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|
//! Simple abstractions for the IO operations.
//!
//! Basically it just a replacement for the std::io that is usable from
//! the `no_std` environment.
#[cfg(feature="std")]
use std::io;
/// IO specific error.
#[derive(Debug)]
pub enum Error {
/// Some unexpected data left in the buffer after reading all data.
TrailingData,
/// Unexpected End-Of-File
UnexpectedEof,
/// Invalid data is encountered.
InvalidData,
#[cfg(feature = "std")]
IoError(std::io::Error),
}
/// IO specific Result.
pub type Result<T> = core::result::Result<T, Error>;
pub trait Write {
/// Write a buffer of data into this write.
///
/// All data is written at once.
fn write(&mut self, buf: &[u8]) -> Result<()>;
}
pub trait Read {
/// Read a data from this read to a buffer.
///
/// If there is not enough data in this read then `UnexpectedEof` will be returned.
fn read(&mut self, buf: &mut [u8]) -> Result<()>;
}
/// Reader that saves the last position.
pub struct Cursor<T> {
inner: T,
pos: usize,
}
impl<T> Cursor<T> {
pub fn new(inner: T) -> Cursor<T> {
Cursor {
inner,
pos: 0,
}
}
pub fn position(&self) -> usize {
self.pos
}
}
impl<T: AsRef<[u8]>> Read for Cursor<T> {
fn read(&mut self, buf: &mut [u8]) -> Result<()> {
let slice = self.inner.as_ref();
let remainder = slice.len() - self.pos;
let requested = buf.len();
if requested > remainder {
return Err(Error::UnexpectedEof);
}
buf.copy_from_slice(&slice[self.pos..(self.pos + requested)]);
self.pos += requested;
Ok(())
}
}
#[cfg(not(feature = "std"))]
impl Write for alloc::vec::Vec<u8> {
fn write(&mut self, buf: &[u8]) -> Result<()> {
self.extend(buf);
Ok(())
}
}
#[cfg(feature = "std")]
impl<T: io::Read> Read for T {
fn read(&mut self, buf: &mut [u8]) -> Result<()> {
self.read_exact(buf)
.map_err(Error::IoError)
}
}
#[cfg(feature = "std")]
impl<T: io::Write> Write for T {
fn write(&mut self, buf: &[u8]) -> Result<()> {
self.write_all(buf).map_err(Error::IoError)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn cursor() {
let mut cursor = Cursor::new(vec![0xFFu8, 0x7Fu8]);
assert_eq!(cursor.position(), 0);
let mut buf = [0u8];
assert!(cursor.read(&mut buf[..]).is_ok());
assert_eq!(cursor.position(), 1);
assert_eq!(buf[0], 0xFFu8);
assert!(cursor.read(&mut buf[..]).is_ok());
assert_eq!(buf[0], 0x7Fu8);
assert_eq!(cursor.position(), 2);
}
#[test]
fn overflow_in_cursor() {
let mut cursor = Cursor::new(vec![0u8]);
let mut buf = [0, 1, 2];
assert!(cursor.read(&mut buf[..]).is_err());
}
}
|
