Move SkRWBuffer.h to include/ and add SK_API

src/core/SkRWBuffer.h

-/*
- * Copyright 2015 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#ifndef SkRWBuffer_DEFINED
-#define SkRWBuffer_DEFINED
-
-#include "SkRefCnt.h"
-
-struct SkBufferBlock;
-struct SkBufferHead;
-class SkRWBuffer;
-class SkStreamAsset;
-
-/**
- *  Contains a read-only, thread-sharable block of memory. To access the memory, the caller must
- *  instantiate a local iterator, as the memory is stored in 1 or more contiguous blocks.
- */
-class SkROBuffer : public SkRefCnt {
-public:
-    /**
-     *  Return the logical length of the data owned/shared by this buffer. It may be stored in
-     *  multiple contiguous blocks, accessible via the iterator.
-     */
-    size_t size() const { return fUsed; }
-    
-    class Iter {
-    public:
-        Iter(const SkROBuffer*);
-
-        void reset(const SkROBuffer*);
-
-        /**
-         *  Return the current continuous block of memory, or nullptr if the iterator is exhausted
-         */
-        const void* data() const;
-
-        /**
-         *  Returns the number of bytes in the current continguous block of memory, or 0 if the
-         *  iterator is exhausted.
-         */
-        size_t size() const;
-
-        /**
-         *  Advance to the next contiguous block of memory, returning true if there is another
-         *  block, or false if the iterator is exhausted.
-         */
-        bool next();
-        
-    private:
-        const SkBufferBlock* fBlock;
-        size_t               fRemaining;
-    };
-
-private:
-    SkROBuffer(const SkBufferHead* head, size_t used);
-    virtual ~SkROBuffer();
-    
-    const SkBufferHead* fHead;
-    const size_t        fUsed;
-    
-    friend class SkRWBuffer;
-};
-
-/**
- *  Accumulates bytes of memory that are "appended" to it, growing internal storage as needed.
- *  The growth is done such that at any time, a RBuffer or StreamAsset can be snapped off, which
- *  can see the previously stored bytes, but which will be unaware of any future writes.
- */
-class SkRWBuffer {
-public:
-    SkRWBuffer(size_t initialCapacity = 0);
-    ~SkRWBuffer();
-    
-    size_t size() const { return fTotalUsed; }
-    void append(const void* buffer, size_t length);
-    void* append(size_t length);
-
-    SkROBuffer* newRBufferSnapshot() const;
-    SkStreamAsset* newStreamSnapshot() const;
-    
-#ifdef SK_DEBUG
-    void validate() const;
-#else
-    void validate() const {}
-#endif
-    
-private:
-    SkBufferHead*   fHead;
-    SkBufferBlock*  fTail;
-    size_t          fTotalUsed;
-};
-
-#endif