exif/
jpeg.rs

1//
2// Copyright (c) 2016 KAMADA Ken'ichi.
3// All rights reserved.
4//
5// Redistribution and use in source and binary forms, with or without
6// modification, are permitted provided that the following conditions
7// are met:
8// 1. Redistributions of source code must retain the above copyright
9//    notice, this list of conditions and the following disclaimer.
10// 2. Redistributions in binary form must reproduce the above copyright
11//    notice, this list of conditions and the following disclaimer in the
12//    documentation and/or other materials provided with the distribution.
13//
14// THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17// ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20// OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24// SUCH DAMAGE.
25//
26
27use std::io::{BufRead, ErrorKind};
28
29use crate::error::Error;
30use crate::util::{read8, read16};
31
32mod marker {
33    // The first byte of a marker.
34    pub const P:    u8 = 0xff;
35    // Marker codes.
36    pub const Z:    u8 = 0x00;		// Not a marker but a byte stuffing.
37    pub const TEM:  u8 = 0x01;
38    pub const RST0: u8 = 0xd0;
39    pub const RST7: u8 = 0xd7;
40    pub const SOI:  u8 = 0xd8;
41    pub const EOI:  u8 = 0xd9;
42    pub const SOS:  u8 = 0xda;
43    pub const APP1: u8 = 0xe1;
44}
45
46// SOI marker as the JPEG header.
47const JPEG_SIG: [u8; 2] = [marker::P, marker::SOI];
48
49// Exif identifier code "Exif\0\0". [EXIF23 4.7.2]
50const EXIF_ID: [u8; 6] = [0x45, 0x78, 0x69, 0x66, 0x00, 0x00];
51
52/// Get the Exif attribute information segment from a JPEG file.
53pub fn get_exif_attr<R>(reader: &mut R)
54                        -> Result<Vec<u8>, Error> where R: BufRead {
55    match get_exif_attr_sub(reader) {
56        Err(Error::Io(ref e)) if e.kind() == ErrorKind::UnexpectedEof =>
57            Err(Error::InvalidFormat("Broken JPEG file")),
58        r => r,
59    }
60}
61
62fn get_exif_attr_sub<R>(reader: &mut R)
63                        -> Result<Vec<u8>, Error> where R: BufRead {
64    let mut soi = [0u8; 2];
65    reader.read_exact(&mut soi)?;
66    if soi != [marker::P, marker::SOI] {
67        return Err(Error::InvalidFormat("Not a JPEG file"));
68    }
69    loop {
70        // Find a marker prefix.  Discard non-ff bytes, which appear if
71        // we are in the scan data after SOS or we are out of sync.
72        reader.read_until(marker::P, &mut Vec::new())?;
73        // Get a marker code.
74        let mut code;
75        loop {
76            code = read8(reader)?;
77            if code != marker::P { break; }
78        }
79        // Continue or return early on stand-alone markers.
80        match code {
81            marker::Z | marker::TEM | marker::RST0..=marker::RST7 => continue,
82            marker::SOI => return Err(Error::InvalidFormat("Unexpected SOI")),
83            marker::EOI => return Err(Error::NotFound("JPEG")),
84            _ => {},
85        }
86        // Read marker segments.
87        let len = read16(reader)?.checked_sub(2)
88            .ok_or(Error::InvalidFormat("Invalid segment length"))?;
89        let mut seg = vec![0; len.into()];
90        reader.read_exact(&mut seg)?;
91        if code == marker::APP1 && seg.starts_with(&EXIF_ID) {
92            seg.drain(..EXIF_ID.len());
93            return Ok(seg);
94        }
95        if code == marker::SOS {
96            // Skipping the scan data is handled in the main loop,
97            // so there is nothing to do here.
98        }
99    }
100}
101
102pub fn is_jpeg(buf: &[u8]) -> bool {
103    buf.starts_with(&JPEG_SIG)
104}
105
106#[cfg(test)]
107mod tests {
108    use super::*;
109
110    #[test]
111    fn truncated() {
112        let sets: &[&[u8]] = &[
113            b"",
114            b"\xff",
115            b"\xff\xd8",
116            b"\xff\xd8\x00",
117            b"\xff\xd8\xff",
118            b"\xff\xd8\xff\xe1\x00\x08\x03\x04",
119        ];
120        for &data in sets {
121            assert_err_pat!(get_exif_attr(&mut &data[..]),
122                            Error::InvalidFormat("Broken JPEG file"));
123        }
124
125        let mut data = b"\xff\xd8\xff\xe1\x00\x08Exif\0\0".to_vec();
126        assert_eq!(get_exif_attr(&mut &data[..]).unwrap(), b"");
127        while let Some(_) = data.pop() {
128            get_exif_attr(&mut &data[..]).unwrap_err();
129        }
130    }
131
132    #[test]
133    fn no_exif() {
134        let data = b"\xff\xd8\xff\xd9";
135        assert_err_pat!(get_exif_attr(&mut &data[..]),
136                        Error::NotFound(_));
137    }
138
139    #[test]
140    fn out_of_sync() {
141        let data = b"\xff\xd8\x01\x02\x03\xff\x00\xff\xd9";
142        assert_err_pat!(get_exif_attr(&mut &data[..]),
143                        Error::NotFound(_));
144    }
145
146    #[test]
147    fn empty() {
148        let data = b"\xff\xd8\xff\xe1\x00\x08Exif\0\0\xff\xd9";
149        assert_ok!(get_exif_attr(&mut &data[..]), []);
150    }
151
152    #[test]
153    fn non_empty() {
154        let data = b"\xff\xd8\xff\xe1\x00\x0aExif\0\0\xbe\xad\xff\xd9";
155        assert_ok!(get_exif_attr(&mut &data[..]), [0xbe, 0xad]);
156    }
157}
exif/jpeg.rs

exif/
jpeg.rs
