1 // Copyright 2017 The Abseil Authors.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // https://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14 //
15 // Output extension hooks for the Format library.
16 // `internal::InvokeFlush` calls the appropriate flush function for the
17 // specified output argument.
18 // `BufferRawSink` is a simple output sink for a char buffer. Used by SnprintF.
19 // `FILERawSink` is a std::FILE* based sink. Used by PrintF and FprintF.
20
21 #ifndef ABSL_STRINGS_INTERNAL_STR_FORMAT_OUTPUT_H_
22 #define ABSL_STRINGS_INTERNAL_STR_FORMAT_OUTPUT_H_
23
24 #include <cstdio>
25 #include <ios>
26 #include <ostream>
27 #include <string>
28
29 #include "absl/base/port.h"
30 #include "absl/strings/string_view.h"
31
32 namespace absl {
33 ABSL_NAMESPACE_BEGIN
34 namespace str_format_internal {
35
36 // RawSink implementation that writes into a char* buffer.
37 // It will not overflow the buffer, but will keep the total count of chars
38 // that would have been written.
39 class BufferRawSink {
40 public:
BufferRawSink(char * buffer,size_t size)41 BufferRawSink(char* buffer, size_t size) : buffer_(buffer), size_(size) {}
42
total_written()43 size_t total_written() const { return total_written_; }
44 void Write(string_view v);
45
46 private:
47 char* buffer_;
48 size_t size_;
49 size_t total_written_ = 0;
50 };
51
52 // RawSink implementation that writes into a FILE*.
53 // It keeps track of the total number of bytes written and any error encountered
54 // during the writes.
55 class FILERawSink {
56 public:
FILERawSink(std::FILE * output)57 explicit FILERawSink(std::FILE* output) : output_(output) {}
58
59 void Write(string_view v);
60
count()61 size_t count() const { return count_; }
error()62 int error() const { return error_; }
63
64 private:
65 std::FILE* output_;
66 int error_ = 0;
67 size_t count_ = 0;
68 };
69
70 // Provide RawSink integration with common types from the STL.
AbslFormatFlush(std::string * out,string_view s)71 inline void AbslFormatFlush(std::string* out, string_view s) {
72 out->append(s.data(), s.size());
73 }
AbslFormatFlush(std::ostream * out,string_view s)74 inline void AbslFormatFlush(std::ostream* out, string_view s) {
75 out->write(s.data(), static_cast<std::streamsize>(s.size()));
76 }
77
AbslFormatFlush(FILERawSink * sink,string_view v)78 inline void AbslFormatFlush(FILERawSink* sink, string_view v) {
79 sink->Write(v);
80 }
81
AbslFormatFlush(BufferRawSink * sink,string_view v)82 inline void AbslFormatFlush(BufferRawSink* sink, string_view v) {
83 sink->Write(v);
84 }
85
86 // This is a SFINAE to get a better compiler error message when the type
87 // is not supported.
88 template <typename T>
89 auto InvokeFlush(T* out, string_view s) -> decltype(AbslFormatFlush(out, s)) {
90 AbslFormatFlush(out, s);
91 }
92
93 } // namespace str_format_internal
94 ABSL_NAMESPACE_END
95 } // namespace absl
96
97 #endif // ABSL_STRINGS_INTERNAL_STR_FORMAT_OUTPUT_H_
98