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1 /*
2  * Copyright (C) 2013 Google Inc. All rights reserved.
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions are
6  * met:
7  *
8  *     * Redistributions of source code must retain the above copyright
9  * notice, this list of conditions and the following disclaimer.
10  *     * Redistributions in binary form must reproduce the above
11  * copyright notice, this list of conditions and the following disclaimer
12  * in the documentation and/or other materials provided with the
13  * distribution.
14  *     * Neither the name of Google Inc. nor the names of its
15  * contributors may be used to endorse or promote products derived from
16  * this software without specific prior written permission.
17  *
18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29  */
30 
31 #ifndef ArrayBufferBuilder_h
32 #define ArrayBufferBuilder_h
33 
34 #include "wtf/ArrayBuffer.h"
35 #include "wtf/Noncopyable.h"
36 #include "wtf/RefPtr.h"
37 #include "wtf/text/WTFString.h"
38 
39 namespace WTF {
40 
41 // A utility class to build an ArrayBuffer instance. Validity must be checked
42 // by isValid() before using an instance.
43 class WTF_EXPORT ArrayBufferBuilder {
44     // Disallow copying since it's expensive and we don't want code to do it by
45     // accident.
46     WTF_MAKE_NONCOPYABLE(ArrayBufferBuilder);
47 
48 public:
49     // Creates an ArrayBufferBuilder using the default capacity.
50     ArrayBufferBuilder();
51 
ArrayBufferBuilder(unsigned capacity)52     ArrayBufferBuilder(unsigned capacity)
53         : m_bytesUsed(0)
54         , m_variableCapacity(true)
55     {
56         m_buffer = ArrayBuffer::create(capacity, 1);
57     }
58 
isValid()59     bool isValid() const
60     {
61         return m_buffer;
62     }
63 
64     // Appending empty data is not allowed.
65     unsigned append(const char* data, unsigned length);
66 
67     // Returns the accumulated data as an ArrayBuffer instance. If needed,
68     // creates a new ArrayBuffer instance and copies contents from the internal
69     // buffer to it. Otherwise, returns a PassRefPtr pointing to the internal
70     // buffer.
71     PassRefPtr<ArrayBuffer> toArrayBuffer();
72 
73     // Converts the accumulated data into a String using the default encoding.
74     String toString();
75 
76     // Number of bytes currently accumulated.
byteLength()77     unsigned byteLength() const
78     {
79         return m_bytesUsed;
80     }
81 
82     // Number of bytes allocated.
capacity()83     unsigned capacity() const
84     {
85         return m_buffer->byteLength();
86     }
87 
88     void shrinkToFit();
89 
data()90     const void* data() const
91     {
92         return m_buffer->data();
93     }
94 
95     // If set to false, the capacity won't be expanded and when appended data
96     // overflows, the overflowed part will be dropped.
setVariableCapacity(bool value)97     void setVariableCapacity(bool value)
98     {
99         m_variableCapacity = value;
100     }
101 
102 private:
103     // Expands the size of m_buffer to size + m_bytesUsed bytes. Returns true
104     // iff successful. If reallocation is needed, copies only data in
105     // [0, m_bytesUsed) range.
106     bool expandCapacity(unsigned size);
107 
108     unsigned m_bytesUsed;
109     bool m_variableCapacity;
110     RefPtr<ArrayBuffer> m_buffer;
111 };
112 
113 } // namespace WTF
114 
115 using WTF::ArrayBufferBuilder;
116 
117 #endif // ArrayBufferBuilder_h
118