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//! JSON writer variant which is easier to use than [`JsonWriter`]
//!
//! The main entrypoint is [`SimpleJsonWriter`], all other structs and traits
//! are used by it for writing certain JSON value types.
//!
//! ----
//!
//! **🔬 Experimental**\
//! This API and the naming is currently experimental, please provide feedback [here](https://github.com/Marcono1234/struson/issues/34).
//! Any feedback is appreciated!
use std::{error::Error, io::Write};
use self::error_safe_writer::{error_from_stored, ErrorSafeJsonWriter};
use crate::writer::{
FiniteNumber, FloatingPointNumber, JsonNumberError, JsonStreamWriter, JsonWriter,
StringValueWriter as AdvancedStringValueWriter,
};
type IoError = std::io::Error;
/// Writer for a JSON value
pub trait ValueWriter<J: JsonWriter> {
/// Writes a JSON null value
fn write_null(self) -> Result<(), IoError>;
/// Writes a JSON boolean value
fn write_bool(self, value: bool) -> Result<(), IoError>;
/// Writes a JSON string value
///
/// For writing a large string value in a streaming way, use
/// [`write_string_with_writer`](Self::write_string_with_writer).
fn write_string(self, value: &str) -> Result<(), IoError>;
/// Writes a JSON string value using a [`Write`]
///
/// The function `f` is called with a writer as argument which allows writing the
/// JSON string value. Characters will be automatically escaped if necessary, for
/// example `"` will be written as `\"`.
///
/// This method is mainly intended for writing large JSON string values in a
/// streaming way; for all other cases prefer [`write_string`](Self::write_string).
///
/// # Examples
/// ```
/// # use struson::writer::simple::*;
/// # use std::io::Write;
/// let mut writer = Vec::<u8>::new();
/// let json_writer = SimpleJsonWriter::new(&mut writer);
/// json_writer.write_string_with_writer(|mut string_writer| {
/// // Can use regular `Write` methods
/// string_writer.write_all(b"some text")?;
/// // Or `write_str` method
/// string_writer.write_str(" with \" quote")?;
/// Ok(())
/// })?;
///
/// let json = String::from_utf8(writer)?;
/// assert_eq!(
/// json,
/// "\"some text with \\\" quote\""
/// );
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// # Writer errors
/// The error behavior of the string writer differs from the guarantees made by [`Write`]:
/// - if an error is returned there are no guarantees about if or how many bytes have been
/// written
/// - if an error occurs, processing should be aborted, regardless of the kind of the error;
/// trying to use the string writer or the original JSON writer afterwards will lead
/// to unspecified behavior
fn write_string_with_writer(
self,
f: impl FnOnce(StringValueWriter<'_>) -> Result<(), Box<dyn Error>>,
) -> Result<(), Box<dyn Error>>;
/// Writes a JSON number value
fn write_number<N: FiniteNumber>(self, value: N) -> Result<(), IoError>;
/// Writes a floating point JSON number value
///
/// Returns an error if the number is non-finite and therefore cannot be written
/// as JSON number value.
fn write_fp_number<N: FloatingPointNumber>(self, value: N) -> Result<(), JsonNumberError>;
/// Writes the string representation of a JSON number value
///
/// Returns an error if the string is not a valid JSON number value.
fn write_number_string(self, value: &str) -> Result<(), JsonNumberError>;
/// Serializes a Serde [`Serialize`](serde::ser::Serialize) as next value
///
/// This method is part of the optional Serde integration feature, see the
/// [`serde` module](crate::serde) of this crate for more information.
///
/// # Examples
/// ```
/// # use struson::writer::simple::*;
/// # use serde::*;
/// let mut writer = Vec::<u8>::new();
/// let json_writer = SimpleJsonWriter::new(&mut writer);
///
/// #[derive(Serialize)]
/// struct MyStruct {
/// text: String,
/// number: u64,
/// }
///
/// let value = MyStruct {
/// text: "some text".to_owned(),
/// number: 5,
/// };
/// json_writer.write_serialize(&value)?;
///
/// let json = String::from_utf8(writer)?;
/// assert_eq!(
/// json,
/// r#"{"text":"some text","number":5}"#
/// );
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[cfg(feature = "serde")]
fn write_serialize<S: serde::ser::Serialize>(
self,
value: &S,
) -> Result<(), crate::serde::SerializerError>;
/// Writes a JSON array
///
/// # Examples
/// ```
/// # use struson::writer::simple::*;
/// let mut writer = Vec::<u8>::new();
/// let json_writer = SimpleJsonWriter::new(&mut writer);
/// json_writer.write_array(|array_writer| {
/// array_writer.write_number(1)?;
/// array_writer.write_bool(true)?;
/// Ok(())
/// })?;
///
/// let json = String::from_utf8(writer)?;
/// assert_eq!(json, "[1,true]");
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
fn write_array(
self,
f: impl FnOnce(&mut ArrayWriter<'_, J>) -> Result<(), Box<dyn Error>>,
) -> Result<(), Box<dyn Error>>;
/// Writes a JSON object
///
/// # Examples
/// ```
/// # use struson::writer::simple::*;
/// let mut writer = Vec::<u8>::new();
/// let json_writer = SimpleJsonWriter::new(&mut writer);
/// json_writer.write_object(|object_writer| {
/// object_writer.write_number_member("a", 1)?;
/// object_writer.write_bool_member("b", true)?;
/// Ok(())
/// })?;
///
/// let json = String::from_utf8(writer)?;
/// assert_eq!(json, r#"{"a":1,"b":true}"#);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
fn write_object(
self,
f: impl FnOnce(&mut ObjectWriter<'_, J>) -> Result<(), Box<dyn Error>>,
) -> Result<(), Box<dyn Error>>;
}
fn write_array<J: JsonWriter>(
json_writer: &mut ErrorSafeJsonWriter<J>,
f: impl FnOnce(&mut ArrayWriter<'_, J>) -> Result<(), Box<dyn Error>>,
) -> Result<(), Box<dyn Error>> {
json_writer.begin_array()?;
let mut array_writer = ArrayWriter { json_writer };
f(&mut array_writer)?;
json_writer.end_array()?;
Ok(())
}
fn write_object<J: JsonWriter>(
json_writer: &mut ErrorSafeJsonWriter<J>,
f: impl FnOnce(&mut ObjectWriter<'_, J>) -> Result<(), Box<dyn Error>>,
) -> Result<(), Box<dyn Error>> {
json_writer.begin_object()?;
let mut object_writer = ObjectWriter { json_writer };
f(&mut object_writer)?;
json_writer.end_object()?;
Ok(())
}
fn write_string_with_writer<J: JsonWriter>(
json_writer: &mut ErrorSafeJsonWriter<J>,
f: impl FnOnce(StringValueWriter<'_>) -> Result<(), Box<dyn Error>>,
) -> Result<(), Box<dyn Error>> {
let mut delegate = json_writer.string_value_writer()?;
let string_writer = StringValueWriter {
delegate: &mut delegate as &mut dyn AdvancedStringValueWriter,
};
f(string_writer)?;
// Check if there is error which was not propagated by function
if let Some(error) = delegate.error {
return Err(error_from_stored(error).into());
}
delegate.finish_value()?;
Ok(())
}
mod error_safe_writer {
use std::io::ErrorKind;
use super::*;
use crate::writer::IoError;
pub(super) type StoredIoError = (ErrorKind, String);
pub(super) fn convert_io_error(error: &IoError) -> StoredIoError {
(error.kind(), error.to_string())
}
fn convert_number_error(error: &JsonNumberError) -> StoredIoError {
match error {
JsonNumberError::InvalidNumber(message) => (ErrorKind::Other, message.clone()),
JsonNumberError::IoError(e) => convert_io_error(e),
}
}
pub(super) fn error_from_stored(error: &StoredIoError) -> IoError {
// Report as `Other` kind (and with custom message) to avoid caller indefinitely retrying
// because it considers the original error kind as safe to retry
// And also because the original error might have been related to originally provided data
// (e.g. invalid UTF-8 data) and is unrelated to the now called JSON writer method
IoError::other(format!("previous error '{}': {}", error.0, error.1.clone()))
}
/// If previously an error had occurred, returns that error. Otherwise uses the delegate
/// writer and in case of an error stores it to prevent subsequent usage.
/* This is a macro instead of a function to support error conversion */
macro_rules! use_delegate {
($self:ident, |$json_writer:ident| $writing_action:expr, |$original_error:ident| $original_error_converter:expr, |$stored_error:ident| $stored_error_converter:expr) => {
if let Some(error) = &$self.error {
let $stored_error = error_from_stored(error);
Err($stored_error_converter)
} else {
let $json_writer = &mut $self.delegate;
let result = $writing_action;
if let Err($original_error) = &result {
$self.error = Some($original_error_converter);
}
result
}
};
($self:ident, |$json_writer:ident| $writing_action:expr) => {
use_delegate!(
$self,
|$json_writer| $writing_action,
|original_error| convert_io_error(original_error),
|stored_error| stored_error
)
};
}
/// [`JsonWriter`] implementation which in case of errors keeps returning the error and does
/// not use the underlying JSON writer anymore
///
/// This is mainly to protect against user-provided closures or functions which accidentally
/// discard and not propagate writer errors, which could lead to subsequent panics. How exactly
/// this writer repeats errors or what information it preserves is unspecified; users should
/// always propagate writer errors and not (intentionally) rely on this safeguard here.
#[derive(Debug)]
pub(super) struct ErrorSafeJsonWriter<J: JsonWriter> {
pub(super) delegate: J,
// Store as `IoError` (destructured as `(kind, message)`) because that is the common error type
// supported by all methods
pub(super) error: Option<StoredIoError>,
}
impl<J: JsonWriter> JsonWriter for ErrorSafeJsonWriter<J> {
fn begin_object(&mut self) -> Result<(), IoError> {
use_delegate!(self, |w| w.begin_object())
}
fn end_object(&mut self) -> Result<(), IoError> {
use_delegate!(self, |w| w.end_object())
}
fn begin_array(&mut self) -> Result<(), IoError> {
use_delegate!(self, |w| w.begin_array())
}
fn end_array(&mut self) -> Result<(), IoError> {
use_delegate!(self, |w| w.end_array())
}
fn name(&mut self, name: &str) -> Result<(), IoError> {
use_delegate!(self, |w| w.name(name))
}
fn null_value(&mut self) -> Result<(), IoError> {
use_delegate!(self, |w| w.null_value())
}
fn bool_value(&mut self, value: bool) -> Result<(), IoError> {
use_delegate!(self, |w| w.bool_value(value))
}
fn string_value(&mut self, value: &str) -> Result<(), IoError> {
use_delegate!(self, |w| w.string_value(value))
}
fn string_value_writer(
&mut self,
) -> Result<ErrorSafeStringValueWriter<'_, impl AdvancedStringValueWriter>, IoError>
{
let string_writer_delegate = use_delegate!(self, |w| w.string_value_writer())?;
Ok(ErrorSafeStringValueWriter {
delegate: string_writer_delegate,
// Store errors in the `error` field of this `ErrorSafeStringValueWriter`, so they are
// available to the original JsonWriter afterwards
error: &mut self.error,
})
}
fn number_value_from_string(&mut self, value: &str) -> Result<(), JsonNumberError> {
use_delegate!(
self,
|w| w.number_value_from_string(value),
|original_error| convert_number_error(original_error),
|stored_error| JsonNumberError::IoError(stored_error)
)
}
fn number_value<N: FiniteNumber>(&mut self, value: N) -> Result<(), IoError> {
use_delegate!(self, |w| w.number_value(value))
}
fn fp_number_value<N: FloatingPointNumber>(
&mut self,
value: N,
) -> Result<(), JsonNumberError> {
use_delegate!(
self,
|w| w.fp_number_value(value),
|original_error| convert_number_error(original_error),
|stored_error| JsonNumberError::IoError(stored_error)
)
}
#[cfg(feature = "serde")]
fn serialize_value<S: serde::ser::Serialize>(
&mut self,
value: &S,
) -> Result<(), crate::serde::SerializerError> {
use crate::serde::SerializerError;
use_delegate!(
self,
|w| w.serialize_value(value),
|original_error| match original_error {
SerializerError::IoError(e) => convert_io_error(e),
e => (ErrorKind::Other, e.to_string()),
},
// Note: Could also create `SerializerError::Custom` instead
|stored_error| SerializerError::IoError(stored_error)
)
}
fn finish_document(self) -> Result<(), IoError> {
// Special code because this method consumes `self`
if let Some(error) = self.error {
return Err(error_from_stored(&error));
}
self.delegate.finish_document()
}
}
// Note: Repeating errors here might be a bit redundant if JsonStreamWriter is used since it does
// this itself as well; but that is not guaranteed for all JsonWriter implementations
pub(super) struct ErrorSafeStringValueWriter<'a, D: AdvancedStringValueWriter> {
delegate: D,
pub(super) error: &'a mut Option<StoredIoError>,
}
impl<D: AdvancedStringValueWriter> ErrorSafeStringValueWriter<'_, D> {
fn use_delegate<T>(
&mut self,
f: impl FnOnce(&mut D) -> std::io::Result<T>,
) -> std::io::Result<T> {
if let Some(error) = self.error {
return Err(error_from_stored(error));
}
let result = f(&mut self.delegate);
if let Err(error) = &result {
*self.error = Some(convert_io_error(error));
}
result
}
}
impl<D: AdvancedStringValueWriter> Write for ErrorSafeStringValueWriter<'_, D> {
fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
self.use_delegate(|d| d.write(buf))
}
fn flush(&mut self) -> std::io::Result<()> {
self.use_delegate(|d| d.flush())
}
}
impl<D: AdvancedStringValueWriter> AdvancedStringValueWriter for ErrorSafeStringValueWriter<'_, D> {
fn write_str(&mut self, s: &str) -> Result<(), IoError> {
self.use_delegate(|d| d.write_str(s))
}
fn finish_value(self) -> Result<(), IoError> {
// Special code because this method consumes `self`
if let Some(error) = self.error {
return Err(error_from_stored(error));
}
let result = self.delegate.finish_value();
if let Err(error) = &result {
*self.error = Some(convert_io_error(error));
}
result
}
}
}
/// JSON writer variant which is easier to use than [`JsonWriter`]
///
/// This JSON writer variant ensures correct usage at compile-time making it easier and less
/// error-prone to use than [`JsonWriter`], which validates correct usage at runtime and panics
/// on incorrect usage. However, this comes at the cost of `SimpleJsonWriter` being less flexible
/// to use, and it not offerring all features of [`JsonWriter`].
///
/// When an error is returned by one of the methods of the writer, the error should be propagated
/// (for example by using Rust's `?` operator), processing should be aborted and the writer should
/// not be used any further.
///
/// # Examples
/// ```
/// # use struson::writer::simple::*;
/// // In this example JSON bytes are stored in a Vec;
/// // normally they would be written to a file or network connection
/// let mut writer = Vec::<u8>::new();
/// let json_writer = SimpleJsonWriter::new(&mut writer);
/// json_writer.write_object(|object_writer| {
/// object_writer.write_number_member("a", 1)?;
/// object_writer.write_bool_member("b", true)?;
/// Ok(())
/// })?;
///
/// let json = String::from_utf8(writer)?;
/// assert_eq!(json, r#"{"a":1,"b":true}"#);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[derive(Debug)]
pub struct SimpleJsonWriter<J: JsonWriter> {
json_writer: ErrorSafeJsonWriter<J>,
}
impl<J: JsonWriter> SimpleJsonWriter<J> {
/// Creates a new `SimpleJsonWriter` from the given [`JsonWriter`]
///
/// The `JsonWriter` acts as delegate which performs the actual JSON writing. It should
/// not have written any JSON data yet, otherwise the behavior of the created `SimpleJsonWriter`
/// is unspecified and it may panic.
///
/// # Examples
/// ```
/// # use struson::writer::*;
/// # use struson::writer::simple::*;
/// let mut writer = Vec::<u8>::new();
/// # #[allow(unused_variables)]
/// let json_writer = SimpleJsonWriter::from_json_writer(
/// JsonStreamWriter::new_custom(
/// &mut writer,
/// WriterSettings {
/// pretty_print: true,
/// // For all other settings use the default
/// ..Default::default()
/// },
/// )
/// );
/// ```
pub fn from_json_writer(json_writer: J) -> Self {
SimpleJsonWriter {
json_writer: ErrorSafeJsonWriter {
delegate: json_writer,
error: None,
},
}
}
}
impl<W: Write> SimpleJsonWriter<JsonStreamWriter<W>> {
/// Creates a new JSON writer
///
/// The JSON data will be written UTF-8 encoded to the writer. Internally this creates a [`JsonStreamWriter`]
/// which acts as delegate; see its documentation for more information about the writing behavior.
pub fn new(writer: W) -> Self {
SimpleJsonWriter::from_json_writer(JsonStreamWriter::new(writer))
}
}
// These methods all call `json_writer.finish_document()` because `SimpleJsonWriter`
// is intended to be used for top-level value
impl<J: JsonWriter> ValueWriter<J> for SimpleJsonWriter<J> {
fn write_null(mut self) -> Result<(), IoError> {
self.json_writer.null_value()?;
self.json_writer.finish_document()
}
fn write_bool(mut self, value: bool) -> Result<(), IoError> {
self.json_writer.bool_value(value)?;
self.json_writer.finish_document()
}
fn write_string(mut self, value: &str) -> Result<(), IoError> {
self.json_writer.string_value(value)?;
self.json_writer.finish_document()
}
fn write_string_with_writer(
mut self,
f: impl FnOnce(StringValueWriter<'_>) -> Result<(), Box<dyn Error>>,
) -> Result<(), Box<dyn Error>> {
write_string_with_writer(&mut self.json_writer, f)?;
self.json_writer.finish_document()?;
Ok(())
}
fn write_number<N: FiniteNumber>(mut self, value: N) -> Result<(), IoError> {
self.json_writer.number_value(value)?;
self.json_writer.finish_document()
}
fn write_fp_number<N: FloatingPointNumber>(mut self, value: N) -> Result<(), JsonNumberError> {
self.json_writer.fp_number_value(value)?;
// Using `?` here is a bit misleading since that will wrap an IO error from `finish_document()`
// in a `JsonNumberError`, but that is probably acceptable
self.json_writer.finish_document()?;
Ok(())
}
fn write_number_string(mut self, value: &str) -> Result<(), JsonNumberError> {
self.json_writer.number_value_from_string(value)?;
// Using `?` here is a bit misleading since that will wrap an IO error from `finish_document()`
// in a `JsonNumberError`, but that is probably acceptable
self.json_writer.finish_document()?;
Ok(())
}
#[cfg(feature = "serde")]
fn write_serialize<S: serde::ser::Serialize>(
mut self,
value: &S,
) -> Result<(), crate::serde::SerializerError> {
self.json_writer.serialize_value(value)?;
// Using `?` here is a bit misleading since that will wrap an IO error from `finish_document()`
// in a `SerializerError`, but that is probably acceptable
self.json_writer.finish_document()?;
Ok(())
}
fn write_array(
mut self,
f: impl FnOnce(&mut ArrayWriter<'_, J>) -> Result<(), Box<dyn Error>>,
) -> Result<(), Box<dyn Error>> {
write_array(&mut self.json_writer, f)?;
self.json_writer.finish_document()?;
Ok(())
}
fn write_object(
mut self,
f: impl FnOnce(&mut ObjectWriter<'_, J>) -> Result<(), Box<dyn Error>>,
) -> Result<(), Box<dyn Error>> {
write_object(&mut self.json_writer, f)?;
self.json_writer.finish_document()?;
Ok(())
}
}
/// Writer for JSON array items
///
/// This struct is used by [`ValueWriter::write_array`].
#[derive(Debug)]
pub struct ArrayWriter<'a, J: JsonWriter> {
json_writer: &'a mut ErrorSafeJsonWriter<J>,
}
// Implement for `&mut ArrayWriter` to allow writing multiple values instead of just one
impl<J: JsonWriter> ValueWriter<J> for &mut ArrayWriter<'_, J> {
fn write_null(self) -> Result<(), IoError> {
self.json_writer.null_value()
}
fn write_bool(self, value: bool) -> Result<(), IoError> {
self.json_writer.bool_value(value)
}
fn write_string(self, value: &str) -> Result<(), IoError> {
self.json_writer.string_value(value)
}
fn write_string_with_writer(
self,
f: impl FnOnce(StringValueWriter<'_>) -> Result<(), Box<dyn Error>>,
) -> Result<(), Box<dyn Error>> {
write_string_with_writer(self.json_writer, f)
}
fn write_number<N: FiniteNumber>(self, value: N) -> Result<(), IoError> {
self.json_writer.number_value(value)
}
fn write_fp_number<N: FloatingPointNumber>(self, value: N) -> Result<(), JsonNumberError> {
self.json_writer.fp_number_value(value)?;
Ok(())
}
fn write_number_string(self, value: &str) -> Result<(), JsonNumberError> {
self.json_writer.number_value_from_string(value)?;
Ok(())
}
#[cfg(feature = "serde")]
fn write_serialize<S: serde::ser::Serialize>(
self,
value: &S,
) -> Result<(), crate::serde::SerializerError> {
self.json_writer.serialize_value(value)?;
Ok(())
}
fn write_array(
self,
f: impl FnOnce(&mut ArrayWriter<'_, J>) -> Result<(), Box<dyn Error>>,
) -> Result<(), Box<dyn Error>> {
write_array(self.json_writer, f)
}
fn write_object(
self,
f: impl FnOnce(&mut ObjectWriter<'_, J>) -> Result<(), Box<dyn Error>>,
) -> Result<(), Box<dyn Error>> {
write_object(self.json_writer, f)
}
}
/// Writer for JSON object members
///
/// Each method writes a JSON object member in the form of a name-value pair.
/// For example the member `"a": 1` consists of the name "a" and the value 1,
/// which can be written using [`write_number_member`](Self::write_number_member).
///
/// The methods of this trait are similar to the methods of [`ValueWriter`], see its
/// documentation for more details on how the JSON values are written.
///
/// This struct is used by [`ValueWriter::write_object`].
#[derive(Debug)]
pub struct ObjectWriter<'a, J: JsonWriter> {
json_writer: &'a mut ErrorSafeJsonWriter<J>,
}
impl<J: JsonWriter> ObjectWriter<'_, J> {
/// Writes a member with JSON null as value
pub fn write_null_member(&mut self, name: &str) -> Result<(), IoError> {
self.json_writer.name(name)?;
self.json_writer.null_value()
}
/// Writes a member with a JSON boolean as value
pub fn write_bool_member(&mut self, name: &str, value: bool) -> Result<(), IoError> {
self.json_writer.name(name)?;
self.json_writer.bool_value(value)
}
/// Writes a member with a JSON string as value
pub fn write_string_member(&mut self, name: &str, value: &str) -> Result<(), IoError> {
self.json_writer.name(name)?;
self.json_writer.string_value(value)
}
/// Writes a member with a JSON string as value, using a [`Write`]
pub fn write_string_member_with_writer(
&mut self,
name: &str,
f: impl FnOnce(StringValueWriter<'_>) -> Result<(), Box<dyn Error>>,
) -> Result<(), Box<dyn Error>> {
self.json_writer.name(name)?;
write_string_with_writer(self.json_writer, f)
}
/// Writes a member with a JSON number as value
pub fn write_number_member<N: FiniteNumber>(
&mut self,
name: &str,
value: N,
) -> Result<(), IoError> {
self.json_writer.name(name)?;
self.json_writer.number_value(value)
}
/// Writes a member with a floating point JSON number as value
///
/// Returns an error if the number is non-finite and therefore cannot be written
/// as JSON number value.
pub fn write_fp_number_member<N: FloatingPointNumber>(
&mut self,
name: &str,
value: N,
) -> Result<(), JsonNumberError> {
self.json_writer.name(name)?;
self.json_writer.fp_number_value(value)
}
/// Writes a member with the string representation of a JSON number as value
///
/// Returns an error if the string is not a valid JSON number value.
pub fn write_number_string_member(
&mut self,
name: &str,
value: &str,
) -> Result<(), JsonNumberError> {
self.json_writer.name(name)?;
self.json_writer.number_value_from_string(value)
}
/// Writes a member with a Serde [`Serialize`](serde::ser::Serialize) as value
///
/// This method is part of the optional Serde integration feature, see the
/// [`serde` module](crate::serde) of this crate for more information.
/*
* This is called 'serialize*d*' because 'serialize_member' might be a bit misleading since
* it is not serializing the whole member but only the member value
*/
#[cfg(feature = "serde")]
pub fn write_serialized_member<S: serde::ser::Serialize>(
&mut self,
name: &str,
value: &S,
) -> Result<(), crate::serde::SerializerError> {
self.json_writer.name(name)?;
self.json_writer.serialize_value(value)
}
/// Writes a member with a JSON array as value
pub fn write_array_member(
&mut self,
name: &str,
f: impl FnOnce(&mut ArrayWriter<'_, J>) -> Result<(), Box<dyn Error>>,
) -> Result<(), Box<dyn Error>> {
self.json_writer.name(name)?;
write_array(self.json_writer, f)
}
/// Writes a member with a JSON object as value
pub fn write_object_member(
&mut self,
name: &str,
f: impl FnOnce(&mut ObjectWriter<'_, J>) -> Result<(), Box<dyn Error>>,
) -> Result<(), Box<dyn Error>> {
self.json_writer.name(name)?;
write_object(self.json_writer, f)
}
}
/// Writer for a JSON string value
///
/// Characters are automatically escaped in the JSON output if necessary. Writing invalid
/// UTF-8 data will cause a [`std::io::Error`].
///
/// This struct is used by [`ValueWriter::write_string_with_writer`].
///
/// # Error behavior
/// The error behavior of this string writer differs from the guarantees made by [`Write`]:
/// - if an error is returned there are no guarantees about if or how many bytes have been
/// written
/// - if an error occurs, processing should be aborted, regardless of the kind of the error;
/// trying to use this string writer or the original JSON writer afterwards will lead
/// to unspecified behavior
/* TODO: Should implement `Debug`, but seems to not be easily possible when using `dyn` below */
pub struct StringValueWriter<'a> {
// TODO: Ideally would avoid `dyn` here, but using generic type parameter seems to not be
// easily possible when `JsonWriter::string_value_writer()` does not use associated type
// and `FnOnce` cannot use `impl Trait` for arguments
delegate: &'a mut dyn AdvancedStringValueWriter,
}
impl Write for StringValueWriter<'_> {
fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
self.delegate.write(buf)
}
fn flush(&mut self) -> std::io::Result<()> {
self.delegate.flush()
}
}
impl StringValueWriter<'_> {
/// Writes a string value piece
///
/// This method behaves the same way as if all the string bytes were written using
/// the `write` method, however this method might be more efficient. Therefore if
/// a value already exists as string, using `write_str` is likely at least as
/// efficient as using the `write` method.
///
/// Calls to `write_str` can be mixed with regular `write` calls, however preceding
/// `write` calls must have written complete UTF-8 data, otherwise an error is returned.
pub fn write_str(&mut self, s: &str) -> Result<(), IoError> {
self.delegate.write_str(s)
}
}