text: /*
   *  Copyright 2012 The LibYuv Project Authors. All rights reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree. An additional intellectual property rights grant can be found
   *  in the file PATENTS. All contributing project authors may
   *  be found in the AUTHORS file in the root of the source tree.
   */
  
  #include "mjpeg_decoder.h"
  
  #include <string.h>  // For memchr.
  
  #ifdef __cplusplus
  namespace libyuv {
  extern "C" {
  #endif
  
  // Helper function to scan for EOI marker (0xff 0xd9).
  static LIBYUV_BOOL ScanEOI(const uint8* sample, size_t sample_size) {
    if (sample_size >= 2) {
      const uint8* end = sample + sample_size - 1;
      const uint8* it = sample;
      while (it < end) {
        // TODO(fbarchard): scan for 0xd9 instead.
        it = static_cast<const uint8 *>(memchr(it, 0xff, end - it));
        if (it == NULL) {
          break;
        }
        if (it[1] == 0xd9) {
          return LIBYUV_TRUE;  // Success: Valid jpeg.
        }
        ++it;  // Skip over current 0xff.
      }
    }
    // ERROR: Invalid jpeg end code not found. Size sample_size
    return LIBYUV_FALSE;
  }
  
  // Helper function to validate the jpeg appears intact.
  LIBYUV_BOOL ValidateJpeg(const uint8* sample, size_t sample_size) {
    // Maximum size that ValidateJpeg will consider valid.
    const size_t kMaxJpegSize = 0x7fffffffull;
    const size_t kBackSearchSize = 1024;
    if (sample_size < 64 || sample_size > kMaxJpegSize || !sample) {
      // ERROR: Invalid jpeg size: sample_size
      return LIBYUV_FALSE;
    }
    if (sample[0] != 0xff || sample[1] != 0xd8) {  // SOI marker
      // ERROR: Invalid jpeg initial start code
      return LIBYUV_FALSE;
    }
  
    // Look for the End Of Image (EOI) marker near the end of the buffer.
    if (sample_size > kBackSearchSize) {
      if (ScanEOI(sample + sample_size - kBackSearchSize, kBackSearchSize)) {
        return LIBYUV_TRUE;  // Success: Valid jpeg.
      }
      // Reduce search size for forward search.
      sample_size = sample_size - kBackSearchSize + 1;
    }
    // Step over SOI marker and scan for EOI.
    return ScanEOI(sample + 2, sample_size - 2);
  }
  
  #ifdef __cplusplus
  }  // extern "C"
  }  // namespace libyuv
  #endif
  
  