1 // Formatting library for C++ - std::ostream support
2 //
3 // Copyright (c) 2012 - present, Victor Zverovich
4 // All rights reserved.
5 //
6 // For the license information refer to format.h.
7
8 #ifndef FMT_OSTREAM_H_
9 #define FMT_OSTREAM_H_
10
11 #include <ostream>
12 #include "format.h"
13
14 FMT_BEGIN_NAMESPACE
15 namespace internal {
16
17 template <class Char> class formatbuf : public std::basic_streambuf<Char> {
18 private:
19 using int_type = typename std::basic_streambuf<Char>::int_type;
20 using traits_type = typename std::basic_streambuf<Char>::traits_type;
21
22 buffer<Char>& buffer_;
23
24 public:
formatbuf(buffer<Char> & buf)25 formatbuf(buffer<Char>& buf) : buffer_(buf) {}
26
27 protected:
28 // The put-area is actually always empty. This makes the implementation
29 // simpler and has the advantage that the streambuf and the buffer are always
30 // in sync and sputc never writes into uninitialized memory. The obvious
31 // disadvantage is that each call to sputc always results in a (virtual) call
32 // to overflow. There is no disadvantage here for sputn since this always
33 // results in a call to xsputn.
34
35 int_type overflow(int_type ch = traits_type::eof()) FMT_OVERRIDE {
36 if (!traits_type::eq_int_type(ch, traits_type::eof()))
37 buffer_.push_back(static_cast<Char>(ch));
38 return ch;
39 }
40
xsputn(const Char * s,std::streamsize count)41 std::streamsize xsputn(const Char* s, std::streamsize count) FMT_OVERRIDE {
42 buffer_.append(s, s + count);
43 return count;
44 }
45 };
46
47 template <typename Char> struct test_stream : std::basic_ostream<Char> {
48 private:
49 // Hide all operator<< from std::basic_ostream<Char>.
50 void_t<> operator<<(null<>);
51 void_t<> operator<<(const Char*);
52
53 template <typename T, FMT_ENABLE_IF(std::is_convertible<T, int>::value &&
54 !std::is_enum<T>::value)>
55 void_t<> operator<<(T);
56 };
57
58 // Checks if T has a user-defined operator<< (e.g. not a member of
59 // std::ostream).
60 template <typename T, typename Char> class is_streamable {
61 private:
62 template <typename U>
63 static bool_constant<!std::is_same<decltype(std::declval<test_stream<Char>&>()
64 << std::declval<U>()),
65 void_t<>>::value>
66 test(int);
67
68 template <typename> static std::false_type test(...);
69
70 using result = decltype(test<T>(0));
71
72 public:
73 static const bool value = result::value;
74 };
75
76 // Write the content of buf to os.
77 template <typename Char>
write(std::basic_ostream<Char> & os,buffer<Char> & buf)78 void write(std::basic_ostream<Char>& os, buffer<Char>& buf) {
79 const Char* buf_data = buf.data();
80 using unsigned_streamsize = std::make_unsigned<std::streamsize>::type;
81 unsigned_streamsize size = buf.size();
82 unsigned_streamsize max_size = to_unsigned(max_value<std::streamsize>());
83 do {
84 unsigned_streamsize n = size <= max_size ? size : max_size;
85 os.write(buf_data, static_cast<std::streamsize>(n));
86 buf_data += n;
87 size -= n;
88 } while (size != 0);
89 }
90
91 template <typename Char, typename T>
92 void format_value(buffer<Char>& buf, const T& value,
93 locale_ref loc = locale_ref()) {
94 formatbuf<Char> format_buf(buf);
95 std::basic_ostream<Char> output(&format_buf);
96 if (loc) output.imbue(loc.get<std::locale>());
97 output.exceptions(std::ios_base::failbit | std::ios_base::badbit);
98 output << value;
99 buf.resize(buf.size());
100 }
101
102 // Formats an object of type T that has an overloaded ostream operator<<.
103 template <typename T, typename Char>
104 struct fallback_formatter<T, Char, enable_if_t<is_streamable<T, Char>::value>>
105 : formatter<basic_string_view<Char>, Char> {
106 template <typename Context>
107 auto format(const T& value, Context& ctx) -> decltype(ctx.out()) {
108 basic_memory_buffer<Char> buffer;
109 format_value(buffer, value, ctx.locale());
110 basic_string_view<Char> str(buffer.data(), buffer.size());
111 return formatter<basic_string_view<Char>, Char>::format(str, ctx);
112 }
113 };
114 } // namespace internal
115
116 template <typename Char>
117 void vprint(std::basic_ostream<Char>& os, basic_string_view<Char> format_str,
118 basic_format_args<buffer_context<Char>> args) {
119 basic_memory_buffer<Char> buffer;
120 internal::vformat_to(buffer, format_str, args);
121 internal::write(os, buffer);
122 }
123
124 /**
125 \rst
126 Prints formatted data to the stream *os*.
127
128 **Example**::
129
130 fmt::print(cerr, "Don't {}!", "panic");
131 \endrst
132 */
133 template <typename S, typename... Args,
134 typename Char = enable_if_t<internal::is_string<S>::value, char_t<S>>>
135 void print(std::basic_ostream<Char>& os, const S& format_str, Args&&... args) {
136 vprint(os, to_string_view(format_str),
137 {internal::make_args_checked<Args...>(format_str, args...)});
138 }
139 FMT_END_NAMESPACE
140
141 #endif // FMT_OSTREAM_H_
142