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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
22RAPIDJSON_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
177RAPIDJSON_NAMESPACE_END
178
179#endif // RAPIDJSON_STREAM_H_
Encoding
Concept for encoding of Unicode characters.
Stream
Concept for reading and writing characters.
RAPIDJSON_ASSERT
#define RAPIDJSON_ASSERT(x)
Assertion.
Definition rapidjson.h:402
rapidjson::PutUnsafe
void PutUnsafe(Stream &stream, typename Stream::Ch c)
Write character to a stream, presuming buffer is reserved.
Definition stream.h:91
rapidjson::PutN
void PutN(FileWriteStream &stream, char c, size_t n)
Implement specialized version of PutN() with memset() for better performance.
Definition filewritestream.h:94
rapidjson::PutReserve
void PutReserve(Stream &stream, size_t count)
Reserve n characters for writing to a stream.
Definition stream.h:84
rapidjson.h
common definitions and configuration
rapidjson::GenericInsituStringStream
A read-write string stream.
Definition stream.h:144
rapidjson::GenericStringStream
Read-only string stream.
Definition stream.h:110
rapidjson::GenericStringStream::head_
const Ch * head_
Original head of the string.
Definition stream.h:125
rapidjson::GenericStringStream::src_
const Ch * src_
Current read position.
Definition stream.h:124
rapidjson::StreamTraits
Provides additional information for stream.
Definition stream.h:73