1/*
2 * Copyright 2011 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 SkData_DEFINED
9#define SkData_DEFINED
10
11#include "SkRefCnt.h"
12
13struct SkFILE;
14class SkStream;
15
16/**
17 *  SkData holds an immutable data buffer. Not only is the data immutable,
18 *  but the actual ptr that is returned (by data() or bytes()) is guaranteed
19 *  to always be the same for the life of this instance.
20 */
21class SK_API SkData : public SkRefCnt {
22public:
23    SK_DECLARE_INST_COUNT(SkData)
24
25    /**
26     *  Returns the number of bytes stored.
27     */
28    size_t size() const { return fSize; }
29
30    bool isEmpty() const { return 0 == fSize; }
31
32    /**
33     *  Returns the ptr to the data.
34     */
35    const void* data() const { return fPtr; }
36
37    /**
38     *  Like data(), returns a read-only ptr into the data, but in this case
39     *  it is cast to uint8_t*, to make it easy to add an offset to it.
40     */
41    const uint8_t* bytes() const {
42        return reinterpret_cast<const uint8_t*>(fPtr);
43    }
44
45    /**
46     *  USE WITH CAUTION.
47     *  This call will assert that the refcnt is 1, as a precaution against modifying the
48     *  contents when another client/thread has access to the data.
49     */
50    void* writable_data() {
51        if (fSize) {
52            // only assert we're unique if we're not empty
53            SkASSERT(this->unique());
54        }
55        return fPtr;
56    }
57
58    /**
59     *  Helper to copy a range of the data into a caller-provided buffer.
60     *  Returns the actual number of bytes copied, after clamping offset and
61     *  length to the size of the data. If buffer is NULL, it is ignored, and
62     *  only the computed number of bytes is returned.
63     */
64    size_t copyRange(size_t offset, size_t length, void* buffer) const;
65
66    /**
67     *  Returns true if these two objects have the same length and contents,
68     *  effectively returning 0 == memcmp(...)
69     */
70    bool equals(const SkData* other) const;
71
72    /**
73     *  Function that, if provided, will be called when the SkData goes out
74     *  of scope, allowing for custom allocation/freeing of the data.
75     */
76    typedef void (*ReleaseProc)(const void* ptr, size_t length, void* context);
77
78    /**
79     *  Create a new dataref by copying the specified data
80     */
81    static SkData* NewWithCopy(const void* data, size_t length);
82
83    /**
84     *  Create a new data with uninitialized contents. The caller should call writable_data()
85     *  to write into the buffer, but this must be done before another ref() is made.
86     */
87    static SkData* NewUninitialized(size_t length);
88
89    /**
90     *  Create a new dataref by copying the specified c-string
91     *  (a null-terminated array of bytes). The returned SkData will have size()
92     *  equal to strlen(cstr) + 1. If cstr is NULL, it will be treated the same
93     *  as "".
94     */
95    static SkData* NewWithCString(const char cstr[]);
96
97    /**
98     *  Create a new dataref, taking the data ptr as is, and using the
99     *  releaseproc to free it. The proc may be NULL.
100     */
101    static SkData* NewWithProc(const void* data, size_t length, ReleaseProc proc, void* context);
102
103    /**
104     *  Call this when the data parameter is already const and will outlive the lifetime of the
105     *  SkData. Suitable for with const globals.
106     */
107    static SkData* NewWithoutCopy(const void* data, size_t length) {
108        return NewWithProc(data, length, NULL, NULL);
109    }
110
111    /**
112     *  Create a new dataref from a pointer allocated by malloc. The Data object
113     *  takes ownership of that allocation, and will handling calling sk_free.
114     */
115    static SkData* NewFromMalloc(const void* data, size_t length);
116
117    /**
118     *  Create a new dataref the file with the specified path.
119     *  If the file cannot be opened, this returns NULL.
120     */
121    static SkData* NewFromFileName(const char path[]);
122
123    /**
124     *  Create a new dataref from a SkFILE.
125     *  This does not take ownership of the SkFILE, nor close it.
126     *  The caller is free to close the SkFILE at its convenience.
127     *  The SkFILE must be open for reading only.
128     *  Returns NULL on failure.
129     */
130    static SkData* NewFromFILE(SkFILE* f);
131
132    /**
133     *  Create a new dataref from a file descriptor.
134     *  This does not take ownership of the file descriptor, nor close it.
135     *  The caller is free to close the file descriptor at its convenience.
136     *  The file descriptor must be open for reading only.
137     *  Returns NULL on failure.
138     */
139    static SkData* NewFromFD(int fd);
140
141    /**
142     *  Attempt to read size bytes into a SkData. If the read succeeds, return the data,
143     *  else return NULL. Either way the stream's cursor may have been changed as a result
144     *  of calling read().
145     */
146    static SkData* NewFromStream(SkStream*, size_t size);
147
148    /**
149     *  Create a new dataref using a subset of the data in the specified
150     *  src dataref.
151     */
152    static SkData* NewSubset(const SkData* src, size_t offset, size_t length);
153
154    /**
155     *  Returns a new empty dataref (or a reference to a shared empty dataref).
156     *  New or shared, the caller must see that unref() is eventually called.
157     */
158    static SkData* NewEmpty();
159
160private:
161    ReleaseProc fReleaseProc;
162    void*       fReleaseProcContext;
163
164    void*       fPtr;
165    size_t      fSize;
166
167    SkData(const void* ptr, size_t size, ReleaseProc, void* context);
168    SkData(size_t size);   // inplace new/delete
169    virtual ~SkData();
170
171    virtual void internal_dispose() const SK_OVERRIDE;
172
173    // Called the first time someone calls NewEmpty to initialize the singleton.
174    static SkData* NewEmptyImpl();
175    static void DeleteEmpty(SkData*);
176
177    // shared internal factory
178    static SkData* PrivateNewWithCopy(const void* srcOrNull, size_t length);
179
180    typedef SkRefCnt INHERITED;
181};
182
183/** Typedef of SkAutoTUnref<SkData> for automatically unref-ing a SkData. */
184typedef SkAutoTUnref<SkData> SkAutoDataUnref;
185
186#endif
187