Source/wtf/ArrayBufferBuilder.h

/*
 * Copyright (C) 2013 Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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 */

#ifndef ArrayBufferBuilder_h
#define ArrayBufferBuilder_h

#include "wtf/ArrayBuffer.h"
#include "wtf/Noncopyable.h"
#include "wtf/RefPtr.h"
#include "wtf/text/WTFString.h"

namespace WTF {

// A utility class to build an ArrayBuffer instance.
class WTF_EXPORT ArrayBufferBuilder {
    // Disallow copying since it's expensive and we don't want code to do it by
    // accident.
    WTF_MAKE_NONCOPYABLE(ArrayBufferBuilder);

public:
    // Creates an ArrayBufferBuilder using the default capacity.
    ArrayBufferBuilder();

    ArrayBufferBuilder(unsigned capacity)
        : m_bytesUsed(0)
        , m_variableCapacity(true)
    {
        m_buffer = ArrayBuffer::create(capacity, 1);
    }

    unsigned append(const char* data, unsigned length);

    // Returns the accumulated data as an ArrayBuffer instance. If needed,
    // creates a new ArrayBuffer instance and copies contents from the internal
    // buffer to it. Otherwise, returns a PassRefPtr pointing to the internal
    // buffer.
    PassRefPtr<ArrayBuffer> toArrayBuffer();

    // Converts the accumulated data into a String using the default encoding.
    String toString();

    // Number of bytes currently accumulated.
    unsigned byteLength() const
    {
        return m_bytesUsed;
    }

    // Number of bytes allocated.
    unsigned capacity() const
    {
        return m_buffer->byteLength();
    }

    void shrinkToFit();

    const void* data() const
    {
        return m_buffer->data();
    }

    // If set to false, the capacity won't be expanded and when appended data
    // overflows, the overflowed part will be dropped.
    void setVariableCapacity(bool value)
    {
        m_variableCapacity = value;
    }

private:
    // Expands the size of m_buffer to size + m_bytesUsed bytes. Returns true
    // iff successful. If reallocation is needed, copies only data in
    // [0, m_bytesUsed) range.
    bool expandCapacity(unsigned size);

    unsigned m_bytesUsed;
    bool m_variableCapacity;
    RefPtr<ArrayBuffer> m_buffer;
};

} // namespace WTF

using WTF::ArrayBufferBuilder;

#endif // ArrayBufferBuilder_h