1/*
2 * Copyright 2015 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#include "src/codec/SkJpegUtility.h"
9
10#include "include/core/SkStream.h"
11#include "include/core/SkTypes.h"
12#include "include/private/base/SkTArray.h"
13#include "src/codec/SkCodecPriv.h"
14#include "src/codec/SkJpegPriv.h"
15
16#include <csetjmp>
17#include <cstddef>
18
19extern "C" {
20 #include "jmorecfg.h"
21 #include "jpeglib.h"
22}
23
24/*
25 * Call longjmp to continue execution on an error
26 */
27void skjpeg_err_exit(j_common_ptr dinfo) {
28 // Simply return to Skia client code
29 // JpegDecoderMgr will take care of freeing memory
30 skjpeg_error_mgr* error = (skjpeg_error_mgr*) dinfo->err;
31 (*error->output_message) (dinfo);
32 if (error->fJmpBufStack.empty()) {
33 SK_ABORT("JPEG error with no jmp_buf set.");
34 }
35 longjmp(env: *error->fJmpBufStack.back(), val: 1);
36}
37
38// Functions for buffered sources //
39
40/*
41 * Initialize the buffered source manager
42 */
43static void sk_init_buffered_source(j_decompress_ptr dinfo) {
44 skjpeg_source_mgr* src = (skjpeg_source_mgr*) dinfo->src;
45 src->next_input_byte = (const JOCTET*) src->fBuffer;
46 src->bytes_in_buffer = 0;
47}
48
49/*
50 * Fill the input buffer from the stream
51 */
52static boolean sk_fill_buffered_input_buffer(j_decompress_ptr dinfo) {
53 skjpeg_source_mgr* src = (skjpeg_source_mgr*) dinfo->src;
54 size_t bytes = src->fStream->read(buffer: src->fBuffer, size: skjpeg_source_mgr::kBufferSize);
55
56 // libjpeg is still happy with a less than full read, as long as the result is non-zero
57 if (bytes == 0) {
58 // Let libjpeg know that the buffer needs to be refilled
59 src->next_input_byte = nullptr;
60 src->bytes_in_buffer = 0;
61 return false;
62 }
63
64 src->next_input_byte = (const JOCTET*) src->fBuffer;
65 src->bytes_in_buffer = bytes;
66 return true;
67}
68
69/*
70 * Skip a certain number of bytes in the stream
71 */
72static void sk_skip_buffered_input_data(j_decompress_ptr dinfo, long numBytes) {
73 skjpeg_source_mgr* src = (skjpeg_source_mgr*) dinfo->src;
74 size_t bytes = (size_t) numBytes;
75
76 if (bytes > src->bytes_in_buffer) {
77 size_t bytesToSkip = bytes - src->bytes_in_buffer;
78 if (bytesToSkip != src->fStream->skip(size: bytesToSkip)) {
79 SkCodecPrintf("Failure to skip.\n");
80 dinfo->err->error_exit((j_common_ptr) dinfo);
81 return;
82 }
83
84 src->next_input_byte = (const JOCTET*) src->fBuffer;
85 src->bytes_in_buffer = 0;
86 } else {
87 src->next_input_byte += numBytes;
88 src->bytes_in_buffer -= numBytes;
89 }
90}
91
92/*
93 * We do not need to do anything to terminate our stream
94 */
95static void sk_term_source(j_decompress_ptr dinfo)
96{
97 // The current implementation of SkJpegCodec does not call
98 // jpeg_finish_decompress(), so this function is never called.
99 // If we want to modify this function to do something, we also
100 // need to modify SkJpegCodec to call jpeg_finish_decompress().
101}
102
103// Functions for memory backed sources //
104
105/*
106 * Initialize the mem backed source manager
107 */
108static void sk_init_mem_source(j_decompress_ptr dinfo) {
109 /* no work necessary here, all things are done in constructor */
110}
111
112static void sk_skip_mem_input_data (j_decompress_ptr cinfo, long num_bytes) {
113 jpeg_source_mgr* src = cinfo->src;
114 size_t bytes = static_cast<size_t>(num_bytes);
115 if(bytes > src->bytes_in_buffer) {
116 src->next_input_byte = nullptr;
117 src->bytes_in_buffer = 0;
118 } else {
119 src->next_input_byte += bytes;
120 src->bytes_in_buffer -= bytes;
121 }
122}
123
124static boolean sk_fill_mem_input_buffer (j_decompress_ptr cinfo) {
125 /* The whole JPEG data is expected to reside in the supplied memory,
126 * buffer, so any request for more data beyond the given buffer size
127 * is treated as an error.
128 */
129 return false;
130}
131
132/*
133 * Constructor for the source manager that we provide to libjpeg
134 * We provide skia implementations of all of the stream processing functions required by libjpeg
135 */
136skjpeg_source_mgr::skjpeg_source_mgr(SkStream* stream)
137 : fStream(stream)
138{
139 if (stream->hasLength() && stream->getMemoryBase()) {
140 init_source = sk_init_mem_source;
141 fill_input_buffer = sk_fill_mem_input_buffer;
142 skip_input_data = sk_skip_mem_input_data;
143 resync_to_restart = jpeg_resync_to_restart;
144 term_source = sk_term_source;
145 bytes_in_buffer = static_cast<size_t>(stream->getLength());
146 next_input_byte = static_cast<const JOCTET*>(stream->getMemoryBase());
147 } else {
148 init_source = sk_init_buffered_source;
149 fill_input_buffer = sk_fill_buffered_input_buffer;
150 skip_input_data = sk_skip_buffered_input_data;
151 resync_to_restart = jpeg_resync_to_restart;
152 term_source = sk_term_source;
153 }
154}
155

source code of flutter_engine/third_party/skia/src/codec/SkJpegUtility.cpp