SkBlockMemoryStream implements peek()

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 706 matching lines @@
             fCurrentOffset = 0;
         }
         SkASSERT(false);
         return 0;
     }
 
     bool isAtEnd() const override {
         return fOffset == fSize;
     }
 
+    bool peek(void* buff, size_t size) const override {
+        if (fOffset + size > fSize) {
+            return false;
+        }
+        if (!buff) {

[scroggo, 2015/05/20 15:43:35]

In other implementations, we SkASSERT(buff). They should all behave the same
(the documentation also states that buff must not be null). I don't understand
why the caller would want to get a return value of true if they passed a null
buffer (it seems like they made a mistake if they passed null).

[hal.canary, 2015/05/21 13:28:02]

Done.

+            return true;
+        }
+        char* buffer = static_cast<char*>(buff);
+        SkDynamicMemoryWStream::Block const * current = fCurrent;
+        size_t currentOffset = fCurrentOffset;
+        while (size) {
+            SkASSERT(current);
+            size_t bytesFromCurrent =
+                SkTMin(current->written() - currentOffset, size);
+            memcpy(buffer, current->start() + currentOffset, bytesFromCurrent);
+            size -= bytesFromCurrent;
+            buffer += bytesFromCurrent;
+            current = current->fNext;
+            currentOffset = 0;
+        }
+        return true;
+    }
+
     bool rewind() override {
         fCurrent = fBlockMemory->fHead;
         fOffset = 0;
         fCurrentOffset = 0;
         return true;
     }
 
     SkBlockMemoryStream* duplicate() const override {
         return SkNEW_ARGS(SkBlockMemoryStream, (fBlockMemory.get(), fSize));
     }
@@ skipping 185 matching lines @@
     SkDynamicMemoryWStream tempStream;
     const size_t bufferSize = 4096;
     char buffer[bufferSize];
     do {
         size_t bytesRead = stream->read(buffer, bufferSize);
         tempStream.write(buffer, bytesRead);
     } while (!stream->isAtEnd());
     return tempStream.detachAsStream();  // returns a SkBlockMemoryStream,
                                          // cheaper than copying to SkData
 }