zip/
crc32.rs

Help
1//! Helper module to compute a CRC32 checksum
2
3use std::io;
4use std::io::prelude::*;
5
6use crc32fast::Hasher;
7
8/// Reader that validates the CRC32 when it reaches the EOF.
9pub struct Crc32Reader<R> {
10    inner: R,
11    hasher: Hasher,
12    check: u32,
13    /// Signals if `inner` stores aes encrypted data.
14    /// AE-2 encrypted data doesn't use crc and sets the value to 0.
15    enabled: bool,
16}
17
18impl<R> Crc32Reader<R> {
19    /// Get a new Crc32Reader which checks the inner reader against checksum.
20    /// The check is disabled if `ae2_encrypted == true`.
21    pub(crate) fn new(inner: R, checksum: u32, ae2_encrypted: bool) -> Crc32Reader<R> {
22        Crc32Reader {
23            inner,
24            hasher: Hasher::new(),
25            check: checksum,
26            enabled: !ae2_encrypted,
27        }
28    }
29
30    fn check_matches(&self) -> bool {
31        self.check == self.hasher.clone().finalize()
32    }
33
34    pub fn into_inner(self) -> R {
35        self.inner
36    }
37}
38
39#[cold]
40fn invalid_checksum() -> io::Error {
41    io::Error::new(io::ErrorKind::InvalidData, "Invalid checksum")
42}
43
44impl<R: Read> Read for Crc32Reader<R> {
45    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
46        let count = self.inner.read(buf)?;
47
48        if self.enabled {
49            if count == 0 && !buf.is_empty() && !self.check_matches() {
50                return Err(invalid_checksum());
51            }
52            self.hasher.update(&buf[..count]);
53        }
54        Ok(count)
55    }
56
57    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
58        let start = buf.len();
59        let n = self.inner.read_to_end(buf)?;
60
61        if self.enabled {
62            self.hasher.update(&buf[start..]);
63            if !self.check_matches() {
64                return Err(invalid_checksum());
65            }
66        }
67
68        Ok(n)
69    }
70
71    fn read_to_string(&mut self, buf: &mut String) -> io::Result<usize> {
72        let start = buf.len();
73        let n = self.inner.read_to_string(buf)?;
74
75        if self.enabled {
76            self.hasher.update(&buf.as_bytes()[start..]);
77            if !self.check_matches() {
78                return Err(invalid_checksum());
79            }
80        }
81
82        Ok(n)
83    }
84}
85
86#[cfg(test)]
87mod test {
88    use super::*;
89
90    #[test]
91    fn test_empty_reader() {
92        let data: &[u8] = b"";
93        let mut buf = [0; 1];
94
95        let mut reader = Crc32Reader::new(data, 0, false);
96        assert_eq!(reader.read(&mut buf).unwrap(), 0);
97
98        let mut reader = Crc32Reader::new(data, 1, false);
99        assert!(reader
100            .read(&mut buf)
101            .unwrap_err()
102            .to_string()
103            .contains("Invalid checksum"));
104    }
105
106    #[test]
107    fn test_byte_by_byte() {
108        let data: &[u8] = b"1234";
109        let mut buf = [0; 1];
110
111        let mut reader = Crc32Reader::new(data, 0x9be3e0a3, false);
112        assert_eq!(reader.read(&mut buf).unwrap(), 1);
113        assert_eq!(reader.read(&mut buf).unwrap(), 1);
114        assert_eq!(reader.read(&mut buf).unwrap(), 1);
115        assert_eq!(reader.read(&mut buf).unwrap(), 1);
116        assert_eq!(reader.read(&mut buf).unwrap(), 0);
117        // Can keep reading 0 bytes after the end
118        assert_eq!(reader.read(&mut buf).unwrap(), 0);
119    }
120
121    #[test]
122    fn test_zero_read() {
123        let data: &[u8] = b"1234";
124        let mut buf = [0; 5];
125
126        let mut reader = Crc32Reader::new(data, 0x9be3e0a3, false);
127        assert_eq!(reader.read(&mut buf[..0]).unwrap(), 0);
128        assert_eq!(reader.read(&mut buf).unwrap(), 4);
129    }
130}
zip/crc32.rs

zip/
crc32.rs
