1/*
2 * Copyright 2015 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#ifndef SkRWBuffer_DEFINED
9#define SkRWBuffer_DEFINED
10
11#include "SkRefCnt.h"
12
13struct SkBufferBlock;
14struct SkBufferHead;
15class SkRWBuffer;
16class SkStreamAsset;
17
18/**
19 *  Contains a read-only, thread-sharable block of memory. To access the memory, the caller must
20 *  instantiate a local iterator, as the memory is stored in 1 or more contiguous blocks.
21 */
22class SkROBuffer : public SkRefCnt {
23public:
24    /**
25     *  Return the logical length of the data owned/shared by this buffer. It may be stored in
26     *  multiple contiguous blocks, accessible via the iterator.
27     */
28    size_t size() const { return fUsed; }
29
30    class Iter {
31    public:
32        Iter(const SkROBuffer*);
33
34        void reset(const SkROBuffer*);
35
36        /**
37         *  Return the current continuous block of memory, or NULL if the iterator is exhausted
38         */
39        const void* data() const;
40
41        /**
42         *  Returns the number of bytes in the current continguous block of memory, or 0 if the
43         *  iterator is exhausted.
44         */
45        size_t size() const;
46
47        /**
48         *  Advance to the next contiguous block of memory, returning true if there is another
49         *  block, or false if the iterator is exhausted.
50         */
51        bool next();
52
53    private:
54        const SkBufferBlock* fBlock;
55        size_t               fRemaining;
56    };
57
58private:
59    SkROBuffer(const SkBufferHead* head, size_t used);
60    virtual ~SkROBuffer();
61
62    const SkBufferHead* fHead;
63    const size_t        fUsed;
64
65    friend class SkRWBuffer;
66};
67
68/**
69 *  Accumulates bytes of memory that are "appended" to it, growing internal storage as needed.
70 *  The growth is done such that at any time, a RBuffer or StreamAsset can be snapped off, which
71 *  can see the previously stored bytes, but which will be unaware of any future writes.
72 */
73class SkRWBuffer {
74public:
75    SkRWBuffer(size_t initialCapacity = 0);
76    ~SkRWBuffer();
77
78    size_t size() const { return fTotalUsed; }
79    void append(const void* buffer, size_t length);
80    void* append(size_t length);
81
82    SkROBuffer* newRBufferSnapshot() const;
83    SkStreamAsset* newStreamSnapshot() const;
84
85#ifdef SK_DEBUG
86    void validate() const;
87#else
88    void validate() const {}
89#endif
90
91private:
92    SkBufferHead*   fHead;
93    SkBufferBlock*  fTail;
94    size_t          fTotalUsed;
95};
96
97#endif
98