Make SkSHA1 and SkM5 use common SkDigestHash result type

src/utils/SkBitmapHasher.cpp

Index: src/utils/SkBitmapHasher.cpp
===================================================================
--- src/utils/SkBitmapHasher.cpp	(revision 8685)
+++ src/utils/SkBitmapHasher.cpp	(working copy)
@@ -11,12 +11,12 @@
 #include "SkBitmapTransformer.h"
 #include "SkCityHash.h"
 #include "SkEndian.h"
+#include "SkMD5.h"
 
 /**
- * Write an integer value into a bytebuffer in little-endian order.
+ * Write an int32_t value into a bytebuffer in little-endian order.
  */
-static void write_int_to_buffer(int val, char* buf) {
-    val = SkEndian_SwapLE32(val);
+static void write_int32_to_buffer(int32_t val, char* buf) {
     for (int byte=0; byte<4; byte++) {
         *buf++ = (char)(val & 0xff);
         val = val >> 8;
@@ -24,7 +24,7 @@
 }
 
 /*static*/ bool SkBitmapHasher::ComputeDigestInternal(
-        const SkBitmap& bitmap, const SkBitmapTransformer& transformer, SkHashDigest *result) {
+        const SkBitmap& bitmap, const SkBitmapTransformer& transformer, BITMAP_HASH_TYPE *result) {
     size_t pixelBufferSize = transformer.bytesNeededTotal();
     size_t totalBufferSize = pixelBufferSize + 8; // leave room for x/y dimensions
 
@@ -32,20 +32,32 @@
     char *bufferStart = static_cast<char *>(bufferManager.get());
     char *bufPtr = bufferStart;
     // start with the x/y dimensions
-    write_int_to_buffer(bitmap.width(), bufPtr);
+    write_int32_to_buffer(bitmap.width(), bufPtr);
     bufPtr += 4;
-    write_int_to_buffer(bitmap.height(), bufPtr);
+    write_int32_to_buffer(bitmap.height(), bufPtr);
     bufPtr += 4;
 
     // add all the pixel data
+    // EPOGER: if we are using our MD5 or SHA1 implementations, we can add this
+    // data to the hash algorithm in-place (without the big memcpy).
+    // Add that optimization!
     if (!transformer.copyBitmapToPixelBuffer(bufPtr, pixelBufferSize)) {
         return false;
     }
+#ifdef BITMAP_HASH_TYPE_SkHashDigest
+    SkMD5 hasher;
+    hasher.update(reinterpret_cast<const uint8_t*>(bufferStart), totalBufferSize);
+    SkMD5::Digest digest;

[epoger, 2013/04/19 17:20:53]

In patchset 11, I have reverted all changes to SkMD5 and SkSHA1 code.

Instead, similar to Ben's suggestion in
https://codereview.chromium.org/14265010/#msg5 , I leave the SkMD5 interface
as-is and now SkBitmapHasher.cpp wraps its result in an SkHashDigest object.

For now, there is still an extra copy of the hash digest created on the stack
here in SkBitmapHasher::ComputeDigestInternal(); I'll see if I can eliminate
that with a malloc here.  But for now, I wanted to make as simple a change as
possible that would revert the changes to SkMD5 and SkSHA1.

Ben... do you think I'm on the right track here?

+    hasher.finish(digest);
+    // EPOGER: instead of creating the extra copy on the stack and running copyFrom, use malloc and then just make the SkHashDigest hold a reference to it?
+    result->copyFrom(&digest, sizeof(digest));
+#else
     *result = SkCityHash::Compute64(bufferStart, totalBufferSize);
+#endif
     return true;
 }
 
-/*static*/ bool SkBitmapHasher::ComputeDigest(const SkBitmap& bitmap, SkHashDigest *result) {
+/*static*/ bool SkBitmapHasher::ComputeDigest(const SkBitmap& bitmap, BITMAP_HASH_TYPE *result) {
     const SkBitmapTransformer::PixelFormat kPixelFormat =
         SkBitmapTransformer::kARGB_8888_Premul_PixelFormat;