Split SkBmpCodec into three separate classes

src/codec/SkBmpMaskCodec.cpp

Index: src/codec/SkBmpMaskCodec.cpp
diff --git a/src/codec/SkBmpMaskCodec.cpp b/src/codec/SkBmpMaskCodec.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..6b6fcf4cba13492ae3ac10693afa8c104d9a6808
--- /dev/null
+++ b/src/codec/SkBmpMaskCodec.cpp
@@ -0,0 +1,140 @@
+/*
+ * 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 "SkBmpMaskCodec.h"
+#include "SkCodecPriv.h"
+#include "SkColorPriv.h"
+
+/*
+ * Checks if the conversion between the input image and the requested output
+ * image has been implemented
+ */
+static bool conversion_possible(const SkImageInfo& dst,
+                                const SkImageInfo& src) {
+    // Ensure that the profile type is unchanged
+    if (dst.profileType() != src.profileType()) {
+        return false;
+    }
+
+    // Ensure the alpha type is valid
+    if (!valid_alpha(dst.alphaType(), src.alphaType())) {
+        return false;
+    }
+
+    // Check for supported color types
+    switch (dst.colorType()) {
+        // Allow output to kN32
+        case kN32_SkColorType:
+            return true;
+        default:
+            return false;
+    }
+}
+
+
+/*
+ * Creates an instance of the decoder
+ */
+SkBmpMaskCodec::SkBmpMaskCodec(const SkImageInfo& info, SkStream* stream,
+                               uint16_t bitsPerPixel, SkMasks* masks,
+                               SkBmpCodec::RowOrder rowOrder)
+    : INHERITED(info, stream, bitsPerPixel, rowOrder)
+    , fMasks(masks)
+    , fMaskSwizzler(NULL)
+    , fSrcBuffer(NULL)
+{}
+
+/*
+ * Initiates the bitmap decode
+ */
+SkCodec::Result SkBmpMaskCodec::onGetPixels(const SkImageInfo& dstInfo,
+                                            void* dst, size_t dstRowBytes,
+                                            const Options& opts,
+                                            SkPMColor* inputColorPtr,
+                                            int* inputColorCount) {
+    if (!this->handleRewind(false)) {
+        return kCouldNotRewind;
+    }
+    if (opts.fSubset) {
+        // Subsets are not supported.
+        return kUnimplemented;
+    }
+    if (dstInfo.dimensions() != this->getInfo().dimensions()) {
+        SkCodecPrintf("Error: scaling not supported.\n");
+        return kInvalidScale;
+    }
+
+    if (!conversion_possible(dstInfo, this->getInfo())) {
+        SkCodecPrintf("Error: cannot convert input type to output type.\n");
+        return kInvalidConversion;
+    }
+
+    // Initialize a the mask swizzler
+    if (!this->initializeSwizzler(dstInfo)) {
+        SkCodecPrintf("Error: cannot initialize swizzler.\n");
+        return kInvalidConversion;
+    }
+
+    // Perform the decode
+    SkCodec::Result result = decode(dstInfo, dst, dstRowBytes, opts);

[scroggo, 2015/08/06 21:12:41]

nit: This can be simplified (also it should have a this pointer):

    return this->decode(...);

[msarett, 2015/08/06 21:41:42]

Done.

+
+    return result;
+}
+
+bool SkBmpMaskCodec::initializeSwizzler(const SkImageInfo& dstInfo) {
+    // Allocate space for a row buffer
+    const size_t rowBytes = SkAlign4(compute_row_bytes(dstInfo.width(), this->bitsPerPixel()));
+    fSrcBuffer.reset(SkNEW_ARRAY(uint8_t, rowBytes));
+
+    // Create the swizzler
+    fMaskSwizzler.reset(SkMaskSwizzler::CreateMaskSwizzler(
+            dstInfo, fMasks, this->bitsPerPixel()));
+
+    if (NULL == fMaskSwizzler.get()) {
+        return false;
+    }
+
+    return true;
+}
+
+/*
+ * Performs the decoding
+ */
+SkCodec::Result SkBmpMaskCodec::decode(const SkImageInfo& dstInfo,
+                                       void* dst, size_t dstRowBytes,
+                                       const Options& opts) {
+    // Set constant values
+    const int width = dstInfo.width();
+    const int height = dstInfo.height();
+    const size_t rowBytes = SkAlign4(compute_row_bytes(width, this->bitsPerPixel()));
+
+    // Iterate over rows of the image
+    uint8_t* srcRow = fSrcBuffer.get();
+    for (int y = 0; y < height; y++) {
+        // Read a row of the input
+        if (this->stream()->read(srcRow, rowBytes) != rowBytes) {

[scroggo, 2015/08/06 21:12:41]

Doesn't need to be a part of this patch set, but I think this can become a
readRow function, which can be shared with the scanline decoder, like wbmp.

[msarett, 2015/08/06 21:41:42]

Acknowledged.

+            SkCodecPrintf("Warning: incomplete input stream.\n");
+            // Fill the destination image on failure
+            SkPMColor fillColor = dstInfo.alphaType() == kOpaque_SkAlphaType ?
+                    SK_ColorBLACK : SK_ColorTRANSPARENT;
+            if (kNo_ZeroInitialized == opts.fZeroInitialized || 0 != fillColor) {
+                void* dstStart = this->getDstStartRow(dst, dstRowBytes, y);
+                SkSwizzler::Fill(dstStart, dstInfo, dstRowBytes, dstInfo.height() - y, fillColor,
+                        NULL);
+            }
+            return kIncompleteInput;
+        }
+
+        // Decode the row in destination format
+        int row = SkBmpCodec::kBottomUp_RowOrder == this->rowOrder() ? height - 1 - y : y;
+        void* dstRow = SkTAddOffset<void>(dst, row * dstRowBytes);
+        fMaskSwizzler->swizzle(dstRow, srcRow);
+    }
+
+    // Finished decoding the entire image
+    return kSuccess;
+}