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/*
* 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 "libyuv/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_t* sample, size_t sample_size) {
if (sample_size >= 2) {
const uint8_t* end = sample + sample_size - 1;
const uint8_t* it = sample;
while (it < end) {
// TODO(fbarchard): scan for 0xd9 instead.
it = (const uint8_t*)(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_t* 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
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