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_ISTREAMWRAPPER_H_
16 #define RAPIDJSON_ISTREAMWRAPPER_H_
17 
18 #include "stream.h"
19 #include <iosfwd>
20 
21 #ifdef __clang__
22 RAPIDJSON_DIAG_PUSH
RAPIDJSON_DIAG_OFF(padded)23 RAPIDJSON_DIAG_OFF(padded)
24 #endif
25 
26 #ifdef _MSC_VER
27 RAPIDJSON_DIAG_PUSH
28 RAPIDJSON_DIAG_OFF(4351) // new behavior: elements of array 'array' will be default initialized
29 #endif
30 
31 RAPIDJSON_NAMESPACE_BEGIN
32 
33 //! Wrapper of \c std::basic_istream into RapidJSON's Stream concept.
34 /*!
35     The classes can be wrapped including but not limited to:
36 
37     - \c std::istringstream
38     - \c std::stringstream
39     - \c std::wistringstream
40     - \c std::wstringstream
41     - \c std::ifstream
42     - \c std::fstream
43     - \c std::wifstream
44     - \c std::wfstream
45 
46     \tparam StreamType Class derived from \c std::basic_istream.
47 */
48 
49 template <typename StreamType>
50 class BasicIStreamWrapper {
51 public:
52     typedef typename StreamType::char_type Ch;
53     BasicIStreamWrapper(StreamType& stream) : stream_(stream), count_(), peekBuffer_() {}
54 
55     Ch Peek() const {
56         typename StreamType::int_type c = stream_.peek();
57         return RAPIDJSON_LIKELY(c != StreamType::traits_type::eof()) ? static_cast<Ch>(c) : '\0';
58     }
59 
60     Ch Take() {
61         typename StreamType::int_type c = stream_.get();
62         if (RAPIDJSON_LIKELY(c != StreamType::traits_type::eof())) {
63             count_++;
64             return static_cast<Ch>(c);
65         }
66         else
67             return '\0';
68     }
69 
70     // tellg() may return -1 when failed. So we count by ourself.
71     size_t Tell() const { return count_; }
72 
73     Ch* PutBegin() { RAPIDJSON_ASSERT(false); return 0; }
74     void Put(Ch) { RAPIDJSON_ASSERT(false); }
75     void Flush() { RAPIDJSON_ASSERT(false); }
76     size_t PutEnd(Ch*) { RAPIDJSON_ASSERT(false); return 0; }
77 
78     // For encoding detection only.
79     const Ch* Peek4() const {
80         RAPIDJSON_ASSERT(sizeof(Ch) == 1); // Only usable for byte stream.
81         int i;
82         bool hasError = false;
83         for (i = 0; i < 4; ++i) {
84             typename StreamType::int_type c = stream_.get();
85             if (c == StreamType::traits_type::eof()) {
86                 hasError = true;
87                 stream_.clear();
88                 break;
89             }
90             peekBuffer_[i] = static_cast<Ch>(c);
91         }
92         for (--i; i >= 0; --i)
93             stream_.putback(peekBuffer_[i]);
94         return !hasError ? peekBuffer_ : 0;
95     }
96 
97 private:
98     BasicIStreamWrapper(const BasicIStreamWrapper&);
99     BasicIStreamWrapper& operator=(const BasicIStreamWrapper&);
100 
101     StreamType& stream_;
102     size_t count_;  //!< Number of characters read. Note:
103     mutable Ch peekBuffer_[4];
104 };
105 
106 typedef BasicIStreamWrapper<std::istream> IStreamWrapper;
107 typedef BasicIStreamWrapper<std::wistream> WIStreamWrapper;
108 
109 #if defined(__clang__) || defined(_MSC_VER)
110 RAPIDJSON_DIAG_POP
111 #endif
112 
113 RAPIDJSON_NAMESPACE_END
114 
115 #endif // RAPIDJSON_ISTREAMWRAPPER_H_
116