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#[cfg(feature = "tokio")]
use std::future::Future;
use std::io::Read;
use std::io::{Error, ErrorKind};
#[cfg(feature = "tokio")]
use tokio::io::{AsyncRead, AsyncReadExt};
use crate::PcapError;
/// Internal structure that bufferize its input and allow to parse element from its buffer.
#[derive(Debug)]
pub(crate) struct ReadBuffer<R> {
/// Reader from which we read the data from
reader: R,
/// Internal buffer
buffer: Vec<u8>,
/// Current start position of the buffer
pos: usize,
/// Current end position of the buffer
len: usize,
}
impl<R> ReadBuffer<R> {
/// Creates a new ReadBuffer with capacity of 8_000_000
pub fn new(reader: R) -> Self {
Self::with_capacity(reader, 8_000_000)
}
/// Creates a new ReadBuffer with the given capacity
pub fn with_capacity(reader: R, capacity: usize) -> Self {
Self { reader, buffer: vec![0_u8; capacity], pos: 0, len: 0 }
}
/// Advance the internal buffer position.
fn advance(&mut self, nb_bytes: usize) {
assert!(self.pos + nb_bytes <= self.len);
self.pos += nb_bytes;
}
/// Reset pos
pub(crate) fn reset_pos(&mut self) {
self.pos = 0;
}
/// Advance the internal buffer position.
fn advance_with_slice(&mut self, rem: &[u8]) {
// Compute the length between the buffer and the slice
let diff_len = (rem.as_ptr() as usize)
.checked_sub(self.buffer().as_ptr() as usize)
.expect("Rem is not a sub slice of self.buffer");
self.advance(diff_len)
}
/// Return the valid data of the internal buffer
pub fn buffer(&self) -> &[u8] {
&self.buffer[self.pos..self.len]
}
/// Return the inner reader
pub fn into_inner(self) -> R {
self.reader
}
/// Return a reference over the inner reader
pub fn get_ref(&self) -> &R {
&self.reader
}
}
impl<R> AsRef<R> for ReadBuffer<R> {
fn as_ref(&self) -> &R {
&self.reader
}
}
impl<R> AsMut<R> for ReadBuffer<R> {
fn as_mut(&mut self) -> &mut R {
&mut self.reader
}
}
impl<R: Read> ReadBuffer<R> {
/// Parse data from the internal buffer
///
/// Safety
///
/// The parser must NOT keep a reference to the buffer in input.
pub fn parse_with<'a, 'b: 'a, 'c: 'a, F, O>(&'c mut self, mut parser: F) -> Result<O, PcapError>
where
F: FnMut(&'a [u8]) -> Result<(&'a [u8], O), PcapError>,
F: 'b,
O: 'a,
{
loop {
let buf = &self.buffer[self.pos..self.len];
// Sound because 'b and 'c must outlive 'a so the buffer cannot be modified while someone has a ref on it
let buf: &'a [u8] = unsafe { std::mem::transmute(buf) };
match parser(buf) {
Ok((rem, value)) => {
self.advance_with_slice(rem);
return Ok(value);
},
Err(PcapError::IncompleteBuffer) => {
// The parsed data len should never be more than the buffer capacity
if buf.len() == self.buffer.len() {
return Err(PcapError::IoError(Error::from(ErrorKind::UnexpectedEof)));
}
let nb_read = self.fill_buf().map_err(PcapError::IoError)?;
if nb_read == 0 {
return Err(PcapError::IoError(Error::from(ErrorKind::UnexpectedEof)));
}
},
Err(e) => return Err(e),
}
}
}
/// Fill the inner buffer.
/// Copy the remaining data inside buffer at its start and the fill the end part with data from the reader.
fn fill_buf(&mut self) -> Result<usize, std::io::Error> {
// Copy the remaining data to the start of the buffer
let rem_len = unsafe {
let buf_ptr_mut = self.buffer.as_mut_ptr();
let rem_ptr_mut = buf_ptr_mut.add(self.pos);
std::ptr::copy(rem_ptr_mut, buf_ptr_mut, self.len - self.pos);
self.len - self.pos
};
let nb_read = self.reader.read(&mut self.buffer[rem_len..])?;
self.len = rem_len + nb_read;
self.pos = 0;
Ok(nb_read)
}
/// Return true there are some data that can be read
pub fn has_data_left(&mut self) -> Result<bool, std::io::Error> {
// The buffer can be empty and the reader can still have data
if self.buffer().is_empty() {
let nb_read = self.fill_buf()?;
if nb_read == 0 {
return Ok(false);
}
}
Ok(true)
}
}
#[cfg(feature = "tokio")]
impl<R: AsyncRead + Unpin> ReadBuffer<R> {
pub async fn async_parse_with<'a, 'b: 'a, 'c: 'a, F, Fut, O>(&'c mut self, mut parser: F) -> Result<O, PcapError>
where
F: FnMut(&'a [u8]) -> Fut,
F: 'b,
Fut: Future<Output = Result<(&'a [u8], O), PcapError>> + 'a,
O: 'a,
{
self.async_parse_with_context((), move |_, src| {
let fut = parser(src);
async { (fut.await, ()) }
})
.await
}
/// Parse data from the internal buffer
///
/// Safety
///
/// The parser must NOT keep a reference to the buffer in input.
pub async fn async_parse_with_context<'a, 'b: 'a, 'c: 'a, Context, F, Fut, O>(
&'c mut self,
mut context: Context,
mut parser: F,
) -> Result<O, PcapError>
where
F: FnMut(Context, &'a [u8]) -> Fut,
F: 'b,
Fut: Future<Output = (Result<(&'a [u8], O), PcapError>, Context)> + 'a,
O: 'a,
{
loop {
let buf = &self.buffer[self.pos..self.len];
// Sound because 'b and 'c must outlive 'a so the buffer cannot be modified while someone has a ref on it
let buf: &'a [u8] = unsafe { std::mem::transmute(buf) };
let result = parser(context, buf).await;
context = result.1;
match result.0 {
Ok((rem, value)) => {
self.advance_with_slice(rem);
return Ok(value);
},
Err(PcapError::IncompleteBuffer) => {
// The parsed data len should never be more than the buffer capacity
if buf.len() == self.buffer.len() {
return Err(PcapError::IoError(Error::from(ErrorKind::UnexpectedEof)));
}
let nb_read = self.async_fill_buf().await.map_err(PcapError::IoError)?;
if nb_read == 0 {
return Err(PcapError::IoError(Error::from(ErrorKind::UnexpectedEof)));
}
},
Err(e) => return Err(e),
}
}
}
/// Fill the inner buffer.
/// Copy the remaining data inside buffer at its start and the fill the end part with data from the reader.
async fn async_fill_buf(&mut self) -> Result<usize, std::io::Error> {
// Copy the remaining data to the start of the buffer
let rem_len = unsafe {
let buf_ptr_mut = self.buffer.as_mut_ptr();
let rem_ptr_mut = buf_ptr_mut.add(self.pos);
std::ptr::copy(rem_ptr_mut, buf_ptr_mut, self.len - self.pos);
self.len - self.pos
};
let nb_read = self.reader.read(&mut self.buffer[rem_len..]).await?;
self.len = rem_len + nb_read;
self.pos = 0;
Ok(nb_read)
}
/// Return true there are some data that can be read
pub async fn async_has_data_left(&mut self) -> Result<bool, std::io::Error> {
// The buffer can be empty and the reader can still have data
if self.buffer().is_empty() {
let nb_read = self.async_fill_buf().await?;
if nb_read == 0 {
return Ok(false);
}
}
Ok(true)
}
}
#[cfg(test)]
mod test {
/*
// Shouldn't compile
#[test]
fn parse_with_safety() {
let a = &[0_u8; 10];
let b = &mut &a[..];
let input = vec![1_u8; 100];
let input_read = &mut &input[..];
let mut reader = super::ReadBuffer::new(input_read);
unsafe {
reader.parse_with(|buf| {
*b = buf;
Ok((buf, ()))
});
}
unsafe {
reader.has_data_left();
}
println!("{:?}", b);
}
*/
}