ceph/src/rapidjson/include/rapidjson/stream.h

   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 #include "rapidjson.h"
  16
  17 #ifndef RAPIDJSON_STREAM_H_
  18 #define RAPIDJSON_STREAM_H_
  19
  20 #include "encodings.h"
  21
  22 RAPIDJSON_NAMESPACE_BEGIN
  23
  24 ///////////////////////////////////////////////////////////////////////////////
  25 //  Stream
  26
  27 /*! \class rapidjson::Stream
  28     \brief Concept for reading and writing characters.
  29
  30     For read-only stream, no need to implement PutBegin(), Put(), Flush() and PutEnd().
  31
  32     For write-only stream, only need to implement Put() and Flush().
  33
  34 \code
  35 concept Stream {
  36     typename Ch;    //!< Character type of the stream.
  37
  38     //! Read the current character from stream without moving the read cursor.
  39     Ch Peek() const;
  40
  41     //! Read the current character from stream and moving the read cursor to next character.
  42     Ch Take();
  43
  44     //! Get the current read cursor.
  45     //! \return Number of characters read from start.
  46     size_t Tell();
  47
  48     //! Begin writing operation at the current read pointer.
  49     //! \return The begin writer pointer.
  50     Ch* PutBegin();
  51
  52     //! Write a character.
  53     void Put(Ch c);
  54
  55     //! Flush the buffer.
  56     void Flush();
  57
  58     //! End the writing operation.
  59     //! \param begin The begin write pointer returned by PutBegin().
  60     //! \return Number of characters written.
  61     size_t PutEnd(Ch* begin);
  62 }
  63 \endcode
  64 */
  65
  66 //! Provides additional information for stream.
  67 /*!
  68     By using traits pattern, this type provides a default configuration for stream.
  69     For custom stream, this type can be specialized for other configuration.
  70     See TEST(Reader, CustomStringStream) in readertest.cpp for example.
  71 */
  72 template<typename Stream>
  73 struct StreamTraits {
  74     //! Whether to make local copy of stream for optimization during parsing.
  75     /*!
  76         By default, for safety, streams do not use local copy optimization.
  77         Stream that can be copied fast should specialize this, like StreamTraits<StringStream>.
  78     */
  79     enum { copyOptimization = 0 };
  80 };
  81
  82 //! Reserve n characters for writing to a stream.
  83 template<typename Stream>
  84 inline void PutReserve(Stream& stream, size_t count) {
  85     (void)stream;
  86     (void)count;
  87 }
  88
  89 //! Write character to a stream, presuming buffer is reserved.
  90 template<typename Stream>
  91 inline void PutUnsafe(Stream& stream, typename Stream::Ch c) {
  92     stream.Put(c);
  93 }
  94
  95 //! Put N copies of a character to a stream.
  96 template<typename Stream, typename Ch>
  97 inline void PutN(Stream& stream, Ch c, size_t n) {
  98     PutReserve(stream, n);
  99     for (size_t i = 0; i < n; i++)
 100         PutUnsafe(stream, c);
 101 }
 102
 103 ///////////////////////////////////////////////////////////////////////////////
 104 // StringStream
 105
 106 //! Read-only string stream.
 107 /*! \note implements Stream concept
 108 */
 109 template <typename Encoding>
 110 struct GenericStringStream {
 111     typedef typename Encoding::Ch Ch;
 112
 113     GenericStringStream(const Ch *src) : src_(src), head_(src) {}
 114
 115     Ch Peek() const { return *src_; }
 116     Ch Take() { return *src_++; }
 117     size_t Tell() const { return static_cast<size_t>(src_ - head_); }
 118
 119     Ch* PutBegin() { RAPIDJSON_ASSERT(false); return 0; }
 120     void Put(Ch) { RAPIDJSON_ASSERT(false); }
 121     void Flush() { RAPIDJSON_ASSERT(false); }
 122     size_t PutEnd(Ch*) { RAPIDJSON_ASSERT(false); return 0; }
 123
 124     const Ch* src_;     //!< Current read position.
 125     const Ch* head_;    //!< Original head of the string.
 126 };
 127
 128 template <typename Encoding>
 129 struct StreamTraits<GenericStringStream<Encoding> > {
 130     enum { copyOptimization = 1 };
 131 };
 132
 133 //! String stream with UTF8 encoding.
 134 typedef GenericStringStream<UTF8<> > StringStream;
 135
 136 ///////////////////////////////////////////////////////////////////////////////
 137 // InsituStringStream
 138
 139 //! A read-write string stream.
 140 /*! This string stream is particularly designed for in-situ parsing.
 141     \note implements Stream concept
 142 */
 143 template <typename Encoding>
 144 struct GenericInsituStringStream {
 145     typedef typename Encoding::Ch Ch;
 146
 147     GenericInsituStringStream(Ch *src) : src_(src), dst_(0), head_(src) {}
 148
 149     // Read
 150     Ch Peek() { return *src_; }
 151     Ch Take() { return *src_++; }
 152     size_t Tell() { return static_cast<size_t>(src_ - head_); }
 153
 154     // Write
 155     void Put(Ch c) { RAPIDJSON_ASSERT(dst_ != 0); *dst_++ = c; }
 156
 157     Ch* PutBegin() { return dst_ = src_; }
 158     size_t PutEnd(Ch* begin) { return static_cast<size_t>(dst_ - begin); }
 159     void Flush() {}
 160
 161     Ch* Push(size_t count) { Ch* begin = dst_; dst_ += count; return begin; }
 162     void Pop(size_t count) { dst_ -= count; }
 163
 164     Ch* src_;
 165     Ch* dst_;
 166     Ch* head_;
 167 };
 168
 169 template <typename Encoding>
 170 struct StreamTraits<GenericInsituStringStream<Encoding> > {
 171     enum { copyOptimization = 1 };
 172 };
 173
 174 //! Insitu string stream with UTF8 encoding.
 175 typedef GenericInsituStringStream<UTF8<> > InsituStringStream;
 176
 177 RAPIDJSON_NAMESPACE_END
 178
 179 #endif // RAPIDJSON_STREAM_H_