::StringLiteral("\t")], None)]
    #[case::string_literal_unicode_y(r#""\u0079""#, vec![JsonReadToken::StringLiteral("y")], None)]
    #[case::string_literal_unicode_umlaut_two_bytes(r#""\u00e4""#, vec![JsonReadToken::StringLiteral("ä")], None)]
    #[case::string_literal_unicode_omega_two_bytes(r#""\u03a9""#, vec![JsonReadToken::StringLiteral("Ω")], None)]
    #[case::string_literal_unicode_euro_three_bytes(r#""\u20ac""#, vec![JsonReadToken::StringLiteral("€")], None)]
    #[case::string_literal_combined(r#""a\n b\t \u00e4öü \u03a9 12.2\u20ac""#, vec![JsonReadToken::StringLiteral("a\n b\t äöü Ω 12.2€")], None)]

    #[case::number_literal("123", vec![JsonReadToken::NumberLiteral(JsonNumber("123"))], None)]
    #[case::number_literal_negative("-456", vec![JsonReadToken::NumberLiteral(JsonNumber("-456"))], None)]
    #[case::number_literal_zero("0", vec![JsonReadToken::NumberLiteral(JsonNumber("0"))], None)]
    #[case::number_literal_fraction("0.92", vec![JsonReadToken::NumberLiteral(JsonNumber("0.92"))], None)]
    #[case::number_literal_fraction_small("0.0000000000000092", vec![JsonReadToken::NumberLiteral(JsonNumber("0.0000000000000092"))], None)]
    #[case::number_literal_fraction_neg("-0.0000000000000092", vec![JsonReadToken::NumberLiteral(JsonNumber("-0.0000000000000092"))], None)]
    #[case::number_literal_exp_lower("0.92e4", vec![JsonReadToken::NumberLiteral(JsonNumber("0.92e4"))], None)]
    #[case::number_literal_exp_upper("0.92E6", vec![JsonReadToken::NumberLiteral(JsonNumber("0.92E6"))], None)]
    #[case::number_literal_pos_exp_lower("0.92e+4", vec![JsonReadToken::NumberLiteral(JsonNumber("0.92e+4"))], None)]
    #[case::number_literal_pos_exp_upper("0.92E+6", vec![JsonReadToken::NumberLiteral(JsonNumber("0.92E+6"))], None)]
    #[case::number_literal_neg_exp_lower("0.92e-4", vec![JsonReadToken::NumberLiteral(JsonNumber("0.92e-4"))], None)]
    #[case::number_literal_neg_exp_upper("0.92E-6", vec![JsonReadToken::NumberLiteral(JsonNumber("0.92E-6"))], None)]

    #[case::number_literal_no_leading_zero(".1", vec![], Some(JsonParseError::Parse("invalid JSON literal", Location::start())))]
    #[case::no_matching_literal("x", vec![], Some(JsonParseError::Parse("invalid JSON literal", Location::start())))]
    #[case::invalid_number_continuation("1x", vec![JsonReadToken::NumberLiteral(JsonNumber("1"))], Some(JsonParseError::Parse("missing comma", Location::start())))]
    #[case::invalid_number_continuation_quote("x\"", vec![], Some(JsonParseError::Parse("invalid JSON literal", Location::start())))]

    #[case::string_literal_unterminated_short(r#""abc "#, vec![], Some(JsonParseError::Parse("unterminated string literal", Location::start())))]
    #[case::string_literal_unterminated_long(r#""abc                                                                         "#, vec![], Some(JsonParseError::BufferOverflow(Location::start())))]
    #[case::string_literal_invalid_escape(r#""\q""#, vec![], Some(JsonParseError::Parse("invalid escape in string literal", Location::start())))]
    #[case::string_literal_unicode_string_ends(r#""\u004""#, vec![], Some(JsonParseError::Parse("not a four-digit hex number after \\u", Location::start())))]
    #[case::string_literal_unicode_invalid_character_1(r#""\ux041""#, vec![], Some(JsonParseError::Parse("not a four-digit hex number after \\u", Location::start())))]
    #[case::string_literal_unicode_invalid_character_2(r#""\u0x41""#, vec![], Some(JsonParseError::Parse("not a four-digit hex number after \\u", Location::start())))]
    #[case::string_literal_unicode_invalid_character_3(r#""\u00x1""#, vec![], Some(JsonParseError::Parse("not a four-digit hex number after \\u", Location::start())))]
    #[case::string_literal_unicode_invalid_character_4(r#""\u004x""#, vec![], Some(JsonParseError::Parse("not a four-digit hex number after \\u", Location::start())))]
    #[case::string_literal_unicode_uppercase_u(r#""\U0041""#, vec![], Some(JsonParseError::Parse("invalid escape in string literal", Location::start())))]
    #[case::string_literal_unicode_uppercase(r#""\uABCD""#, vec![JsonReadToken::StringLiteral("\u{abcd}")], None)]
    #[case::string_literal_unicode_mixed_case_1(r#""\uaBcD""#, vec![JsonReadToken::StringLiteral("\u{abcd}")], None)]
    #[case::string_literal_unicode_mixed_case_2(r#""\uAbCd""#, vec![JsonReadToken::StringLiteral("\u{abcd}")], None)]

    #[case::null_wrong_continuation_1("nul", vec![], Some(JsonParseError::Parse("incomplete null literal", Location::start())))]
    #[case::null_wrong_continuation_2("nxll", vec![], Some(JsonParseError::Parse("incomplete null literal", Location::start())))]
    #[case::null_wrong_continuation_3("nUll", vec![], Some(JsonParseError::Parse("incomplete null literal", Location::start())))]
    #[case::null_wrong_continuation_4("nuxl", vec![], Some(JsonParseError::Parse("incomplete null literal", Location::start())))]
    #[case::null_wrong_continuation_5("nuLl", vec![], Some(JsonParseError::Parse("incomplete null literal", Location::start())))]
    #[case::null_wrong_continuation_6("nulx", vec![], Some(JsonParseError::Parse("incomplete null literal", Location::start())))]
    #[case::null_wrong_continuation_7("nulL", vec![], Some(JsonParseError::Parse("incomplete null literal", Location::start())))]
    #[case::null_uppercase("Null", vec![], Some(JsonParseError::Parse("invalid JSON literal", Location::start())))]
    #[case::null_uppercase_2("NULL", vec![], Some(JsonParseError::Parse("invalid JSON literal", Location::start())))]

    #[case::true_wrong_continuation_1("tru", vec![], Some(JsonParseError::Parse("incomplete true literal", Location::start())))]
    #[case::true_wrong_continuation_2("txue", vec![], Some(JsonParseError::Parse("incomplete true literal", Location::start())))]
    #[case::true_wrong_continuation_3("tRue", vec![], Some(JsonParseError::Parse("incomplete true literal", Location::start())))]
    #[case::true_wrong_continuation_4("trxe", vec![], Some(JsonParseError::Parse("incomplete true literal", Location::start())))]
    #[case::true_wrong_continuation_5("trUe", vec![], Some(JsonParseError::Parse("incomplete true literal", Location::start())))]
    #[case::true_wrong_continuation_6("trux", vec![], Some(JsonParseError::Parse("incomplete true literal", Location::start())))]
    #[case::true_wrong_continuation_7("truE", vec![], Some(JsonParseError::Parse("incomplete true literal", Location::start())))]
    #[case::true_uppercase_1("True", vec![], Some(JsonParseError::Parse("invalid JSON literal", Location::start())))]
    #[case::true_uppercase_2("TRUE", vec![], Some(JsonParseError::Parse("invalid JSON literal", Location::start())))]

    #[case::false_wrong_continuation_1("fals", vec![], Some(JsonParseError::Parse("incomplete false literal", Location::start())))]
    #[case::false_wrong_continuation_2("fxlse", vec![], Some(JsonParseError::Parse("incomplete false literal", Location::start())))]
    #[case::false_wrong_continuation_3("fAlse", vec![], Some(JsonParseError::Parse("incomplete false literal", Location::start())))]
    #[case::false_wrong_continuation_4("faxse", vec![], Some(JsonParseError::Parse("incomplete false literal", Location::start())))]
    #[case::false_wrong_continuation_5("faLse", vec![], Some(JsonParseError::Parse("incomplete false literal", Location::start())))]
    #[case::false_wrong_continuation_6("falxe", vec![], Some(JsonParseError::Parse("incomplete false literal", Location::start())))]
    #[case::false_wrong_continuation_7("falSe", vec![], Some(JsonParseError::Parse("incomplete false literal", Location::start())))]
    #[case::false_wrong_continuation_8("falsx", vec![], Some(JsonParseError::Parse("incomplete false literal", Location::start())))]
    #[case::false_wrong_continuation_9("falsE", vec![], Some(JsonParseError::Parse("incomplete false literal", Location::start())))]
    #[case::false_uppercase_1("False", vec![], Some(JsonParseError::Parse("invalid JSON literal", Location::start())))]
    #[case::false_uppercase_2("FALSE", vec![], Some(JsonParseError::Parse("invalid JSON literal", Location::start())))]

    #[case::object_end_just_comma(r#"{, }"#, vec![JsonReadToken::StartObject], Some(JsonParseError::Parse("unexpected comma", Location::start())))]
    #[case::object_end_trailing_comma(r#"{"a": null, }"#, vec![JsonReadToken::StartObject, JsonReadToken::Key("a"), JsonReadToken::NullLiteral], Some(JsonParseError::Parse("trailing comma", Location::start())))]
    #[case::object_end_after_key(r#"{"a": }"#, vec![JsonReadToken::StartObject, JsonReadToken::Key("a")], Some(JsonParseError::Parse("key without a value", Location::start())))]
    #[case::array_end_just_comma(r#"[, ]"#, vec![JsonReadToken::StartArray], Some(JsonParseError::Parse("unexpected comma", Location::start())))]
    #[case::array_end_trailing_comma(r#"[null, ]"#, vec![JsonReadToken::StartArray, JsonReadToken::NullLiteral], Some(JsonParseError::Parse("trailing comma", Location::start())))]
    #[case::array_end_after_key(r#"["a": ]"#, vec![JsonReadToken::StartArray, JsonReadToken::Key("a")], Some(JsonParseError::Parse("key without a value", Location::start())))]

    #[case::missing_comma_null(r#"[null null]"#, vec![JsonReadToken::StartArray, JsonReadToken::NullLiteral], Some(JsonParseError::Parse("missing comma", Location::start())))]
    #[case::missing_comma_true(r#"[null true]"#, vec![JsonReadToken::StartArray, JsonReadToken::NullLiteral], Some(JsonParseError::Parse("missing comma", Location::start())))]
    #[case::missing_comma_false(r#"[null false]"#, vec![JsonReadToken::StartArray, JsonReadToken::NullLiteral], Some(JsonParseError::Parse("missing comma", Location::start())))]
    #[case::missing_comma_number(r#"[null 123]"#, vec![JsonReadToken::StartArray, JsonReadToken::NullLiteral], Some(JsonParseError::Parse("missing comma", Location::start())))]
    #[case::missing_comma_string(r#"[null "abc"]"#, vec![JsonReadToken::StartArray, JsonReadToken::NullLiteral], Some(JsonParseError::Parse("missing comma", Location::start())))]
    #[case::missing_comma_object(r#"[null {}]"#, vec![JsonReadToken::StartArray, JsonReadToken::NullLiteral], Some(JsonParseError::Parse("missing comma", Location::start())))]
    #[case::missing_comma_array(r#"[null []]"#, vec![JsonReadToken::StartArray, JsonReadToken::NullLiteral], Some(JsonParseError::Parse("missing comma", Location::start())))]
    #[case::missing_comma_key(r#"{"a": null "b": 1}"#, vec![JsonReadToken::StartObject, JsonReadToken::Key("a"), JsonReadToken::NullLiteral], Some(JsonParseError::Parse("missing comma", Location::start())))]
    #[case::key_after_key(r#"{"a": "b": 1}"#, vec![JsonReadToken::StartObject, JsonReadToken::Key("a")], Some(JsonParseError::Parse("two keys without value", Location::start())))]
    #[case::comma_after_key(r#"{"a": , "b": 1}"#, vec![JsonReadToken::StartObject, JsonReadToken::Key("a")], Some(JsonParseError::Parse("unexpected comma", Location::start())))]

    #[case::object_comma_after_comma(r#"{"a": null, ,}"#, vec![JsonReadToken::StartObject, JsonReadToken::Key("a"), JsonReadToken::NullLiteral], Some(JsonParseError::Parse("unexpected comma", Location::start())))]
    #[case::array_comma_after_comma(r#"[ null, ,]"#, vec![JsonReadToken::StartArray, JsonReadToken::NullLiteral], Some(JsonParseError::Parse("unexpected comma", Location::start())))]

    #[case::object(r#"{ "a": 1, "b": true, "c": "xyz" }"#, vec![
        JsonReadToken::StartObject,
        JsonReadToken::Key("a"),
        JsonReadToken::NumberLiteral(JsonNumber("1")),
        JsonReadToken::Key("b"),
        JsonReadToken::BooleanLiteral(true),
        JsonReadToken::Key("c"),
        JsonReadToken::StringLiteral("xyz"),
        JsonReadToken::EndObject,
    ], None)]
    #[case::array(r#"[ 6, "xy", true, null ]"#, vec![
        JsonReadToken::StartArray,
        JsonReadToken::NumberLiteral(JsonNumber("6")),
        JsonReadToken::StringLiteral("xy"),
        JsonReadToken::BooleanLiteral(true),
        JsonReadToken::NullLiteral,
        JsonReadToken::EndArray,
    ], None)]
    #[case::complex(r#"{"abc":"yo","xyz":"yo","aaaa":["111","11",{},[],null,true,false,-23987,23987,23.235,null,null,23.235e-1,null,null],"ooo":{"lll":"whatever","ar":[]}}"#, vec![
        JsonReadToken::StartObject,
        JsonReadToken::Key("abc"),
        JsonReadToken::StringLiteral("yo"),
        JsonReadToken::Key("xyz"),
        JsonReadToken::StringLiteral("yo"),
        JsonReadToken::Key("aaaa"),
        JsonReadToken::StartArray,
        JsonReadToken::StringLiteral("111"),
        JsonReadToken::StringLiteral("11"),
        JsonReadToken::StartObject,
        JsonReadToken::EndObject,
        JsonReadToken::StartArray,
        JsonReadToken::EndArray,
        JsonReadToken::NullLiteral,
        JsonReadToken::BooleanLiteral(true),
        JsonReadToken::BooleanLiteral(false),
        JsonReadToken::NumberLiteral(JsonNumber("-23987")),
        JsonReadToken::NumberLiteral(JsonNumber("23987")),
        JsonReadToken::NumberLiteral(JsonNumber("23.235")),
        JsonReadToken::NullLiteral,
        JsonReadToken::NullLiteral,
        JsonReadToken::NumberLiteral(JsonNumber("23.235e-1")),
        JsonReadToken::NullLiteral,
        JsonReadToken::NullLiteral,
        JsonReadToken::EndArray,
        JsonReadToken::Key("ooo"),
        JsonReadToken::StartObject,
        JsonReadToken::Key("lll"),
        JsonReadToken::StringLiteral("whatever"),
        JsonReadToken::Key("ar"),
        JsonReadToken::StartArray,
        JsonReadToken::EndArray,
        JsonReadToken::EndObject,
        JsonReadToken::EndObject,
    ], None)]

    fn test_parse(#[case] input: &str, #[case] expected: Vec<JsonReadToken>, #[case] expected_error: Option<JsonParseError<std::io::Error>>) {
        let input_with_whitespace = format!(" \r\n\t{} \r\n\t", input);

        {
            let mut r = Cursor::new(input.as_bytes());
            let mut json_reader = JsonReader::new(64, &mut r);
            for evt in &expected {
                let parsed_evt = json_reader.next();
                assert_eq!(&parsed_evt.unwrap(), evt);
            }
            if let Some(expected_error) = &expected_error {
                match json_reader.next() {
                    Ok(_) => panic!("expected error but was ok: {}", expected_error),
                    Err(e) => assert_is_similar_error(&e, expected_error),
                }
            }
            else {
                assert_eq!(json_reader.next().unwrap(), JsonReadToken::EndOfStream);
            }
        }
        {
            let mut r = Cursor::new(input_with_whitespace.as_bytes());
            let mut json_reader = JsonReader::new(64, &mut r);
            for evt in &expected {
                assert_eq!(&json_reader.next().unwrap(), evt);
            }
            if let Some(expected_error) = &expected_error {
                match json_reader.next() {
                    Ok(_) => panic!("expected error but was ok: {}", expected_error),
                    Err(e) => assert_is_similar_error(&e, expected_error),
                }
            }
            else {
                assert_eq!(json_reader.next().unwrap(), JsonReadToken::EndOfStream);
            }
        }
    }

    #[test]
    fn test_provided_buffer_fits() -> Result<(), JsonParseError<io::Error>> {
        let mut r = Cursor::new(b"123".to_vec());
        let mut reader = JsonReader::new(8, &mut r);
        assert_eq!(reader.next()?, JsonReadToken::NumberLiteral(JsonNumber("123")));
        assert_eq!(reader.next()?, JsonReadToken::EndOfStream);
        Ok(())
    }

    #[test]
    fn test_provided_buffer_overflow() -> Result<(), JsonParseError<io::Error>> {
        let mut r = Cursor::new(b"\"123 123 x\"".to_vec());
        let mut reader = JsonReader::new(8, &mut r);
        match reader.next() {
            Ok(_) => panic!("expected an error"),
            Err(e) => assert_is_similar_error(&e, &JsonParseError::BufferOverflow(Location::start())),
        }
        Ok(())
    }

    #[rstest]
    #[case::simple("1", Some(1), Some(1), 1.0, 1.0)]
    #[case::big("1345678345", Some(1345678345), Some(1345678345), 1345678345.0, 1345678345.0)]
    #[case::bigger("3345678345", Some(3345678345), None, 3345678345.0, 3345678345.0)]
    #[case::too_big("13456783459", None, None, 13456783459.0, 13456783459.0)]
    #[case::negative("-1", None, Some(-1), -1.0, -1.0)]
    #[case::fract("1.0", None, None, 1.0, 1.0)]
    #[case::exp("1e3", None, None, 1e3, 1e3)]
    #[case::neg_exp("1e-3", None, None, 1e-3, 1e-3)]
    #[case::pos_exp("1e+3", None, None, 1e3, 1e3)]
    #[case::fract_exp("1.23e3", None, None, 1230.0, 1230.0)]
    #[case::fract_neg_exp("1.23e-3", None, None, 1.23e-3, 1.23e-3)]
    #[case::fract_pos_exp("1.23e+3", None, None, 1.23e3, 1.23e3)]
    fn test_json_number_parse(#[case] s: &str, #[case] expected_u32: Option<u32>, #[case] expected_i32: Option<i32>, #[case] expected_f64: f64, #[case] expected_f32: f32) {
        let n = JsonNumber(s);

        {
            let parsed = n.parse::<u32>();
            match expected_u32 {
                Some(e) => assert_eq!(e, parsed.unwrap()),
                None => assert!(parsed.is_err()),
            }
        }
        {
            let parsed = n.parse::<i32>();
            match expected_i32 {
                Some(e) => assert_eq!(e, parsed.unwrap()),
                None => assert!(parsed.is_err()),
            }
        }
        {
            let parsed = n.parse::<f64>();
            assert_eq!(expected_f64, parsed.unwrap());
        }
        {
            let parsed = n.parse::<f32>();
            assert_eq!(expected_f32, parsed.unwrap());
        }
    }


    #[rstest]
    #[case::simple(Location::start(), vec![b'a'], Location { offset: 1, line: 1, column: 2,})]
    #[case::cr(Location::start(), vec![b'\r'], Location { offset: 1, line: 1, column: 2,})]
    #[case::tab(Location::start(), vec![b'\t'], Location { offset: 1, line: 1, column: 2,})]
    #[case::nl(Location::start(), vec![b'\n'], Location { offset: 1, line: 2, column: 1,})]
    #[case::in_line(Location::start(), vec![b'\r', b'\n', b'\n', b'x', b'y'], Location { offset: 5, line: 3, column: 3,})]
    #[case::sequence(Location::start(), vec![b'a', b'b', b'\n', b'x', b'\n'], Location { offset: 5, line: 3, column: 1,})]
    fn test_location_after_byte(#[case] mut initial: Location, #[case] bytes: Vec<u8>, #[case] expected: Location) {
        for byte in bytes {
            initial.after_byte(byte);
        }
        assert_eq!(initial, expected);
    }


    #[rstest]
    #[case::key(r#""abc": null"#, Some(Some("abc")))]
    #[case::other_key(r#""xyz": null"#, Some(Some("xyz")))]
    #[case::end_object(r#"}"#, Some(None))]
    #[case::null(r#"null"#, None)]
    #[case::bool(r#"true"#, None)]
    #[case::number(r#"1"#, None)]
    #[case::string(r#""a""#, None)]
    #[case::start_object(r#"{"#, None)]
    #[case::start_array(r#"["#, None)]
    #[case::end_array(r#"]"#, None)]
    fn test_expect_key(#[case] json: &str, #[case] expected: Option<Option<&str>>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_key() {
            Ok(actual) => assert_eq!(actual, expected.unwrap()),
            Err(JsonParseError::Parse(_, _)) => assert!(expected.is_none()),
            Err(e) => panic!("unexpected error: {}", e)
        }
    }

    #[rstest]
    #[case::simple("1", Ok(1))]
    #[case::other_number("500", Err(JsonParseError::Parse("invalid number", Location::start())))]
    #[case::null("null", Err(JsonParseError::Parse("", Location::start())))]
    #[case::string("\"abc\"", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::bool("true", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_array("]", Err(JsonParseError::Parse("", Location::start())))]
    fn test_expect_number(#[case] json: &str, #[case] expected_num: JsonParseResult<u8, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_number::<u8>() {
            Ok(n) => assert_eq!(n, expected_num.unwrap()),
            Err(act_e) => match expected_num {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::simple("1", Ok(Some(1)))]
    #[case::other_number("500", Err(JsonParseError::Parse("invalid number", Location::start())))]
    #[case::null("null", Err(JsonParseError::Parse("", Location::start())))]
    #[case::string("\"abc\"", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::bool("true", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_array("]", Ok(None))]
    fn test_expect_number_or_end_array(#[case] json: &str, #[case] expected_num: JsonParseResult<Option<u8>, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_number_or_end_array::<u8>() {
            Ok(n) => assert_eq!(n, expected_num.unwrap()),
            Err(act_e) => match expected_num {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::simple("1", Ok(Some(1)))]
    #[case::other_number("500", Err(JsonParseError::Parse("invalid number", Location::start())))]
    #[case::null("null", Ok(None))]
    #[case::string("\"abc\"", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::bool("true", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_array("]", Err(JsonParseError::Parse("", Location::start())))]
    fn test_expect_opt_number(#[case] json: &str, #[case] expected_num: JsonParseResult<Option<u8>, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_opt_number::<u8>() {
            Ok(n) => assert_eq!(n, expected_num.unwrap()),
            Err(act_e) => match expected_num {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::simple("1", Ok(Some(Some(1))))]
    #[case::other_number("500", Err(JsonParseError::Parse("invalid number", Location::start())))]
    #[case::null("null", Ok(Some(None)))]
    #[case::string("\"abc\"", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::bool("true", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_array("]", Ok(None))]
    fn test_expect_opt_number_or_end_array(#[case] json: &str, #[case] expected_num: JsonParseResult<Option<Option<u8>>, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_opt_number_or_end_array::<u8>() {
            Ok(n) => assert_eq!(n, expected_num.unwrap()),
            Err(act_e) => match expected_num {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::simple(" 123.45 ", Ok(JsonNumber("123.45")))]
    #[case::null("null", Err(JsonParseError::Parse("", Location::start())))]
    #[case::string("\"abc\"", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::bool("true", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_array("]", Err(JsonParseError::Parse("", Location::start())))]
    fn test_expect_raw_number(#[case] json: &str, #[case] expected_num: JsonParseResult<JsonNumber, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_raw_number() {
            Ok(n) => assert_eq!(n, expected_num.unwrap()),
            Err(act_e) => match expected_num {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::simple(" 123.45 ", Ok(Some(JsonNumber("123.45"))))]
    #[case::null("null", Err(JsonParseError::Parse("", Location::start())))]
    #[case::string("\"abc\"", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::bool("true", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_array("]", Ok(None))]
    fn test_expect_raw_number_or_end_array(#[case] json: &str, #[case] expected_num: JsonParseResult<Option<JsonNumber>, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_raw_number_or_end_array() {
            Ok(n) => assert_eq!(n, expected_num.unwrap()),
            Err(act_e) => match expected_num {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::number(" 5 ", Ok(Some(JsonNumber("5"))))]
    #[case::null(" null ", Ok(None))]
    #[case::boolean(" ] ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::boolean(" true ", Err(JsonParseError::Parse("", Location::start())))]
    fn test_expect_opt_raw_number(#[case] json: &str, #[case] expected_num: JsonParseResult<Option<JsonNumber>, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_opt_raw_number() {
            Ok(o) => assert_eq!(o, expected_num.unwrap()),
            Err(act_e) => match expected_num {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::number(" 5 ", Ok(Some(Some(JsonNumber("5")))))]
    #[case::null(" null ", Ok(Some(None)))]
    #[case::null(" ] ", Ok(None))]
    #[case::boolean(" true ", Err(JsonParseError::Parse("", Location::start())))]
    fn test_expect_opt_raw_number_or_end_array(#[case] json: &str, #[case] expected_num: JsonParseResult<Option<Option<JsonNumber>>, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_opt_raw_number_or_end_array() {
            Ok(o) => assert_eq!(o, expected_num.unwrap()),
            Err(act_e) => match expected_num {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::simple("\"qrs\"", Ok("qrs"))]
    #[case::null("null", Err(JsonParseError::Parse("", Location::start())))]
    #[case::number("12", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::bool("true", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_array("]", Err(JsonParseError::Parse("", Location::start())))]
    fn test_expect_string(#[case] json: &str, #[case] expected: JsonParseResult<&str, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_string() {
            Ok(n) => assert_eq!(n, expected.unwrap()),
            Err(act_e) => match expected {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::simple("\"qrs\"", Ok(Some("qrs")))]
    #[case::null("null", Err(JsonParseError::Parse("", Location::start())))]
    #[case::number("12", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::bool("true", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_array("]", Ok(None))]
    fn test_expect_string_or_end_array(#[case] json: &str, #[case] expected: JsonParseResult<Option<&str>, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_string_or_end_array() {
            Ok(n) => assert_eq!(n, expected.unwrap()),
            Err(act_e) => match expected {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::simple("\"rst\"", Ok(Some("rst")))]
    #[case::null("null", Ok(None))]
    #[case::number("12", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::bool("true", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_array("]", Err(JsonParseError::Parse("", Location::start())))]
    fn test_expect_opt_string(#[case] json: &str, #[case] expected: JsonParseResult<Option<&str>, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_opt_string() {
            Ok(n) => assert_eq!(n, expected.unwrap()),
            Err(act_e) => match expected {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::simple("\"rst\"", Ok(Some(Some("rst"))))]
    #[case::null("null", Ok(Some(None)))]
    #[case::number("12", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::bool("true", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_array("]", Ok(None))]
    fn test_expect_opt_string_or_end_array(#[case] json: &str, #[case] expected: JsonParseResult<Option<Option<&str>>, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_opt_string_or_end_array() {
            Ok(n) => assert_eq!(n, expected.unwrap()),
            Err(act_e) => match expected {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::bool_true("true", Ok(true))]
    #[case::bool_false("false", Ok(false))]
    #[case::null("null", Err(JsonParseError::Parse("", Location::start())))]
    #[case::string("\"a\"", Err(JsonParseError::Parse("", Location::start())))]
    #[case::number("12", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_array("]", Err(JsonParseError::Parse("", Location::start())))]
    fn test_expect_bool(#[case] json: &str, #[case] expected: JsonParseResult<bool, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_bool() {
            Ok(n) => assert_eq!(n, expected.unwrap()),
            Err(act_e) => match expected {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::bool_true("true", Ok(Some(true)))]
    #[case::bool_false("false", Ok(Some(false)))]
    #[case::null("null", Err(JsonParseError::Parse("", Location::start())))]
    #[case::string("\"a\"", Err(JsonParseError::Parse("", Location::start())))]
    #[case::number("12", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_array("]", Ok(None))]
    fn test_expect_bool_or_end_array(#[case] json: &str, #[case] expected: JsonParseResult<Option<bool>, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_bool_or_end_array() {
            Ok(n) => assert_eq!(n, expected.unwrap()),
            Err(act_e) => match expected {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::bool_true("true", Ok(Some(true)))]
    #[case::bool_false("false", Ok(Some(false)))]
    #[case::null("null", Ok(None))]
    #[case::string("\"x\"", Err(JsonParseError::Parse("", Location::start())))]
    #[case::number("12", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_array("]", Err(JsonParseError::Parse("", Location::start())))]
    fn test_expect_opt_bool(#[case] json: &str, #[case] expected: JsonParseResult<Option<bool>, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_opt_bool() {
            Ok(n) => assert_eq!(n, expected.unwrap()),
            Err(act_e) => match expected {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::bool_true("true", Ok(Some(Some(true))))]
    #[case::bool_false("false", Ok(Some(Some(false))))]
    #[case::null("null", Ok(Some(None)))]
    #[case::string("\"x\"", Err(JsonParseError::Parse("", Location::start())))]
    #[case::number("12", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_array("]", Ok(None))]
    fn test_expect_opt_bool_or_end_array(#[case] json: &str, #[case] expected: JsonParseResult<Option<Option<bool>>, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_opt_bool_or_end_array() {
            Ok(n) => assert_eq!(n, expected.unwrap()),
            Err(act_e) => match expected {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::null("null", Err(JsonParseError::Parse("", Location::start())))]
    #[case::bool("true", Err(JsonParseError::Parse("", Location::start())))]
    #[case::string("\"a\"", Err(JsonParseError::Parse("", Location::start())))]
    #[case::number("12", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Ok(()))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_array("]", Err(JsonParseError::Parse("", Location::start())))]
    fn test_expect_start_object(#[case] json: &str, #[case] expected: JsonParseResult<(), io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_start_object() {
            Ok(n) => assert_eq!(n, expected.unwrap()),
            Err(act_e) => match expected {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::null("null", Err(JsonParseError::Parse("", Location::start())))]
    #[case::bool("true", Err(JsonParseError::Parse("", Location::start())))]
    #[case::string("\"a\"", Err(JsonParseError::Parse("", Location::start())))]
    #[case::number("12", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Ok(Some(())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_array("]", Ok(None))]
    fn test_expect_start_object_or_end_array(#[case] json: &str, #[case] expected: JsonParseResult<Option<()>, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_start_object_or_end_array() {
            Ok(n) => assert_eq!(n, expected.unwrap()),
            Err(act_e) => match expected {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::null("null", Err(JsonParseError::Parse("", Location::start())))]
    #[case::bool("true", Err(JsonParseError::Parse("", Location::start())))]
    #[case::string("\"a\"", Err(JsonParseError::Parse("", Location::start())))]
    #[case::number("12", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_object("}", Ok(()))]
    #[case::start_array("[", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_array("]", Err(JsonParseError::Parse("", Location::start())))]
    fn test_expect_end_object(#[case] json: &str, #[case] expected: JsonParseResult<(), io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_end_object() {
            Ok(n) => assert_eq!(n, expected.unwrap()),
            Err(act_e) => match expected {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::bool("false", Err(JsonParseError::Parse("", Location::start())))]
    #[case::null("null", Ok(None))]
    #[case::string("\"x\"", Err(JsonParseError::Parse("", Location::start())))]
    #[case::number("12", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Ok(Some(())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_array("]", Err(JsonParseError::Parse("", Location::start())))]
    fn test_expect_opt_start_object(#[case] json: &str, #[case] expected: JsonParseResult<Option<()>, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_opt_start_object() {
            Ok(n) => assert_eq!(n, expected.unwrap()),
            Err(act_e) => match expected {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::bool("false", Err(JsonParseError::Parse("", Location::start())))]
    #[case::null("null", Ok(Some(None)))]
    #[case::string("\"x\"", Err(JsonParseError::Parse("", Location::start())))]
    #[case::number("12", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Ok(Some(Some(()))))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_array("]", Ok(None))]
    fn test_expect_opt_start_object_or_end_array(#[case] json: &str, #[case] expected: JsonParseResult<Option<Option<()>>, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_opt_start_object_or_end_array() {
            Ok(n) => assert_eq!(n, expected.unwrap()),
            Err(act_e) => match expected {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::null("null", Err(JsonParseError::Parse("", Location::start())))]
    #[case::bool("true", Err(JsonParseError::Parse("", Location::start())))]
    #[case::string("\"a\"", Err(JsonParseError::Parse("", Location::start())))]
    #[case::number("12", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Ok(()))]
    #[case::end_array("]", Err(JsonParseError::Parse("", Location::start())))]
    fn test_expect_start_array(#[case] json: &str, #[case] expected: JsonParseResult<(), io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_start_array() {
            Ok(n) => assert_eq!(n, expected.unwrap()),
            Err(act_e) => match expected {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::null("null", Err(JsonParseError::Parse("", Location::start())))]
    #[case::bool("true", Err(JsonParseError::Parse("", Location::start())))]
    #[case::string("\"a\"", Err(JsonParseError::Parse("", Location::start())))]
    #[case::number("12", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Ok(Some(())))]
    #[case::end_array("]", Ok(None))]
    fn test_expect_start_array_or_end_array(#[case] json: &str, #[case] expected: JsonParseResult<Option<()>, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_start_array_or_end_array() {
            Ok(n) => assert_eq!(n, expected.unwrap()),
            Err(act_e) => match expected {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::null("null", Err(JsonParseError::Parse("", Location::start())))]
    #[case::bool("true", Err(JsonParseError::Parse("", Location::start())))]
    #[case::string("\"a\"", Err(JsonParseError::Parse("", Location::start())))]
    #[case::number("12", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_array("]", Ok(()))]
    fn test_expect_end_array(#[case] json: &str, #[case] expected: JsonParseResult<(), io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_end_array() {
            Ok(n) => assert_eq!(n, expected.unwrap()),
            Err(act_e) => match expected {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::bool("false", Err(JsonParseError::Parse("", Location::start())))]
    #[case::null("null", Ok(None))]
    #[case::string("\"x\"", Err(JsonParseError::Parse("", Location::start())))]
    #[case::number("12", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Ok(Some(())))]
    #[case::end_array("]", Err(JsonParseError::Parse("", Location::start())))]
    fn test_expect_opt_start_array(#[case] json: &str, #[case] expected: JsonParseResult<Option<()>, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_opt_start_array() {
            Ok(n) => assert_eq!(n, expected.unwrap()),
            Err(act_e) => match expected {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[rstest]
    #[case::bool("false", Err(JsonParseError::Parse("", Location::start())))]
    #[case::null("null", Ok(Some(None)))]
    #[case::string("\"x\"", Err(JsonParseError::Parse("", Location::start())))]
    #[case::number("12", Err(JsonParseError::Parse("", Location::start())))]
    #[case::key("\"abc\": ", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_object("{", Err(JsonParseError::Parse("", Location::start())))]
    #[case::end_object("}", Err(JsonParseError::Parse("", Location::start())))]
    #[case::start_array("[", Ok(Some(Some(()))))]
    #[case::end_array("]", Ok(None))]
    fn test_expect_opt_start_array_or_end_array(#[case] json: &str, #[case] expected: JsonParseResult<Option<Option<()>>, io::Error>) {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.expect_opt_start_array_or_end_array() {
            Ok(n) => assert_eq!(n, expected.unwrap()),
            Err(act_e) => match expected {
                Ok(_) => panic!("unexpected error: {}", act_e),
                Err(exp_e) => assert_is_similar_error(&act_e, &exp_e),
            }
        }
    }

    #[test]
    fn test_with_lenient_comma() {
        let json = r#"
        { "a": 1}
        { "a": 2}
        "#;

        {
            let mut r = Cursor::new(json.as_bytes());
            let result = try_read_json_lines(&mut JsonReader::new(64, &mut r));
            assert!(result.is_err());
        }

        {
            let mut r = Cursor::new(json.as_bytes());
            let result = try_read_json_lines(&mut JsonReader::new_with_lenient_comma_handling(64, &mut r));
            assert_eq!(result.unwrap(), vec![1, 2]);
        }
    }

    fn try_read_json_lines<R: Read>(json_reader: &mut JsonReader<Vec<u8>, R>) -> JsonParseResult<Vec<u32>, io::Error> {
        let mut result = Vec::new();
        while json_reader.next()? == JsonReadToken::StartObject {
            loop {
                match json_reader.expect_key()? {
                    Some("a") => result.push( json_reader.expect_number()?),
                    Some(_) => json_reader.skip_value()?,
                    None => break,
                }
            }
        }
        Ok(result)
    }

    #[rstest]
    #[case::end_object_empty("}, 77", false)]
    #[case::end_object_simple(r#" "a": 10, "b": null }, 77"#, false)]
    #[case::end_object_nested(r#" "a": 10, "x": { "q": 99, "r": [1, 2, 3] }, "b": null }, 77"#, false)]
    #[case::end_array_empty("], 77", false)]
    #[case::end_array_simple(r#"99, "abc", null, true], 77"#, false)]
    #[case::end_array_nested(r#"99, [1, [], true, {"abc": { "xyz": [1, 2, 3]}}], "abc", null, true], 77"#, false)]
    #[case::number("1, 77", true)]
    #[case::boolean("true, 77", true)]
    #[case::null("null, 77", true)]
    fn test_skip_to_end_of_current_scope(#[case] json: &str, #[case] should_fail: bool) -> JsonParseResult<(), io::Error> {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.skip_to_end_of_current_scope() {
            Ok(_) => {
                assert!(!should_fail);
                assert_eq!(77, json_reader.expect_number::<u32>()?);
            }
            Err(_) => {
                assert!(should_fail);
            }
        }
        Ok(())
    }

    #[rstest]
    #[case::number(r#"123, 77"#, false)]
    #[case::string(r#""abc", 77"#, false)]
    #[case::boolean(r#"true, 77"#, false)]
    #[case::null(r#"null, 77"#, false)]
    #[case::object_empty(r#"{}, 77"#, false)]
    #[case::object_simple(r#"{ "a": 10, "b": null }, 77"#, false)]
    #[case::object_nested(r#"{ "a": 10, "x": { "q": 99, "r": [1, 2, 3] }, "b": null }, 77"#, false)]
    #[case::array_empty("[], 77", false)]
    #[case::array_simple(r#"[99, "abc", null, true], 77"#, false)]
    #[case::array_nested(r#"[99, [1, [], true, {"abc": { "xyz": [1, 2, 3]}}], "abc", null, true], 77"#, false)]
    fn test_skip_value(#[case] json: &str, #[case] should_fail: bool) -> JsonParseResult<(), io::Error> {
        let mut r = Cursor::new(json.as_bytes());
        let mut json_reader = JsonReader::new(64, &mut r);
        match json_reader.skip_value() {
            Ok(_) => {
                assert!(!should_fail);
                assert_eq!(77, json_reader.expect_number::<u32>()?);
            }
            Err(_) => {
                assert!(should_fail);
            }
        }
        Ok(())
    }
}