1 /*
2  *  Copyright 2012 The LibYuv Project Authors. All rights reserved.
3  *
4  *  Use of this source code is governed by a BSD-style license
5  *  that can be found in the LICENSE file in the root of the source
6  *  tree. An additional intellectual property rights grant can be found
7  *  in the file PATENTS. All contributing project authors may
8  *  be found in the AUTHORS file in the root of the source tree.
9  */
10 
11 #include "libyuv/mjpeg_decoder.h"
12 
13 #include <string.h>  // For memchr.
14 
15 #ifdef __cplusplus
16 namespace libyuv {
17 extern "C" {
18 #endif
19 
20 // Helper function to scan for EOI marker (0xff 0xd9).
ScanEOI(const uint8 * sample,size_t sample_size)21 static LIBYUV_BOOL ScanEOI(const uint8* sample, size_t sample_size) {
22   if (sample_size >= 2) {
23     const uint8* end = sample + sample_size - 1;
24     const uint8* it = sample;
25     while (it < end) {
26       // TODO(fbarchard): scan for 0xd9 instead.
27       it = static_cast<const uint8*>(memchr(it, 0xff, end - it));
28       if (it == NULL) {
29         break;
30       }
31       if (it[1] == 0xd9) {
32         return LIBYUV_TRUE;  // Success: Valid jpeg.
33       }
34       ++it;  // Skip over current 0xff.
35     }
36   }
37   // ERROR: Invalid jpeg end code not found. Size sample_size
38   return LIBYUV_FALSE;
39 }
40 
41 // Helper function to validate the jpeg appears intact.
ValidateJpeg(const uint8 * sample,size_t sample_size)42 LIBYUV_BOOL ValidateJpeg(const uint8* sample, size_t sample_size) {
43   // Maximum size that ValidateJpeg will consider valid.
44   const size_t kMaxJpegSize = 0x7fffffffull;
45   const size_t kBackSearchSize = 1024;
46   if (sample_size < 64 || sample_size > kMaxJpegSize || !sample) {
47     // ERROR: Invalid jpeg size: sample_size
48     return LIBYUV_FALSE;
49   }
50   if (sample[0] != 0xff || sample[1] != 0xd8) {  // SOI marker
51     // ERROR: Invalid jpeg initial start code
52     return LIBYUV_FALSE;
53   }
54 
55   // Look for the End Of Image (EOI) marker near the end of the buffer.
56   if (sample_size > kBackSearchSize) {
57     if (ScanEOI(sample + sample_size - kBackSearchSize, kBackSearchSize)) {
58       return LIBYUV_TRUE;  // Success: Valid jpeg.
59     }
60     // Reduce search size for forward search.
61     sample_size = sample_size - kBackSearchSize + 1;
62   }
63   // Step over SOI marker and scan for EOI.
64   return ScanEOI(sample + 2, sample_size - 2);
65 }
66 
67 #ifdef __cplusplus
68 }  // extern "C"
69 }  // namespace libyuv
70 #endif
71