/*
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* Copyright 2015 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#include "SkJpegUtility.h"
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#include "SkCodecPriv.h"
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/*
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* Call longjmp to continue execution on an error
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*/
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void skjpeg_err_exit(j_common_ptr dinfo) {
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// Simply return to Skia client code
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// JpegDecoderMgr will take care of freeing memory
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skjpeg_error_mgr* error = (skjpeg_error_mgr*) dinfo->err;
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(*error->output_message) (dinfo);
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if (error->fJmpBufStack.empty()) {
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SK_ABORT("JPEG error with no jmp_buf set.");
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}
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longjmp(*error->fJmpBufStack.back(), 1);
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}
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// Functions for buffered sources //
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/*
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* Initialize the buffered source manager
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*/
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static void sk_init_buffered_source(j_decompress_ptr dinfo) {
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skjpeg_source_mgr* src = (skjpeg_source_mgr*) dinfo->src;
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src->next_input_byte = (const JOCTET*) src->fBuffer;
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src->bytes_in_buffer = 0;
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}
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/*
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* Fill the input buffer from the stream
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*/
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static boolean sk_fill_buffered_input_buffer(j_decompress_ptr dinfo) {
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skjpeg_source_mgr* src = (skjpeg_source_mgr*) dinfo->src;
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size_t bytes = src->fStream->read(src->fBuffer, skjpeg_source_mgr::kBufferSize);
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// libjpeg is still happy with a less than full read, as long as the result is non-zero
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if (bytes == 0) {
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// Let libjpeg know that the buffer needs to be refilled
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src->next_input_byte = nullptr;
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src->bytes_in_buffer = 0;
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return false;
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}
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src->next_input_byte = (const JOCTET*) src->fBuffer;
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src->bytes_in_buffer = bytes;
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return true;
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}
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/*
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* Skip a certain number of bytes in the stream
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*/
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static void sk_skip_buffered_input_data(j_decompress_ptr dinfo, long numBytes) {
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skjpeg_source_mgr* src = (skjpeg_source_mgr*) dinfo->src;
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size_t bytes = (size_t) numBytes;
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if (bytes > src->bytes_in_buffer) {
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size_t bytesToSkip = bytes - src->bytes_in_buffer;
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if (bytesToSkip != src->fStream->skip(bytesToSkip)) {
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SkCodecPrintf("Failure to skip.\n");
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dinfo->err->error_exit((j_common_ptr) dinfo);
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return;
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}
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src->next_input_byte = (const JOCTET*) src->fBuffer;
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src->bytes_in_buffer = 0;
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} else {
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src->next_input_byte += numBytes;
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src->bytes_in_buffer -= numBytes;
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}
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}
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/*
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* We do not need to do anything to terminate our stream
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*/
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static void sk_term_source(j_decompress_ptr dinfo)
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{
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// The current implementation of SkJpegCodec does not call
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// jpeg_finish_decompress(), so this function is never called.
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// If we want to modify this function to do something, we also
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// need to modify SkJpegCodec to call jpeg_finish_decompress().
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}
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// Functions for memory backed sources //
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/*
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* Initialize the mem backed source manager
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*/
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static void sk_init_mem_source(j_decompress_ptr dinfo) {
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/* no work necessary here, all things are done in constructor */
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}
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static void sk_skip_mem_input_data (j_decompress_ptr cinfo, long num_bytes) {
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jpeg_source_mgr* src = cinfo->src;
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size_t bytes = static_cast<size_t>(num_bytes);
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if(bytes > src->bytes_in_buffer) {
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src->next_input_byte = nullptr;
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src->bytes_in_buffer = 0;
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} else {
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src->next_input_byte += bytes;
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src->bytes_in_buffer -= bytes;
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}
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}
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static boolean sk_fill_mem_input_buffer (j_decompress_ptr cinfo) {
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/* The whole JPEG data is expected to reside in the supplied memory,
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* buffer, so any request for more data beyond the given buffer size
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* is treated as an error.
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*/
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return false;
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}
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/*
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* Constructor for the source manager that we provide to libjpeg
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* We provide skia implementations of all of the stream processing functions required by libjpeg
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*/
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skjpeg_source_mgr::skjpeg_source_mgr(SkStream* stream)
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: fStream(stream)
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{
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if (stream->hasLength() && stream->getMemoryBase()) {
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init_source = sk_init_mem_source;
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fill_input_buffer = sk_fill_mem_input_buffer;
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skip_input_data = sk_skip_mem_input_data;
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resync_to_restart = jpeg_resync_to_restart;
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term_source = sk_term_source;
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bytes_in_buffer = static_cast<size_t>(stream->getLength());
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next_input_byte = static_cast<const JOCTET*>(stream->getMemoryBase());
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} else {
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init_source = sk_init_buffered_source;
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fill_input_buffer = sk_fill_buffered_input_buffer;
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skip_input_data = sk_skip_buffered_input_data;
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resync_to_restart = jpeg_resync_to_restart;
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term_source = sk_term_source;
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}
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}
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