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use alloc::vec::Vec;
#[cfg(feature = "std")]
use std::{io, mem};
use crate::pod::{bytes_of, bytes_of_slice, Pod};
/// Trait for writable buffer.
#[allow(clippy::len_without_is_empty)]
pub trait WritableBuffer {
/// Returns position/offset for data to be written at.
///
/// Should only be used in debug assertions
fn len(&self) -> usize;
/// Reserves specified number of bytes in the buffer.
///
/// This will be called exactly once before writing anything to the buffer,
/// and the given size is the exact total number of bytes that will be written.
fn reserve(&mut self, size: usize) -> Result<(), ()>;
/// Writes zero bytes at the end of the buffer until the buffer
/// has the specified length.
fn resize(&mut self, new_len: usize);
/// Writes the specified slice of bytes at the end of the buffer.
fn write_bytes(&mut self, val: &[u8]);
/// Writes the specified `Pod` type at the end of the buffer.
fn write_pod<T: Pod>(&mut self, val: &T)
where
Self: Sized,
{
self.write_bytes(bytes_of(val))
}
/// Writes the specified `Pod` slice at the end of the buffer.
fn write_pod_slice<T: Pod>(&mut self, val: &[T])
where
Self: Sized,
{
self.write_bytes(bytes_of_slice(val))
}
}
impl<'a> dyn WritableBuffer + 'a {
/// Writes the specified `Pod` type at the end of the buffer.
pub fn write<T: Pod>(&mut self, val: &T) {
self.write_bytes(bytes_of(val))
}
/// Writes the specified `Pod` slice at the end of the buffer.
pub fn write_slice<T: Pod>(&mut self, val: &[T]) {
self.write_bytes(bytes_of_slice(val))
}
}
impl WritableBuffer for Vec<u8> {
#[inline]
fn len(&self) -> usize {
self.len()
}
#[inline]
fn reserve(&mut self, size: usize) -> Result<(), ()> {
debug_assert!(self.is_empty());
self.reserve(size);
Ok(())
}
#[inline]
fn resize(&mut self, new_len: usize) {
debug_assert!(new_len >= self.len());
self.resize(new_len, 0);
}
#[inline]
fn write_bytes(&mut self, val: &[u8]) {
debug_assert!(self.len() + val.len() <= self.capacity());
self.extend_from_slice(val)
}
}
/// A [`WritableBuffer`] that streams data to a [`Write`](std::io::Write) implementation.
///
/// [`Self::result`] must be called to determine if an I/O error occurred during writing.
///
/// It is advisable to use a buffered writer like [`BufWriter`](std::io::BufWriter)
/// instead of an unbuffered writer like [`File`](std::fs::File).
#[cfg(feature = "std")]
#[derive(Debug)]
pub struct StreamingBuffer<W> {
writer: W,
len: usize,
result: Result<(), io::Error>,
}
#[cfg(feature = "std")]
impl<W> StreamingBuffer<W> {
/// Create a new `StreamingBuffer` backed by the given writer.
pub fn new(writer: W) -> Self {
StreamingBuffer {
writer,
len: 0,
result: Ok(()),
}
}
/// Unwraps this [`StreamingBuffer`] giving back the original writer.
pub fn into_inner(self) -> W {
self.writer
}
/// Returns any error that occurred during writing.
pub fn result(&mut self) -> Result<(), io::Error> {
mem::replace(&mut self.result, Ok(()))
}
}
#[cfg(feature = "std")]
impl<W: io::Write> WritableBuffer for StreamingBuffer<W> {
#[inline]
fn len(&self) -> usize {
self.len
}
#[inline]
fn reserve(&mut self, _size: usize) -> Result<(), ()> {
Ok(())
}
#[inline]
fn resize(&mut self, new_len: usize) {
debug_assert!(self.len <= new_len);
while self.len < new_len {
let write_amt = (new_len - self.len - 1) % 1024 + 1;
self.write_bytes(&[0; 1024][..write_amt]);
}
}
#[inline]
fn write_bytes(&mut self, val: &[u8]) {
if self.result.is_ok() {
self.result = self.writer.write_all(val);
}
self.len += val.len();
}
}
/// A trait for mutable byte slices.
///
/// It provides convenience methods for `Pod` types.
pub(crate) trait BytesMut {
fn write_at<T: Pod>(self, offset: usize, val: &T) -> Result<(), ()>;
}
impl<'a> BytesMut for &'a mut [u8] {
#[inline]
fn write_at<T: Pod>(self, offset: usize, val: &T) -> Result<(), ()> {
let src = bytes_of(val);
let dest = self.get_mut(offset..).ok_or(())?;
let dest = dest.get_mut(..src.len()).ok_or(())?;
dest.copy_from_slice(src);
Ok(())
}
}
/// Write an unsigned number using the LEB128 encoding to a buffer.
///
/// Returns the number of bytes written.
#[allow(dead_code)]
pub(crate) fn write_uleb128(buf: &mut Vec<u8>, mut val: u64) -> usize {
let mut len = 0;
loop {
let mut byte = (val & 0x7f) as u8;
val >>= 7;
let done = val == 0;
if !done {
byte |= 0x80;
}
buf.push(byte);
len += 1;
if done {
return len;
}
}
}
/// Write a signed number using the LEB128 encoding to a buffer.
///
/// Returns the number of bytes written.
#[allow(dead_code)]
pub(crate) fn write_sleb128(buf: &mut Vec<u8>, mut val: i64) -> usize {
let mut len = 0;
loop {
let mut byte = val as u8;
// Keep the sign bit for testing
val >>= 6;
let done = val == 0 || val == -1;
if done {
byte &= !0x80;
} else {
// Remove the sign bit
val >>= 1;
byte |= 0x80;
}
buf.push(byte);
len += 1;
if done {
return len;
}
}
}
pub(crate) fn align(offset: usize, size: usize) -> usize {
(offset + (size - 1)) & !(size - 1)
}
#[allow(dead_code)]
pub(crate) fn align_u32(offset: u32, size: u32) -> u32 {
(offset + (size - 1)) & !(size - 1)
}
#[allow(dead_code)]
pub(crate) fn align_u64(offset: u64, size: u64) -> u64 {
(offset + (size - 1)) & !(size - 1)
}
pub(crate) fn write_align(buffer: &mut dyn WritableBuffer, size: usize) {
let new_len = align(buffer.len(), size);
buffer.resize(new_len);
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn bytes_mut() {
let data = vec![0x01, 0x23, 0x45, 0x67];
let mut bytes = data.clone();
bytes.extend_from_slice(bytes_of(&u16::to_be(0x89ab)));
assert_eq!(bytes, [0x01, 0x23, 0x45, 0x67, 0x89, 0xab]);
let mut bytes = data.clone();
assert_eq!(bytes.write_at(0, &u16::to_be(0x89ab)), Ok(()));
assert_eq!(bytes, [0x89, 0xab, 0x45, 0x67]);
let mut bytes = data.clone();
assert_eq!(bytes.write_at(2, &u16::to_be(0x89ab)), Ok(()));
assert_eq!(bytes, [0x01, 0x23, 0x89, 0xab]);
assert_eq!(bytes.write_at(3, &u16::to_be(0x89ab)), Err(()));
assert_eq!(bytes.write_at(4, &u16::to_be(0x89ab)), Err(()));
assert_eq!([].write_at(0, &u32::to_be(0x89ab)), Err(()));
}
}