binrw 0.10.0

// Lint: This code is mostly taken from `std::io` which does not use the
// pedantic lint group.
#![allow(clippy::pedantic)]

mod cursor;
mod error;

use alloc::{string::String, vec::Vec};
use core::{cmp, fmt, mem};
pub use {
    cursor::Cursor,
    error::{Error, ErrorKind},
};

/// A specialized [`Result`] type for I/O operations.
pub type Result<T> = core::result::Result<T, Error>;

/// The `Read` trait allows for reading bytes from a source.
pub trait Read {
    /// Pull some bytes from this source into the specified buffer, returning
    /// how many bytes were read.
    fn read(&mut self, buf: &mut [u8]) -> Result<usize>;

    /// Read the exact number of bytes required to fill `buf`.
    fn read_exact(&mut self, mut buf: &mut [u8]) -> Result<()> {
        while !buf.is_empty() {
            match self.read(buf) {
                Ok(0) => break,
                Ok(n) => {
                    let tmp = buf;
                    buf = &mut tmp[n..];
                }
                Err(ref e) if e.kind() == ErrorKind::Interrupted => {}
                Err(e) => return Err(e),
            }
        }
        if !buf.is_empty() {
            Err(Error::new(
                ErrorKind::UnexpectedEof,
                "failed to fill whole buffer",
            ))
        } else {
            Ok(())
        }
    }

    /// Read all bytes until EOF in this source, placing them into `buf`.
    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize> {
        let mut tmp = [0; 32];
        let mut amt = 0;

        loop {
            match self.read(&mut tmp) {
                Ok(0) => break Ok(amt),
                Ok(n) => {
                    amt += n;
                    buf.extend_from_slice(&tmp[..n]);
                }
                Err(err) if err.kind() == ErrorKind::Interrupted => continue,
                err @ Err(_) => return err,
            }
        }
    }

    /// Read all bytes until EOF in this source, appending them to `buf`.
    fn read_to_string(&mut self, buf: &mut String) -> Result<usize> {
        let mut tmp = Vec::new();
        let amt = self.read_to_end(&mut tmp)?;
        let str = core::str::from_utf8(&tmp).map_err(|_| {
            Error::new(ErrorKind::InvalidData, "stream did not contain valid UTF-8")
        })?;
        buf.push_str(str);
        Ok(amt)
    }

    /// Transforms this `Read` instance to an [`Iterator`] over its bytes.
    fn bytes(self) -> Bytes<Self>
    where
        Self: Sized,
    {
        Bytes { inner: self }
    }

    /// Creates a "by reference" adaptor for this instance of `Read`.
    fn by_ref(&mut self) -> &mut Self
    where
        Self: Sized,
    {
        self
    }

    /// Creates an adaptor which will read at most `limit` bytes from it.
    fn take(self, limit: u64) -> Take<Self>
    where
        Self: Sized,
    {
        Take { inner: self, limit }
    }
}

/// Reader adaptor which limits the bytes read from an underlying reader.
///
/// This struct is generally created by calling [`take`] on a reader.
/// Please see the documentation of [`take`] for more details.
///
/// [`take`]: Read::take
#[derive(Debug)]
pub struct Take<T> {
    inner: T,
    limit: u64,
}

impl<T> Take<T> {
    /// Returns the number of bytes that can be read before this instance will
    /// return EOF.
    pub fn limit(&self) -> u64 {
        self.limit
    }

    /// Sets the number of bytes that can be read before this instance will
    /// return EOF. This is the same as constructing a new `Take` instance, so
    /// the amount of bytes read and the previous limit value don't matter when
    /// calling this method.
    pub fn set_limit(&mut self, limit: u64) {
        self.limit = limit;
    }

    /// Consumes the `Take`, returning the wrapped reader.
    pub fn into_inner(self) -> T {
        self.inner
    }

    /// Gets a reference to the underlying reader.
    pub fn get_ref(&self) -> &T {
        &self.inner
    }

    /// Gets a mutable reference to the underlying reader.
    pub fn get_mut(&mut self) -> &mut T {
        &mut self.inner
    }
}

impl<T: Read> Read for Take<T> {
    fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
        // Don't call into inner reader at all at EOF because it may still block
        if self.limit == 0 {
            return Ok(0);
        }

        let max = core::cmp::min(buf.len() as u64, self.limit) as usize;
        let n = self.inner.read(&mut buf[..max])?;
        self.limit -= n as u64;
        Ok(n)
    }
}

impl<R: Read + ?Sized> Read for &mut R {
    #[inline]
    fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
        (**self).read(buf)
    }

    #[inline]
    fn read_exact(&mut self, buf: &mut [u8]) -> Result<()> {
        (**self).read_exact(buf)
    }
}

/// An iterator over `u8` values of a reader.
#[derive(Debug)]
pub struct Bytes<R: Read> {
    inner: R,
}

impl<R: Read> Iterator for Bytes<R> {
    type Item = Result<u8>;

    fn next(&mut self) -> Option<Result<u8>> {
        let mut byte = 0;
        loop {
            return match self.inner.read(core::slice::from_mut(&mut byte)) {
                Ok(0) => None,
                Ok(..) => Some(Ok(byte)),
                Err(ref e) if e.kind() == ErrorKind::Interrupted => continue,
                Err(e) => Some(Err(e)),
            };
        }
    }
}

impl Read for &[u8] {
    #[inline]
    fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
        let amt = cmp::min(buf.len(), self.len());
        let (a, b) = self.split_at(amt);

        // First check if the amount of bytes we want to read is small:
        // `copy_from_slice` will generally expand to a call to `memcpy`, and
        // for a single byte the overhead is significant.
        if amt == 1 {
            buf[0] = a[0];
        } else {
            buf[..amt].copy_from_slice(a);
        }

        *self = b;
        Ok(amt)
    }

    #[inline]
    fn read_exact(&mut self, buf: &mut [u8]) -> Result<()> {
        if buf.len() > self.len() {
            return Err(Error::new(
                ErrorKind::UnexpectedEof,
                "failed to fill whole buffer",
            ));
        }
        let (a, b) = self.split_at(buf.len());

        // First check if the amount of bytes we want to read is small:
        // `copy_from_slice` will generally expand to a call to `memcpy`, and
        // for a single byte the overhead is significant.
        if buf.len() == 1 {
            buf[0] = a[0];
        } else {
            buf.copy_from_slice(a);
        }

        *self = b;
        Ok(())
    }

    #[inline]
    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize> {
        buf.extend_from_slice(self);
        let len = self.len();
        *self = &self[len..];
        Ok(len)
    }
}

/// Enumeration of possible methods to seek within an I/O object.
#[derive(Debug, Clone, Copy)]
pub enum SeekFrom {
    /// Sets the offset to the provided number of bytes.
    Start(u64),
    /// Sets the offset to the size of this object plus the specified number of
    /// bytes.
    End(i64),
    /// Sets the offset to the current position plus the specified number of
    /// bytes.
    Current(i64),
}

/// The `Seek` trait provides a cursor which can be moved within a stream of
/// bytes.
pub trait Seek {
    /// Seek to an offset, in bytes, in a stream.
    fn seek(&mut self, pos: SeekFrom) -> Result<u64>;
    /// Returns the current seek position from the start of the stream.
    ///
    /// This is equivalent to `self.seek(SeekFrom::Current(0))`.
    fn stream_position(&mut self) -> Result<u64> {
        self.seek(SeekFrom::Current(0))
    }
}

impl<S: Seek + ?Sized> Seek for &mut S {
    #[inline]
    fn seek(&mut self, pos: SeekFrom) -> Result<u64> {
        (**self).seek(pos)
    }
}

/// A trait for objects which are byte-oriented sinks.
pub trait Write {
    /// Write a buffer into this writer, returning how many bytes were written.
    fn write(&mut self, buf: &[u8]) -> Result<usize>;

    /// Flush this output stream, ensuring that all intermediately buffered
    /// contents reach their destination.
    fn flush(&mut self) -> Result<()>;

    /// Attempts to write an entire buffer into this writer.
    fn write_all(&mut self, mut buf: &[u8]) -> Result<()> {
        while !buf.is_empty() {
            match self.write(buf) {
                Ok(0) => {
                    return Err(Error::new(
                        ErrorKind::WriteZero,
                        "failed to write whole buffer",
                    ));
                }
                Ok(n) => buf = &buf[n..],
                Err(ref e) if e.kind() == ErrorKind::Interrupted => {}
                Err(e) => return Err(e),
            }
        }
        Ok(())
    }

    /// Writes a formatted string into this writer, returning any error
    /// encountered.
    fn write_fmt(&mut self, fmt: fmt::Arguments<'_>) -> Result<()> {
        // Create a shim which translates a Write to a fmt::Write and saves
        // off I/O errors. instead of discarding them
        struct Adaptor<'a, T: ?Sized> {
            inner: &'a mut T,
            error: Result<()>,
        }

        impl<T: Write + ?Sized> fmt::Write for Adaptor<'_, T> {
            fn write_str(&mut self, s: &str) -> fmt::Result {
                match self.inner.write_all(s.as_bytes()) {
                    Ok(()) => Ok(()),
                    Err(e) => {
                        self.error = Err(e);
                        Err(fmt::Error)
                    }
                }
            }
        }

        let mut output = Adaptor {
            inner: self,
            error: Ok(()),
        };
        match fmt::write(&mut output, fmt) {
            Ok(()) => Ok(()),
            Err(..) => {
                // check if the error came from the underlying `Write` or not
                if output.error.is_err() {
                    output.error
                } else {
                    Err(Error::new(ErrorKind::Other, "formatter error"))
                }
            }
        }
    }

    /// Creates a "by reference" adaptor for this instance of `Write`.
    fn by_ref(&mut self) -> &mut Self
    where
        Self: Sized,
    {
        self
    }
}

impl Write for &mut [u8] {
    #[inline]
    fn write(&mut self, data: &[u8]) -> Result<usize> {
        let amt = cmp::min(data.len(), self.len());
        let (a, b) = mem::take(self).split_at_mut(amt);
        a.copy_from_slice(&data[..amt]);
        *self = b;
        Ok(amt)
    }

    #[inline]
    fn write_all(&mut self, data: &[u8]) -> Result<()> {
        if self.write(data)? == data.len() {
            Ok(())
        } else {
            Err(Error::new(
                ErrorKind::WriteZero,
                &"failed to write whole buffer",
            ))
        }
    }

    #[inline]
    fn flush(&mut self) -> Result<()> {
        Ok(())
    }
}

impl Write for Vec<u8> {
    #[inline]
    fn write(&mut self, buf: &[u8]) -> Result<usize> {
        self.extend_from_slice(buf);
        Ok(buf.len())
    }

    #[inline]
    fn write_all(&mut self, buf: &[u8]) -> Result<()> {
        self.extend_from_slice(buf);
        Ok(())
    }

    #[inline]
    fn flush(&mut self) -> Result<()> {
        Ok(())
    }
}