filereadstream.h

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// 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_FILEREADSTREAM_H_
#define RAPIDJSON_FILEREADSTREAM_H_

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

#if __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

#if __clang__
RAPIDJSON_DIAG_POP
#endif

#endif  // RAPIDJSON_FILESTREAM_H_