223bf29307
MIPS build fixes https://code.google.com/p/webm/issues/detail?id=957 Change-Id: I9d53900af36d783c369b5dff27a7479cb94fd16b
102 lines
2.6 KiB
C++
102 lines
2.6 KiB
C++
/*
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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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// Enable this to try scasb implementation.
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// #define ENABLE_SCASB 1
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#ifdef ENABLE_SCASB
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// Multiple of 1.
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__declspec(naked) __declspec(align(16))
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const uint8* ScanRow_ERMS(const uint8* src, uint32 val, int count) {
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__asm {
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mov edx, edi
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mov edi, [esp + 4] // src
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mov eax, [esp + 8] // val
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mov ecx, [esp + 12] // count
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repne scasb
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jne sr99
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mov eax, edi
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sub eax, 1
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mov edi, edx
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ret
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sr99:
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mov eax, 0
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mov edi, edx
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ret
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}
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}
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#endif
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// Helper function to scan for EOI marker.
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static LIBYUV_BOOL ScanEOI(const uint8* sample, size_t sample_size) {
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const uint8* end = sample + sample_size - 1;
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const uint8* it = sample;
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for (;;) {
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#ifdef ENABLE_SCASB
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it = ScanRow_ERMS(it, 0xff, end - it);
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#else
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it = static_cast<const uint8*>(memchr(it, 0xff, end - it));
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#endif
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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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// 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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const size_t kBackSearchSize = 1024;
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if (sample_size < 64) {
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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) { // Start Of Image
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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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// Step over SOI marker.
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sample += 2;
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sample_size -= 2;
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// Look for the End Of Image (EOI) marker in the end kilobyte 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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return ScanEOI(sample, sample_size);
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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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