Prototype of RAW decoding in Skia.

src/core/SkStream.cpp

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkStream.h"
@@ skipping 870 matching lines @@
     if (stream->hasLength()) {
         const size_t length = stream->getLength();
         void* dst = storage->reset(length);
         if (stream->read(dst, length) != length) {
             return 0;
         }
         return length;
     }
 
     SkDynamicMemoryWStream tempStream;
-    // Arbitrary buffer size.
-#if defined(GOOGLE3)
-    // Stack frame size is limited in GOOGLE3.
-    const size_t bufferSize = 8 * 1024; // 8KB
-#else
-    const size_t bufferSize = 256 * 1024; // 256KB
-#endif
-    char buffer[bufferSize];
-    SkDEBUGCODE(size_t debugLength = 0;)
-    do {
-        size_t bytesRead = stream->read(buffer, bufferSize);
-        tempStream.write(buffer, bytesRead);
-        SkDEBUGCODE(debugLength += bytesRead);
-        SkASSERT(tempStream.bytesWritten() == debugLength);
-    } while (!stream->isAtEnd());
+    if (!SkStreamCopy(&tempStream, stream)) {
+        return 0;
+    }
     const size_t length = tempStream.bytesWritten();
     void* dst = storage->reset(length);
     tempStream.copyTo(dst);
     return length;
 }
 
 // Declared in SkStreamPriv.h:
 SkData* SkCopyStreamToData(SkStream* stream) {
     SkASSERT(stream != nullptr);
 
@@ skipping 53 matching lines @@
     while (true) {
         count = input->read(scratch, sizeof(scratch));
         if (0 == count) {
             return true;
         }
         if (!out->write(scratch, count)) {
             return false;
         }
     }
 }
+
+// TODO: optimize for the special case when the input is SkMemoryStream.

[scroggo, 2016/01/08 19:11:49]

The optimization is actually elsewhere - you shouldn't need to call SkStreamCopy
if it's a memory stream (you should be able to just grab its SkData directly).

[yujieqin, 2016/01/11 14:03:08]

Not sure what you mean here, I moved the TODO into the SkRawCodec.cpp where this
function is called. I think we can still keep it as TODO, right?

+bool SkStreamCopy(SkDynamicMemoryWStream* out, SkStream* input) {
+    // Arbitrary buffer size.
+#if defined(GOOGLE3)
+    // Stack frame size is limited in GOOGLE3.
+    const size_t bufferSize = 8 * 1024; // 8KB
+#else
+    const size_t bufferSize = 256 * 1024; // 256KB
+#endif
+    char buffer[bufferSize];
+    SkDEBUGCODE(size_t debugLength = 0;)
+    do {
+        size_t bytesRead = input->read(buffer, bufferSize);
+        if (!out->write(buffer, bytesRead)) {
+            return false;
+        }
+        SkDEBUGCODE(debugLength += bytesRead);
+        SkASSERT(out->bytesWritten() == debugLength);
+    } while (!input->isAtEnd());
+    return true;
+}