diff -r 000000000000 -r 6474c204b198 gfx/skia/trunk/src/images/SkDecodingImageGenerator.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gfx/skia/trunk/src/images/SkDecodingImageGenerator.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,256 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkData.h"
+#include "SkDecodingImageGenerator.h"
+#include "SkImageDecoder.h"
+#include "SkImageInfo.h"
+#include "SkImageGenerator.h"
+#include "SkImagePriv.h"
+#include "SkStream.h"
+#include "SkUtils.h"
+
+static bool equal_modulo_alpha(const SkImageInfo& a, const SkImageInfo& b) {
+    return a.width() == b.width() && a.height() == b.height() &&
+           a.colorType() == b.colorType();
+}
+
+namespace {
+/**
+ *  Special allocator used by getPixels(). Uses preallocated memory
+ *  provided if possible, else fall-back on the default allocator
+ */
+class TargetAllocator : public SkBitmap::Allocator {
+public:
+    TargetAllocator(const SkImageInfo& info,
+                    void* target,
+                    size_t rowBytes)
+        : fInfo(info)
+        , fTarget(target)
+        , fRowBytes(rowBytes)
+    {}
+
+    bool isReady() { return (fTarget != NULL); }
+
+    virtual bool allocPixelRef(SkBitmap* bm, SkColorTable* ct) {
+        if (NULL == fTarget || !equal_modulo_alpha(fInfo, bm->info())) {
+            // Call default allocator.
+            return bm->allocPixels(NULL, ct);
+        }
+
+        // TODO(halcanary): verify that all callers of this function
+        // will respect new RowBytes.  Will be moot once rowbytes belongs
+        // to PixelRef.
+        bm->installPixels(fInfo, fTarget, fRowBytes, NULL, NULL);
+
+        fTarget = NULL;  // never alloc same pixels twice!
+        return true;
+    }
+
+private:
+    const SkImageInfo fInfo;
+    void* fTarget;  // Block of memory to be supplied as pixel memory
+                    // in allocPixelRef.  Must be large enough to hold
+                    // a bitmap described by fInfo and fRowBytes
+    const size_t fRowBytes;  // rowbytes for the destination bitmap
+
+    typedef SkBitmap::Allocator INHERITED;
+};
+
+// TODO(halcanary): Give this macro a better name and move it into SkTypes.h
+#ifdef SK_DEBUG
+    #define SkCheckResult(expr, value)  SkASSERT((value) == (expr))
+#else
+    #define SkCheckResult(expr, value)  (void)(expr)
+#endif
+
+#ifdef SK_DEBUG
+inline bool check_alpha(SkAlphaType reported, SkAlphaType actual) {
+    return ((reported == actual)
+            || ((reported == kPremul_SkAlphaType)
+                && (actual == kOpaque_SkAlphaType)));
+}
+#endif  // SK_DEBUG
+
+}  // namespace
+////////////////////////////////////////////////////////////////////////////////
+
+SkDecodingImageGenerator::SkDecodingImageGenerator(
+        SkData* data,
+        SkStreamRewindable* stream,
+        const SkImageInfo& info,
+        int sampleSize,
+        bool ditherImage)
+    : fData(data)
+    , fStream(stream)
+    , fInfo(info)
+    , fSampleSize(sampleSize)
+    , fDitherImage(ditherImage)
+{
+    SkASSERT(stream != NULL);
+    SkSafeRef(fData);  // may be NULL.
+}
+
+SkDecodingImageGenerator::~SkDecodingImageGenerator() {
+    SkSafeUnref(fData);
+    fStream->unref();
+}
+
+bool SkDecodingImageGenerator::getInfo(SkImageInfo* info) {
+    if (info != NULL) {
+        *info = fInfo;
+    }
+    return true;
+}
+
+SkData* SkDecodingImageGenerator::refEncodedData() {
+    // This functionality is used in `gm --serialize`
+    // Does not encode options.
+    if (fData != NULL) {
+        return SkSafeRef(fData);
+    }
+    // TODO(halcanary): SkStreamRewindable needs a refData() function
+    // which returns a cheap copy of the underlying data.
+    if (!fStream->rewind()) {
+        return NULL;
+    }
+    size_t length = fStream->getLength();
+    if (0 == length) {
+        return NULL;
+    }
+    void* buffer = sk_malloc_flags(length, 0);
+    SkCheckResult(fStream->read(buffer, length), length);
+    fData = SkData::NewFromMalloc(buffer, length);
+    return SkSafeRef(fData);
+}
+
+bool SkDecodingImageGenerator::getPixels(const SkImageInfo& info,
+                                         void* pixels,
+                                         size_t rowBytes) {
+    if (NULL == pixels) {
+        return false;
+    }
+    if (fInfo != info) {
+        // The caller has specified a different info.  This is an
+        // error for this kind of SkImageGenerator.  Use the Options
+        // to change the settings.
+        return false;
+    }
+    if (info.minRowBytes() > rowBytes) {
+        // The caller has specified a bad rowBytes.
+        return false;
+    }
+
+    SkAssertResult(fStream->rewind());
+    SkAutoTDelete<SkImageDecoder> decoder(SkImageDecoder::Factory(fStream));
+    if (NULL == decoder.get()) {
+        return false;
+    }
+    decoder->setDitherImage(fDitherImage);
+    decoder->setSampleSize(fSampleSize);
+
+    SkBitmap bitmap;
+    TargetAllocator allocator(fInfo, pixels, rowBytes);
+    decoder->setAllocator(&allocator);
+    // TODO: need to be able to pass colortype directly to decoder
+    SkBitmap::Config legacyConfig = SkColorTypeToBitmapConfig(info.colorType());
+    bool success = decoder->decode(fStream, &bitmap, legacyConfig,
+                                   SkImageDecoder::kDecodePixels_Mode);
+    decoder->setAllocator(NULL);
+    if (!success) {
+        return false;
+    }
+    if (allocator.isReady()) {  // Did not use pixels!
+        SkBitmap bm;
+        SkASSERT(bitmap.canCopyTo(info.colorType()));
+        bool copySuccess = bitmap.copyTo(&bm, info.colorType(), &allocator);
+        if (!copySuccess || allocator.isReady()) {
+            SkDEBUGFAIL("bitmap.copyTo(requestedConfig) failed.");
+            // Earlier we checked canCopyto(); we expect consistency.
+            return false;
+        }
+        SkASSERT(check_alpha(info.alphaType(), bm.alphaType()));
+    } else {
+        SkASSERT(check_alpha(info.alphaType(), bitmap.alphaType()));
+    }
+    return true;
+}
+
+SkImageGenerator* SkDecodingImageGenerator::Create(
+        SkData* data,
+        const SkDecodingImageGenerator::Options& opts) {
+    SkASSERT(data != NULL);
+    if (NULL == data) {
+        return NULL;
+    }
+    SkStreamRewindable* stream = SkNEW_ARGS(SkMemoryStream, (data));
+    SkASSERT(stream != NULL);
+    SkASSERT(stream->unique());
+    return SkDecodingImageGenerator::Create(data, stream, opts);
+}
+
+SkImageGenerator* SkDecodingImageGenerator::Create(
+        SkStreamRewindable* stream,
+        const SkDecodingImageGenerator::Options& opts) {
+    SkASSERT(stream != NULL);
+    SkASSERT(stream->unique());
+    if ((stream == NULL) || !stream->unique()) {
+        SkSafeUnref(stream);
+        return NULL;
+    }
+    return SkDecodingImageGenerator::Create(NULL, stream, opts);
+}
+
+// A contructor-type function that returns NULL on failure.  This
+// prevents the returned SkImageGenerator from ever being in a bad
+// state.  Called by both Create() functions
+SkImageGenerator* SkDecodingImageGenerator::Create(
+        SkData* data,
+        SkStreamRewindable* stream,
+        const SkDecodingImageGenerator::Options& opts) {
+    SkASSERT(stream);
+    SkAutoTUnref<SkStreamRewindable> autoStream(stream);  // always unref this.
+    if (opts.fUseRequestedColorType &&
+        (kIndex_8_SkColorType == opts.fRequestedColorType)) {
+        // We do not support indexed color with SkImageGenerators,
+        return NULL;
+    }
+    SkAssertResult(autoStream->rewind());
+    SkAutoTDelete<SkImageDecoder> decoder(SkImageDecoder::Factory(autoStream));
+    if (NULL == decoder.get()) {
+        return NULL;
+    }
+    SkBitmap bitmap;
+    decoder->setSampleSize(opts.fSampleSize);
+    if (!decoder->decode(stream, &bitmap,
+                         SkImageDecoder::kDecodeBounds_Mode)) {
+        return NULL;
+    }
+    if (bitmap.config() == SkBitmap::kNo_Config) {
+        return NULL;
+    }
+
+    SkImageInfo info = bitmap.info();
+
+    if (!opts.fUseRequestedColorType) {
+        // Use default
+        if (kIndex_8_SkColorType == bitmap.colorType()) {
+            // We don't support kIndex8 because we don't support
+            // colortables in this workflow.
+            info.fColorType = kPMColor_SkColorType;
+        }
+    } else {
+        if (!bitmap.canCopyTo(opts.fRequestedColorType)) {
+            SkASSERT(bitmap.colorType() != opts.fRequestedColorType);
+            return NULL;  // Can not translate to needed config.
+        }
+        info.fColorType = opts.fRequestedColorType;
+    }
+    return SkNEW_ARGS(SkDecodingImageGenerator,
+                      (data, autoStream.detach(), info,
+                       opts.fSampleSize, opts.fDitherImage));
+}