Make SkSHA1 and SkM5 use common SkDigestHash result type

src/utils/SkMD5.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  *
  * The following code is based on the description in RFC 1321.
  * http://www.ietf.org/rfc/rfc1321.txt
  */
 
@@ skipping 42 matching lines @@
         bufferIndex = 0;
     } else {
         inputIndex = 0;
     }
 
     memcpy(&this->buffer[bufferIndex], &input[inputIndex], inputLength - inputIndex);
 
     this->byteCount += inputLength;
 }
 
-void SkMD5::finish(Digest& digest) {
+void SkMD5::finish(SkHashDigest& digest) {
     // Get the number of bits before padding.
     uint8_t bits[8];
     encode(bits, this->byteCount << 3);
 
     // Pad out to 56 mod 64.
     unsigned int bufferIndex = (unsigned int)(this->byteCount & 0x3F);
     unsigned int paddingLength = (bufferIndex < 56) ? (56 - bufferIndex) : (120 - bufferIndex);
     static uint8_t PADDING[64] = {
         0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
     };
     this->update(PADDING, paddingLength);
 
     // Append length (length before padding, will cause final update).
     this->update(bits, 8);
 
     // Write out digest.
-    encode(digest.data, this->state);
+    // TODO(epoger): eliminate the extra 16-byte copy, by writing directly into digest.data???

[epoger, 2013/04/15 18:21:38]

Any thoughts on this?  I intend to get to work on this while awaiting review of
the rest of this change...

+    // NO, we can't do that, because digest.data is immutable (wrapped in SkData).
+    // Or:
+    //  1. malloc 16 bytes here (wrapped in an SkData object),
+    //  2. write the digest into the SkData-wrapped 16 bytes,
+    //  3. bump the ref counter on that SkData-wrapped 16 bytes,
+    //  4. replace digest's fSkDataPtr with the new one
+    size_t digestSize = 16;
+    uint8_t tempDigestData[digestSize];
+    encode(tempDigestData, this->state);
+    digest.set(tempDigestData, digestSize);
 
 #if defined(SK_MD5_CLEAR_DATA)
     // Clear state.
     memset(this, 0, sizeof(*this));
 #endif
 }
 
 struct F { uint32_t operator()(uint32_t x, uint32_t y, uint32_t z) {
     //return (x & y) | ((~x) & z);
-    return ((y ^ z) & x) ^ z; //equivelent but faster
+    return ((y ^ z) & x) ^ z; //equivalent but faster
 }};
 
 struct G { uint32_t operator()(uint32_t x, uint32_t y, uint32_t z) {
     return (x & z) | (y & (~z));
-    //return ((x ^ y) & z) ^ y; //equivelent but slower
+    //return ((x ^ y) & z) ^ y; //equivalent but slower
 }};
 
 struct H { uint32_t operator()(uint32_t x, uint32_t y, uint32_t z) {
     return x ^ y ^ z;
 }};
 
 struct I { uint32_t operator()(uint32_t x, uint32_t y, uint32_t z) {
     return y ^ (x | (~z));
 }};
 
@@ skipping 134 matching lines @@
 #endif
     for (size_t i = 0, j = 0; j < 64; i++, j += 4) {
         storage[i] =  ((uint32_t)input[j  ])        |
                      (((uint32_t)input[j+1]) <<  8) |
                      (((uint32_t)input[j+2]) << 16) |
                      (((uint32_t)input[j+3]) << 24);
     }
     return storage;
 #endif
 }