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Diffstat (limited to 'media/libaom/src/third_party/libyuv/source/mjpeg_validate.cc')
-rw-r--r-- | media/libaom/src/third_party/libyuv/source/mjpeg_validate.cc | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/media/libaom/src/third_party/libyuv/source/mjpeg_validate.cc b/media/libaom/src/third_party/libyuv/source/mjpeg_validate.cc new file mode 100644 index 000000000..8edfbe1e7 --- /dev/null +++ b/media/libaom/src/third_party/libyuv/source/mjpeg_validate.cc @@ -0,0 +1,101 @@ +/* + * 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 + +// Enable this to try scasb implementation. +// #define ENABLE_SCASB 1 + +#ifdef ENABLE_SCASB + +// Multiple of 1. +__declspec(naked) +const uint8* ScanRow_ERMS(const uint8* src, uint32 val, int count) { + __asm { + mov edx, edi + mov edi, [esp + 4] // src + mov eax, [esp + 8] // val + mov ecx, [esp + 12] // count + repne scasb + jne sr99 + mov eax, edi + sub eax, 1 + mov edi, edx + ret + + sr99: + mov eax, 0 + mov edi, edx + ret + } +} +#endif + +// Helper function to scan for EOI marker. +static LIBYUV_BOOL ScanEOI(const uint8* sample, size_t sample_size) { + const uint8* end = sample + sample_size - 1; + const uint8* it = sample; + for (;;) { +#ifdef ENABLE_SCASB + it = ScanRow_ERMS(it, 0xff, end - it); +#else + it = static_cast<const uint8*>(memchr(it, 0xff, end - it)); +#endif + 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) { + const size_t kBackSearchSize = 1024; + if (sample_size < 64) { + // ERROR: Invalid jpeg size: sample_size + return LIBYUV_FALSE; + } + if (sample[0] != 0xff || sample[1] != 0xd8) { // Start Of Image + // ERROR: Invalid jpeg initial start code + return LIBYUV_FALSE; + } + // Step over SOI marker. + sample += 2; + sample_size -= 2; + + // Look for the End Of Image (EOI) marker in the end kilobyte 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; + } + return ScanEOI(sample, sample_size); + +} + +#ifdef __cplusplus +} // extern "C" +} // namespace libyuv +#endif + |