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|
//! An improved `BufRead` interface.
extern crate flate2;
extern crate bzip2;
use std::io;
use std::io::{Error,ErrorKind};
use std::cmp;
use std::fmt;
mod generic;
mod memory;
mod limitor;
mod decompress;
pub use self::generic::BufferedReaderGeneric;
pub use self::memory::BufferedReaderMemory;
pub use self::limitor::BufferedReaderLimitor;
pub use self::decompress::BufferedReaderDeflate;
pub use self::decompress::BufferedReaderZlib;
pub use self::decompress::BufferedReaderBzip;
// The default buffer size.
const DEFAULT_BUF_SIZE: usize = 8 * 1024;
/// A `BufferedReader` is a type of `Read`er that has an internal
/// buffer, and allows working directly from that buffer. Like a
/// `BufRead`er, the internal buffer amortizes system calls. And,
/// like a `BufRead`, a `BufferedReader` exposes the internal buffer
/// so that a user can work with the data in place rather than having
/// to first copy it to a local buffer. However, unlike `BufRead`,
/// `BufferedReader` allows the caller to ensure that the internal
/// buffer has a certain amount of data.
pub trait BufferedReader<C> : io::Read + fmt::Debug {
/// Return the data in the internal buffer. Normally, the
/// returned buffer will contain *at least* `amount` bytes worth
/// of data. Less data may be returned if (and only if) the end
/// of the file is reached or an error occurs. In these cases,
/// any remaining data is returned. Note: the error is not
/// discarded, but will be returned when data is called and the
/// internal buffer is empty.
///
/// This function does not advance the cursor. Thus, multiple
/// calls will return the same data. To advance the cursor, use
/// `consume`.
fn data(&mut self, amount: usize) -> Result<&[u8], io::Error>;
/// Like `data`, but returns an error if there is not at least
/// `amount` bytes available.
fn data_hard(&mut self, amount: usize) -> Result<&[u8], io::Error> {
let result = self.data(amount);
if let Ok(buffer) = result {
if buffer.len() < amount {
return Err(Error::new(ErrorKind::UnexpectedEof, "unepxected EOF"));
}
}
return result;
}
/// Return all of the data until EOF. Like `data`, this does not
/// actually consume the data that is read.
///
/// In general, you shouldn't use this function as it can cause an
/// enormous amount of buffering. But, if you know that the
/// amount of data is limited, this is acceptable.
fn data_eof(&mut self) -> Result<&[u8], io::Error> {
// Don't just read std::usize::MAX bytes at once. The
// implementation might try to actually allocate a buffer that
// large! Instead, try with increasingly larger buffers until
// the read is (strictly) shorter than the specified size.
let mut s = DEFAULT_BUF_SIZE;
while s < std::usize::MAX {
match self.data(s) {
Ok(ref buffer) =>
if buffer.len() < s {
// We really want to do
//
// return Ok(buffer);
//
// But, the borrower checker won't let us:
//
// error[E0499]: cannot borrow `*self` as
// mutable more than once at a time.
//
// Instead, we break out of the loop, and then
// call self.data(s) again. This extra call
// shouldn't have any significant cost,
// because the buffer should already be
// prepared.
break;
} else {
s *= 2;
},
Err(err) =>
return Err(err),
}
}
return self.data(s);
}
/// Mark the first `amount` bytes of the internal buffer as
/// consumed. It is an error to call this function without having
/// first successfully called `data` (or a related function) to
/// buffer `amount` bytes.
///
/// This function returns the data that has been consumed.
fn consume(&mut self, amount: usize) -> &[u8];
/// This is a convenient function that effectively combines data()
/// and consume().
fn data_consume(&mut self, amount: usize)
-> Result<&[u8], std::io::Error>;
// This is a convenient function that effectively combines
// data_hard() and consume().
fn data_consume_hard(&mut self, amount: usize) -> Result<&[u8], io::Error>;
/// A convenience function for reading a 16-bit unsigned integer
/// in big endian format.
fn read_be_u16(&mut self) -> Result<u16, std::io::Error> {
let input = self.data_consume_hard(2)?;
return Ok(((input[0] as u16) << 8) + (input[1] as u16));
}
/// A convenience function for reading a 32-bit unsigned integer
/// in big endian format.
fn read_be_u32(&mut self) -> Result<u32, std::io::Error> {
let input = self.data_consume_hard(4)?;
return Ok(((input[0] as u32) << 24) + ((input[1] as u32) << 16)
+ ((input[2] as u32) << 8) + (input[3] as u32));
}
/// Reads and consumes `amount` bytes, and returns them in a
/// caller owned buffer. Implementations may optimize this to
/// avoid a copy.
fn steal(&mut self, amount: usize) -> Result<Vec<u8>, std::io::Error> {
let mut data = self.data_consume_hard(amount)?;
assert!(data.len() >= amount);
if data.len() > amount {
data = &data[..amount];
}
return Ok(data.to_vec());
}
/// Like steal, but instead of stealing a fixed number of bytes,
/// it steals all of the data it can.
fn steal_eof(&mut self) -> Result<Vec<u8>, std::io::Error> {
let len = self.data_eof()?.len();
let data = self.steal(len)?;
return Ok(data);
}
/// Like steal_eof, but instead of returning the data, the data is
/// discarded.
fn drop_eof(&mut self) -> Result<(), std::io::Error> {
loop {
match self.data_consume(DEFAULT_BUF_SIZE) {
Ok(ref buffer) =>
if buffer.len() < DEFAULT_BUF_SIZE {
// EOF.
break;
},
Err(err) =>
return Err(err),
}
}
Ok(())
}
fn into_inner<'a>(self: Box<Self>) -> Option<
|