filereadstream.h Source File

filereadstream.h Source File#

Composable Kernel: filereadstream.h Source File
// 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.
//
// 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_FILEREADSTREAM_H_
#define RAPIDJSON_FILEREADSTREAM_H_
 
#include "stream.h"
#include <cstdio>
 
#ifdef __clang__
RAPIDJSON_DIAG_PUSH
RAPIDJSON_DIAG_OFF(padded)
RAPIDJSON_DIAG_OFF(unreachable - code)
RAPIDJSON_DIAG_OFF(missing - noreturn)
#endif
 
RAPIDJSON_NAMESPACE_BEGIN
class FileReadStream
{
    public:
    typedef char Ch; 
    FileReadStream(std::FILE* fp, char* buffer, size_t bufferSize)
        : fp_(fp),
          buffer_(buffer),
          bufferSize_(bufferSize),
          bufferLast_(0),
          current_(buffer_),
          readCount_(0),
          count_(0),
          eof_(false)
    {
        RAPIDJSON_ASSERT(fp_ != 0);
        RAPIDJSON_ASSERT(bufferSize >= 4);
        Read();
    }
 
    Ch Peek() const { return *current_; }
    Ch Take()
    {
        Ch c = *current_;
        Read();
        return c;
    }
    size_t Tell() const { return count_ + static_cast<size_t>(current_ - buffer_); }
 
    // Not implemented
    void Put(Ch) { RAPIDJSON_ASSERT(false); }
    void Flush() { RAPIDJSON_ASSERT(false); }
    Ch* PutBegin()
    {
        RAPIDJSON_ASSERT(false);
        return 0;
    }
    size_t PutEnd(Ch*)
    {
        RAPIDJSON_ASSERT(false);
        return 0;
    }
 
    // For encoding detection only.
    const Ch* Peek4() const { return (current_ + 4 - !eof_ <= bufferLast_) ? current_ : 0; }
 
    private:
    void Read()
    {
        if(current_ < bufferLast_)
            ++current_;
        else if(!eof_)
        {
            count_ += readCount_;
            readCount_  = std::fread(buffer_, 1, bufferSize_, fp_);
            bufferLast_ = buffer_ + readCount_ - 1;
            current_    = buffer_;
 
            if(readCount_ < bufferSize_)
            {
                buffer_[readCount_] = '\0';
                ++bufferLast_;
                eof_ = true;
            }
        }
    }
 
    std::FILE* fp_;
    Ch* buffer_;
    size_t bufferSize_;
    Ch* bufferLast_;
    Ch* current_;
    size_t readCount_;
    size_t count_; 
    bool eof_;
};
 
RAPIDJSON_NAMESPACE_END
 
#ifdef __clang__
RAPIDJSON_DIAG_POP
#endif
 
#endif // RAPIDJSON_FILESTREAM_H_