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