filewritestream.h #1

// Tencent is pleased to support the open source community by making RapidJSON available.
// 
// Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved.
//
// Licensed under the MIT License (the "License"); you may not use this file except
// in compliance with the License. You may obtain a copy of the License at
//
// http://opensource.org/licenses/MIT
//
// Unless required by applicable law or agreed to in writing, software distributed 
// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR 
// CONDITIONS OF ANY KIND, either express or implied. See the License for the 
// specific language governing permissions and limitations under the License.

#ifndef RAPIDJSON_FILEWRITESTREAM_H_
#define RAPIDJSON_FILEWRITESTREAM_H_

#include "rapidjson.h"
#include <cstdio>

RAPIDJSON_NAMESPACE_BEGIN

//! Wrapper of C file stream for input using fread().
/*!
    \note implements Stream concept
*/
class FileWriteStream {
public:
    typedef char Ch;    //!< Character type. Only support char.

    FileWriteStream(std::FILE* fp, char* buffer, size_t bufferSize) : fp_(fp), buffer_(buffer), bufferEnd_(buffer + bufferSize), current_(buffer_) { 
        RAPIDJSON_ASSERT(fp_ != 0);
    }

    void Put(char c) { 
        if (current_ >= bufferEnd_)
            Flush();

        *current_++ = c;
    }

    void PutN(char c, size_t n) {
        size_t avail = static_cast<size_t>(bufferEnd_ - current_);
        while (n > avail) {
            std::memset(current_, c, avail);
            current_ += avail;
            Flush();
            n -= avail;
            avail = static_cast<size_t>(bufferEnd_ - current_);
        }

        if (n > 0) {
            std::memset(current_, c, n);
            current_ += n;
        }
    }

    void Flush() {
        if (current_ != buffer_) {
            fwrite(buffer_, 1, static_cast<size_t>(current_ - buffer_), fp_);
            current_ = buffer_;
        }
    }

    // Not implemented
    char Peek() const { RAPIDJSON_ASSERT(false); return 0; }
    char Take() { RAPIDJSON_ASSERT(false); return 0; }
    size_t Tell() const { RAPIDJSON_ASSERT(false); return 0; }
    char* PutBegin() { RAPIDJSON_ASSERT(false); return 0; }
    size_t PutEnd(char*) { RAPIDJSON_ASSERT(false); return 0; }

private:
    // Prohibit copy constructor & assignment operator.
    FileWriteStream(const FileWriteStream&);
    FileWriteStream& operator=(const FileWriteStream&);

    std::FILE* fp_;
    char *buffer_;
    char *bufferEnd_;
    char *current_;
};

//! Implement specialized version of PutN() with memset() for better performance.
template<>
inline void PutN(FileWriteStream& stream, char c, size_t n) {
    stream.PutN(c, n);
}

RAPIDJSON_NAMESPACE_END

#endif // RAPIDJSON_FILESTREAM_H_