1 /*
2  * Copyright 2013 The Android Open Source Project
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 "SkErrorInternals.h"
9 #include "SkImageDecoder.h"
10 #include "SkStream.h"
11 #include "SkTRegistry.h"
12 
13 // This file is used for registration of SkImageDecoders. It also holds a function
14 // for checking all the the registered SkImageDecoders for one that matches an
15 // input SkStreamRewindable.
16 
17 template SkImageDecoder_DecodeReg* SkImageDecoder_DecodeReg::gHead;
18 
19 SkImageDecoder* image_decoder_from_stream(SkStreamRewindable*);
20 
image_decoder_from_stream(SkStreamRewindable * stream)21 SkImageDecoder* image_decoder_from_stream(SkStreamRewindable* stream) {
22     SkImageDecoder* codec = nullptr;
23     const SkImageDecoder_DecodeReg* curr = SkImageDecoder_DecodeReg::Head();
24     while (curr) {
25         codec = curr->factory()(stream);
26         // we rewind here, because we promise later when we call "decode", that
27         // the stream will be at its beginning.
28         bool rewindSuceeded = stream->rewind();
29 
30         // our image decoder's require that rewind is supported so we fail early
31         // if we are given a stream that does not support rewinding.
32         if (!rewindSuceeded) {
33             SkDEBUGF(("Unable to rewind the image stream."));
34             delete codec;
35             return nullptr;
36         }
37 
38         if (codec) {
39             return codec;
40         }
41         curr = curr->next();
42     }
43     return nullptr;
44 }
45 
46 template SkImageDecoder_FormatReg* SkImageDecoder_FormatReg::gHead;
47 
GetStreamFormat(SkStreamRewindable * stream)48 SkImageDecoder::Format SkImageDecoder::GetStreamFormat(SkStreamRewindable* stream) {
49     const SkImageDecoder_FormatReg* curr = SkImageDecoder_FormatReg::Head();
50     while (curr != nullptr) {
51         Format format = curr->factory()(stream);
52         if (!stream->rewind()) {
53             SkErrorInternals::SetError(kInvalidOperation_SkError,
54                                        "Unable to rewind the image stream\n");
55             return kUnknown_Format;
56         }
57         if (format != kUnknown_Format) {
58             return format;
59         }
60         curr = curr->next();
61     }
62     return kUnknown_Format;
63 }
64