filewritestream.h

Public Functions

void

PutN(FileWriteStream & stream, char c, size_t n)

Public Functions

PutN(FileWriteStream & stream, char c, size_t n)

Implement specialized version of PutN() with memset() for better performance.

  1
  2// Tencent is pleased to support the open source community by making RapidJSON available.
  3// 
  4// Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved.
  5//
  6// Licensed under the MIT License (the "License"); you may not use this file except
  7// in compliance with the License. You may obtain a copy of the License at
  8//
  9// http://opensource.org/licenses/MIT
 10//
 11// Unless required by applicable law or agreed to in writing, software distributed 
 12// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR 
 13// CONDITIONS OF ANY KIND, either express or implied. See the License for the 
 14// specific language governing permissions and limitations under the License.
 15
 16#ifndef RAPIDJSON_FILEWRITESTREAM_H_
 17#define RAPIDJSON_FILEWRITESTREAM_H_
 18
 19#include "stream.h"
 20#include <cstdio>
 21
 22#ifdef __clang__
 23RAPIDJSON_DIAG_PUSH
 24RAPIDJSON_DIAG_OFF(unreachable-code)
 25#endif
 26
 27RAPIDJSON_NAMESPACE_BEGIN
 28
 29//! Wrapper of C file stream for output using fwrite().
 30/*!
 31    \note implements Stream concept
 32*/
 33class FileWriteStream {
 34public:
 35    typedef char Ch;    //!< Character type. Only support char.
 36
 37    FileWriteStream(std::FILE* fp, char* buffer, size_t bufferSize) : fp_(fp), buffer_(buffer), bufferEnd_(buffer + bufferSize), current_(buffer_) { 
 38        RAPIDJSON_ASSERT(fp_ != 0);
 39    }
 40
 41    void Put(char c) { 
 42        if (current_ >= bufferEnd_)
 43            Flush();
 44
 45        *current_++ = c;
 46    }
 47
 48    void PutN(char c, size_t n) {
 49        size_t avail = static_cast<size_t>(bufferEnd_ - current_);
 50        while (n > avail) {
 51            std::memset(current_, c, avail);
 52            current_ += avail;
 53            Flush();
 54            n -= avail;
 55            avail = static_cast<size_t>(bufferEnd_ - current_);
 56        }
 57
 58        if (n > 0) {
 59            std::memset(current_, c, n);
 60            current_ += n;
 61        }
 62    }
 63
 64    void Flush() {
 65        if (current_ != buffer_) {
 66            size_t result = std::fwrite(buffer_, 1, static_cast<size_t>(current_ - buffer_), fp_);
 67            if (result < static_cast<size_t>(current_ - buffer_)) {
 68                // failure deliberately ignored at this time
 69                // added to avoid warn_unused_result build errors
 70            }
 71            current_ = buffer_;
 72        }
 73    }
 74
 75    // Not implemented
 76    char Peek() const { RAPIDJSON_ASSERT(false); return 0; }
 77    char Take() { RAPIDJSON_ASSERT(false); return 0; }
 78    size_t Tell() const { RAPIDJSON_ASSERT(false); return 0; }
 79    char* PutBegin() { RAPIDJSON_ASSERT(false); return 0; }
 80    size_t PutEnd(char*) { RAPIDJSON_ASSERT(false); return 0; }
 81
 82private:
 83    // Prohibit copy constructor & assignment operator.
 84    FileWriteStream(const FileWriteStream&);
 85    FileWriteStream& operator=(const FileWriteStream&);
 86
 87    std::FILE* fp_;
 88    char *buffer_;
 89    char *bufferEnd_;
 90    char *current_;
 91};
 92
 93//! Implement specialized version of PutN() with memset() for better performance.
 94template<>
 95inline void PutN(FileWriteStream& stream, char c, size_t n) {
 96    stream.PutN(c, n);
 97}
 98
 99RAPIDJSON_NAMESPACE_END
100
101#ifdef __clang__
102RAPIDJSON_DIAG_POP
103#endif
104
105#endif // RAPIDJSON_FILESTREAM_H_
106