Make SkSHA1 and SkM5 use common SkDigestHash result type

src/utils/SkBitmapTransformer.cpp

Index: src/utils/SkBitmapTransformer.cpp
===================================================================
--- src/utils/SkBitmapTransformer.cpp	(revision 8685)
+++ src/utils/SkBitmapTransformer.cpp	(working copy)
@@ -85,3 +85,30 @@
     fBitmap.unlockPixels();
     return true;
 }
+
+bool SkBitmapTransformer::copyRowToPixelBuffer(int row, void *dstBuffer,
+                                               size_t dstBufferSize) const {
+    if (!this->isValid(true)) {
+        return false;
+    }
+    if ((row < 0) || (row >= this->numRows())) {
+        // EPOGER: add unit test for this check
+        SkDEBUGF(("row %d must be within range [0,%d]\n", row, numRows()-1));
+        return false;
+    }
+    size_t bytesNeeded = this->bytesNeededPerRow();
+    if (dstBufferSize < bytesNeeded) {
+        SkDEBUGF(("dstBufferSize %d must be >= %d\n", dstBufferSize, bytesNeeded));
+        return false;
+    }
+
+    fBitmap.lockPixels();

[bungeman-skia, 2013/04/22 05:14:02]

This isn't cheap as it involves taking a mutex, as does the unlock. This is also
taken care of with the ARGB encoder as it just does the one lock/unlock. If you
take this lock/unlock out of here and push it up to just one lock/unlock in the
hasher, what does that do?

+    int width = fBitmap.width();
+    size_t srcRowBytes = fBitmap.rowBytes();
+    const char *srcBytes = const_cast<const char *>(static_cast<char*>(fBitmap.getPixels()));
+    char *dstBytes = static_cast<char *>(dstBuffer);
+    srcBytes += srcRowBytes * row;
+    transform_scanline(srcBytes, width, dstBytes);
+    fBitmap.unlockPixels();
+    return true;
+}