Create a scanline decoder without creating a codec

src/codec/SkScanlineDecoder.cpp

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkScanlineDecoder.h"
+#include "SkCodec_libpng.h"
+#include "SkCodecPriv.h"
+#ifndef SK_BUILD_FOR_ANDROID_FRAMEWORK
+#include "SkJpegCodec.h"
+#endif
+
+struct DecoderProc {
+    bool (*IsFormat)(SkStream*);
+    SkScanlineDecoder* (*NewFromStream)(SkStream*);
+};
+
+static const DecoderProc gDecoderProcs[] = {
+    { SkPngCodec::IsPng, SkPngCodec::NewSDFromStream },
+#ifndef SK_BUILD_FOR_ANDROID_FRAMEWORK
+    { SkJpegCodec::IsJpeg, SkJpegCodec::NewSDFromStream },
+#endif
+};
+
+SkScanlineDecoder* SkScanlineDecoder::NewFromStream(SkStream* stream) {
+    if (!stream) {
+        return NULL;
+    }
+
+    SkAutoTDelete<SkStream> streamDeleter(stream);
+
+    SkAutoTDelete<SkScanlineDecoder> codec(NULL);
+    for (uint32_t i = 0; i < SK_ARRAY_COUNT(gDecoderProcs); i++) {
+        DecoderProc proc = gDecoderProcs[i];
+        const bool correctFormat = proc.IsFormat(stream);
+        if (!stream->rewind()) {
+            return NULL;
+        }
+        if (correctFormat) {
+            codec.reset(proc.NewFromStream(streamDeleter.detach()));
+            break;
+        }
+    }
+
+    // Set the max size at 128 megapixels (512 MB for kN32).
+    // This is about 4x smaller than a test image that takes a few minutes for
+    // dm to decode and draw.
+    const int32_t maxSize = 1 << 27;
+    if (codec && codec->getInfo().width() * codec->getInfo().height() > maxSize) {
+        SkCodecPrintf("Error: Image size too large, cannot decode.\n");
+        return NULL;
+    } else {
+        return codec.detach();
+    }
+}
+
+SkScanlineDecoder* SkScanlineDecoder::NewFromData(SkData* data) {
+    if (!data) {
+        return NULL;
+    }
+    return NewFromStream(SkNEW_ARGS(SkMemoryStream, (data)));
+}
+
+
+SkCodec::Result SkScanlineDecoder::start(const SkImageInfo& dstInfo,
+        const SkCodec::Options* options, SkPMColor ctable[], int* ctableCount) {
+    // Set options.
+    SkCodec::Options optsStorage;
+    if (NULL == options) {
+        options = &optsStorage;
+    }
+
+    const SkCodec::Result result = this->onStart(dstInfo, *options, ctable, ctableCount);
+    if (result != SkCodec::kSuccess) {
+        return result;
+    }
+
+    fCurrScanline = 0;
+    fDstInfo = dstInfo;
+    return SkCodec::kSuccess;
+}
+
+SkCodec::Result SkScanlineDecoder::start(const SkImageInfo& dstInfo) {
+    SkASSERT(kIndex_8_SkColorType != dstInfo.colorType());
+    if (kIndex_8_SkColorType == dstInfo.colorType()) {
+        return SkCodec::kInvalidConversion;
+    }
+    return this->start(dstInfo, NULL, NULL, NULL);
+}
+