SkBlockMemoryStream implements peek()

src/core/SkStream.cpp

Index: src/core/SkStream.cpp
diff --git a/src/core/SkStream.cpp b/src/core/SkStream.cpp
index ad67a0ba7db43759c8c6f9e03ff2f25bc0ac43ca..4870448e79b58f7a7ab3e03168686276cad4f048 100644
--- a/src/core/SkStream.cpp
+++ b/src/core/SkStream.cpp
@@ -724,6 +724,29 @@ public:
         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;