Line data    Source code

       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).
      21           0 : static LIBYUV_BOOL ScanEOI(const uint8* sample, size_t sample_size) {
      22           0 :   if (sample_size >= 2) {
      23           0 :     const uint8* end = sample + sample_size - 1;
      24           0 :     const uint8* it = sample;
      25           0 :     while (it < end) {
      26             :       // TODO(fbarchard): scan for 0xd9 instead.
      27           0 :       it = static_cast<const uint8*>(memchr(it, 0xff, end - it));
      28           0 :       if (it == NULL) {
      29           0 :         break;
      30             :       }
      31           0 :       if (it[1] == 0xd9) {
      32           0 :         return LIBYUV_TRUE;  // Success: Valid jpeg.
      33             :       }
      34           0 :       ++it;  // Skip over current 0xff.
      35             :     }
      36             :   }
      37             :   // ERROR: Invalid jpeg end code not found. Size sample_size
      38           0 :   return LIBYUV_FALSE;
      39             : }
      40             : 
      41             : // Helper function to validate the jpeg appears intact.
      42           0 : LIBYUV_BOOL ValidateJpeg(const uint8* sample, size_t sample_size) {
      43             :   // Maximum size that ValidateJpeg will consider valid.
      44           0 :   const size_t kMaxJpegSize = 0x7fffffffull;
      45           0 :   const size_t kBackSearchSize = 1024;
      46           0 :   if (sample_size < 64 || sample_size > kMaxJpegSize || !sample) {
      47             :     // ERROR: Invalid jpeg size: sample_size
      48           0 :     return LIBYUV_FALSE;
      49             :   }
      50           0 :   if (sample[0] != 0xff || sample[1] != 0xd8) {  // SOI marker
      51             :     // ERROR: Invalid jpeg initial start code
      52           0 :     return LIBYUV_FALSE;
      53             :   }
      54             : 
      55             :   // Look for the End Of Image (EOI) marker near the end of the buffer.
      56           0 :   if (sample_size > kBackSearchSize) {
      57           0 :     if (ScanEOI(sample + sample_size - kBackSearchSize, kBackSearchSize)) {
      58           0 :       return LIBYUV_TRUE;  // Success: Valid jpeg.
      59             :     }
      60             :     // Reduce search size for forward search.
      61           0 :     sample_size = sample_size - kBackSearchSize + 1;
      62             :   }
      63             :   // Step over SOI marker and scan for EOI.
      64           0 :   return ScanEOI(sample + 2, sample_size - 2);
      65             : }
      66             : 
      67             : #ifdef __cplusplus
      68             : }  // extern "C"
      69             : }  // namespace libyuv
      70             : #endif