b3c836d9c3
The caller can pass in an empty slice for reading, which should return `Ok(0)`, not raise an error about an invalid checksum prematurely
100 lines
2.4 KiB
Rust
100 lines
2.4 KiB
Rust
//! Helper module to compute a CRC32 checksum
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use std::io;
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use std::io::prelude::*;
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use crc32fast::Hasher;
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/// Reader that validates the CRC32 when it reaches the EOF.
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pub struct Crc32Reader<R>
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{
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inner: R,
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hasher: Hasher,
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check: u32,
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}
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impl<R> Crc32Reader<R>
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{
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/// Get a new Crc32Reader which check the inner reader against checksum.
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pub fn new(inner: R, checksum: u32) -> Crc32Reader<R>
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{
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Crc32Reader
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{
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inner: inner,
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hasher: Hasher::new(),
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check: checksum,
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}
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}
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fn check_matches(&self) -> bool
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{
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self.check == self.hasher.clone().finalize()
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}
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pub fn into_inner(self) -> R {
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self.inner
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}
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}
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impl<R: Read> Read for Crc32Reader<R>
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{
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fn read(&mut self, buf: &mut [u8]) -> io::Result<usize>
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{
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let count = match self.inner.read(buf)
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{
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Ok(0) if !buf.is_empty() && !self.check_matches() => { return Err(io::Error::new(io::ErrorKind::Other, "Invalid checksum")) },
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Ok(n) => n,
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Err(e) => return Err(e),
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};
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self.hasher.update(&buf[0..count]);
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Ok(count)
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}
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}
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#[cfg(test)]
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mod test
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{
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use super::*;
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use std::io::Read;
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use std::io::Cursor;
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#[test]
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fn test_empty_reader()
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{
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let data: &[u8] = b"";
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let mut buf = [0; 1];
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let mut reader = Crc32Reader::new(data, 0);
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assert_eq!(reader.read(&mut buf).unwrap(), 0);
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let mut reader = Crc32Reader::new(data, 1);
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assert!(reader.read(&mut buf).unwrap_err().to_string().contains("Invalid checksum"));
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}
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#[test]
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fn test_byte_by_byte()
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{
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let data: &[u8] = b"1234";
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let mut buf = [0; 1];
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let mut reader = Crc32Reader::new(data, 0x9be3e0a3);
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assert_eq!(reader.read(&mut buf).unwrap(), 1);
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assert_eq!(reader.read(&mut buf).unwrap(), 1);
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assert_eq!(reader.read(&mut buf).unwrap(), 1);
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assert_eq!(reader.read(&mut buf).unwrap(), 1);
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assert_eq!(reader.read(&mut buf).unwrap(), 0);
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// Can keep reading 0 bytes after the end
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assert_eq!(reader.read(&mut buf).unwrap(), 0);
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}
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#[test]
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fn test_zero_read()
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{
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let data: &[u8] = b"1234";
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let mut buf = [0; 5];
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let mut reader = Crc32Reader::new(data, 0x9be3e0a3);
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assert_eq!(reader.read(&mut buf[..0]).unwrap(), 0);
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assert_eq!(reader.read(&mut buf).unwrap(), 4);
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}
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}
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