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      1 // Tencent is pleased to support the open source community by making RapidJSON available.
      2 //
      3 // Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved.
      4 //
      5 // Licensed under the MIT License (the "License"); you may not use this file except
      6 // in compliance with the License. You may obtain a copy of the License at
      7 //
      8 // http://opensource.org/licenses/MIT
      9 //
     10 // Unless required by applicable law or agreed to in writing, software distributed
     11 // under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
     12 // CONDITIONS OF ANY KIND, either express or implied. See the License for the
     13 // specific language governing permissions and limitations under the License.
     14 
     15 #ifndef RAPIDJSON_FILEREADSTREAM_H_
     16 #define RAPIDJSON_FILEREADSTREAM_H_
     17 
     18 #include "rapidjson.h"
     19 #include <cstdio>
     20 
     21 RAPIDJSON_NAMESPACE_BEGIN
     22 
     23 //! File byte stream for input using fread().
     24 /*!
     25     \note implements Stream concept
     26 */
     27 class FileReadStream {
     28 public:
     29     typedef char Ch;    //!< Character type (byte).
     30 
     31     //! Constructor.
     32     /*!
     33         \param fp File pointer opened for read.
     34         \param buffer user-supplied buffer.
     35         \param bufferSize size of buffer in bytes. Must >=4 bytes.
     36     */
     37     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) {
     38         RAPIDJSON_ASSERT(fp_ != 0);
     39         RAPIDJSON_ASSERT(bufferSize >= 4);
     40         Read();
     41     }
     42 
     43     Ch Peek() const { return *current_; }
     44     Ch Take() { Ch c = *current_; Read(); return c; }
     45     size_t Tell() const { return count_ + static_cast<size_t>(current_ - buffer_); }
     46 
     47     // Not implemented
     48     void Put(Ch) { RAPIDJSON_ASSERT(false); }
     49     void Flush() { RAPIDJSON_ASSERT(false); }
     50     Ch* PutBegin() { RAPIDJSON_ASSERT(false); return 0; }
     51     size_t PutEnd(Ch*) { RAPIDJSON_ASSERT(false); return 0; }
     52 
     53     // For encoding detection only.
     54     const Ch* Peek4() const {
     55         return (current_ + 4 <= bufferLast_) ? current_ : 0;
     56     }
     57 
     58 private:
     59     void Read() {
     60         if (current_ < bufferLast_)
     61             ++current_;
     62         else if (!eof_) {
     63             count_ += readCount_;
     64             readCount_ = fread(buffer_, 1, bufferSize_, fp_);
     65             bufferLast_ = buffer_ + readCount_ - 1;
     66             current_ = buffer_;
     67 
     68             if (readCount_ < bufferSize_) {
     69                 buffer_[readCount_] = '\0';
     70                 ++bufferLast_;
     71                 eof_ = true;
     72             }
     73         }
     74     }
     75 
     76     std::FILE* fp_;
     77     Ch *buffer_;
     78     size_t bufferSize_;
     79     Ch *bufferLast_;
     80     Ch *current_;
     81     size_t readCount_;
     82     size_t count_;  //!< Number of characters read
     83     bool eof_;
     84 };
     85 
     86 RAPIDJSON_NAMESPACE_END
     87 
     88 #endif // RAPIDJSON_FILESTREAM_H_
     89