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      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 
     21 SkImageDecoder* image_decoder_from_stream(SkStreamRewindable* stream) {
     22     SkImageDecoder* codec = NULL;
     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             SkDELETE(codec);
     35             return NULL;
     36         }
     37 
     38         if (codec) {
     39             return codec;
     40         }
     41         curr = curr->next();
     42     }
     43     return NULL;
     44 }
     45 
     46 template SkImageDecoder_FormatReg* SkImageDecoder_FormatReg::gHead;
     47 
     48 SkImageDecoder::Format SkImageDecoder::GetStreamFormat(SkStreamRewindable* stream) {
     49     const SkImageDecoder_FormatReg* curr = SkImageDecoder_FormatReg::Head();
     50     while (curr != NULL) {
     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