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