Allow creating multiple scanline decoders.

tests/CodexTest.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 "Resources.h"
 #include "SkBitmap.h"
 #include "SkCodec.h"
@@ skipping 10 matching lines @@
     SkAutoLockPixels autoLockPixels(bm);
     SkASSERT(bm.getPixels());
     SkMD5 md5;
     size_t rowLen = bm.info().bytesPerPixel() * bm.width();
     for (int y = 0; y < bm.height(); ++y) {
         md5.update(static_cast<uint8_t*>(bm.getAddr(0, y)), rowLen);
     }
     md5.finish(*digest);
 }
 
+/**
+ *  Compute the digest for bm and compare it to a known good digest.
+ *  @param r Reporter to assert that bm's digest matches goodDigest.
+ *  @param goodDigest The known good digest to compare to.
+ *  @param bm The bitmap to test.
+ */
+static void compare_to_good_digest(skiatest::Reporter* r, const SkMD5::Digest& goodDigest,
+                           const SkBitmap& bm) {
+    SkMD5::Digest digest;
+    md5(bm, &digest);
+    REPORTER_ASSERT(r, digest == goodDigest);
+}
+
 static void check(skiatest::Reporter* r,
                   const char path[],
                   SkISize size,
                   bool supportsScanlineDecoding) {
     SkAutoTDelete<SkStream> stream(resource(path));
     if (!stream) {
         SkDebugf("Missing resource '%s'\n", path);
         return;
     }
     SkAutoTDelete<SkCodec> codec(SkCodec::NewFromStream(stream.detach()));
     if (!codec) {
         ERRORF(r, "Unable to decode '%s'", path);
         return;
     }
 
     // This test is used primarily to verify rewinding works properly.  Using kN32 allows
     // us to test this without the added overhead of creating different bitmaps depending
     // on the color type (ex: building a color table for kIndex8).  DM is where we test
     // decodes to all possible destination color types.
     SkImageInfo info = codec->getInfo().makeColorType(kN32_SkColorType);
     REPORTER_ASSERT(r, info.dimensions() == size);
     SkBitmap bm;
     bm.allocPixels(info);
     SkAutoLockPixels autoLockPixels(bm);
     SkCodec::Result result =
         codec->getPixels(info, bm.getPixels(), bm.rowBytes(), NULL, NULL, NULL);
     REPORTER_ASSERT(r, result == SkCodec::kSuccess);
 
-    SkMD5::Digest digest1, digest2;
-    md5(bm, &digest1);
+    SkMD5::Digest digest;
+    md5(bm, &digest);
 
     bm.eraseColor(SK_ColorYELLOW);
 
     result =
         codec->getPixels(info, bm.getPixels(), bm.rowBytes(), NULL, NULL, NULL);
 
     REPORTER_ASSERT(r, result == SkCodec::kSuccess);
     // verify that re-decoding gives the same result.
-    md5(bm, &digest2);
-    REPORTER_ASSERT(r, digest1 == digest2);
+    compare_to_good_digest(r, digest, bm);
 
-    SkScanlineDecoder* scanlineDecoder = codec->getScanlineDecoder(info);
+    SkAutoTDelete<SkScanlineDecoder> scanlineDecoder(codec->getScanlineDecoder(info));
     if (supportsScanlineDecoding) {
         bm.eraseColor(SK_ColorYELLOW);
         REPORTER_ASSERT(r, scanlineDecoder);
 
-        // Regular decodes should be disabled after creating a scanline decoder
+        // Regular decodes should not be affected by creating a scanline decoder
         result = codec->getPixels(info, bm.getPixels(), bm.rowBytes(), NULL, NULL, NULL);
-        REPORTER_ASSERT(r, SkCodec::kInvalidParameters == result);
+        REPORTER_ASSERT(r, SkCodec::kSuccess == result);
+        compare_to_good_digest(r, digest, bm);
+
+        bm.eraseColor(SK_ColorYELLOW);
+
         for (int y = 0; y < info.height(); y++) {
             result = scanlineDecoder->getScanlines(bm.getAddr(0, y), 1, 0);
             REPORTER_ASSERT(r, result == SkCodec::kSuccess);
         }
         // verify that scanline decoding gives the same result.
-        SkMD5::Digest digest3;
-        md5(bm, &digest3);
-        REPORTER_ASSERT(r, digest3 == digest1);
+        compare_to_good_digest(r, digest, bm);
     } else {
         REPORTER_ASSERT(r, !scanlineDecoder);
     }
 }
 
 DEF_TEST(Codec, r) {
     // WBMP
     check(r, "mandrill.wbmp", SkISize::Make(512, 512), false);
 
     // WEBP
@@ skipping 124 matching lines @@
     test_empty(r, "empty_images/zero-embedded.ico");
     test_empty(r, "empty_images/zero-width.bmp");
     test_empty(r, "empty_images/zero-height.bmp");
     test_empty(r, "empty_images/zero-width.jpg");
     test_empty(r, "empty_images/zero-height.jpg");
     test_empty(r, "empty_images/zero-width.png");
     test_empty(r, "empty_images/zero-height.png");
     test_empty(r, "empty_images/zero-width.wbmp");
     test_empty(r, "empty_images/zero-height.wbmp");
 }