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
13 #include "format.h"
14
15 FMT_BEGIN_NAMESPACE
16
17 template <typename Char> class basic_printf_parse_context;
18 template <typename OutputIt, typename Char> class basic_printf_context;
19
20 namespace detail {
21
22 template <class Char> class formatbuf : public std::basic_streambuf<Char> {
23 private:
24 using int_type = typename std::basic_streambuf<Char>::int_type;
25 using traits_type = typename std::basic_streambuf<Char>::traits_type;
26
27 buffer<Char>& buffer_;
28
29 public:
formatbuf(buffer<Char> & buf)30 formatbuf(buffer<Char>& buf) : buffer_(buf) {}
31
32 protected:
33 // The put-area is actually always empty. This makes the implementation
34 // simpler and has the advantage that the streambuf and the buffer are always
35 // in sync and sputc never writes into uninitialized memory. The obvious
36 // disadvantage is that each call to sputc always results in a (virtual) call
37 // to overflow. There is no disadvantage here for sputn since this always
38 // results in a call to xsputn.
39
40 int_type overflow(int_type ch = traits_type::eof()) FMT_OVERRIDE {
41 if (!traits_type::eq_int_type(ch, traits_type::eof()))
42 buffer_.push_back(static_cast<Char>(ch));
43 return ch;
44 }
45
xsputn(const Char * s,std::streamsize count)46 std::streamsize xsputn(const Char* s, std::streamsize count) FMT_OVERRIDE {
47 buffer_.append(s, s + count);
48 return count;
49 }
50 };
51
52 struct converter {
53 template <typename T, FMT_ENABLE_IF(is_integral<T>::value)> converter(T);
54 };
55
56 template <typename Char> struct test_stream : std::basic_ostream<Char> {
57 private:
58 void_t<> operator<<(converter);
59 };
60
61 // Hide insertion operators for built-in types.
62 template <typename Char, typename Traits>
63 void_t<> operator<<(std::basic_ostream<Char, Traits>&, Char);
64 template <typename Char, typename Traits>
65 void_t<> operator<<(std::basic_ostream<Char, Traits>&, char);
66 template <typename Traits>
67 void_t<> operator<<(std::basic_ostream<char, Traits>&, char);
68 template <typename Traits>
69 void_t<> operator<<(std::basic_ostream<char, Traits>&, signed char);
70 template <typename Traits>
71 void_t<> operator<<(std::basic_ostream<char, Traits>&, unsigned char);
72
73 // Checks if T has a user-defined operator<< (e.g. not a member of
74 // std::ostream).
75 template <typename T, typename Char> class is_streamable {
76 private:
77 template <typename U>
78 static bool_constant<!std::is_same<decltype(std::declval<test_stream<Char>&>()
79 << std::declval<U>()),
80 void_t<>>::value>
81 test(int);
82
83 template <typename> static std::false_type test(...);
84
85 using result = decltype(test<T>(0));
86
87 public:
88 static const bool value = result::value;
89 };
90
91 // Write the content of buf to os.
92 template <typename Char>
write_buffer(std::basic_ostream<Char> & os,buffer<Char> & buf)93 void write_buffer(std::basic_ostream<Char>& os, buffer<Char>& buf) {
94 const Char* buf_data = buf.data();
95 using unsigned_streamsize = std::make_unsigned<std::streamsize>::type;
96 unsigned_streamsize size = buf.size();
97 unsigned_streamsize max_size = to_unsigned(max_value<std::streamsize>());
98 do {
99 unsigned_streamsize n = size <= max_size ? size : max_size;
100 os.write(buf_data, static_cast<std::streamsize>(n));
101 buf_data += n;
102 size -= n;
103 } while (size != 0);
104 }
105
106 template <typename Char, typename T>
107 void format_value(buffer<Char>& buf, const T& value,
108 locale_ref loc = locale_ref()) {
109 formatbuf<Char> format_buf(buf);
110 std::basic_ostream<Char> output(&format_buf);
111 #if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
112 if (loc) output.imbue(loc.get<std::locale>());
113 #endif
114 output << value;
115 output.exceptions(std::ios_base::failbit | std::ios_base::badbit);
116 buf.try_resize(buf.size());
117 }
118
119 // Formats an object of type T that has an overloaded ostream operator<<.
120 template <typename T, typename Char>
121 struct fallback_formatter<T, Char, enable_if_t<is_streamable<T, Char>::value>>
122 : private formatter<basic_string_view<Char>, Char> {
123 FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
124 -> decltype(ctx.begin()) {
125 return formatter<basic_string_view<Char>, Char>::parse(ctx);
126 }
127 template <typename ParseCtx,
128 FMT_ENABLE_IF(std::is_same<
129 ParseCtx, basic_printf_parse_context<Char>>::value)>
130 auto parse(ParseCtx& ctx) -> decltype(ctx.begin()) {
131 return ctx.begin();
132 }
133
134 template <typename OutputIt>
135 auto format(const T& value, basic_format_context<OutputIt, Char>& ctx)
136 -> OutputIt {
137 basic_memory_buffer<Char> buffer;
138 format_value(buffer, value, ctx.locale());
139 basic_string_view<Char> str(buffer.data(), buffer.size());
140 return formatter<basic_string_view<Char>, Char>::format(str, ctx);
141 }
142 template <typename OutputIt>
143 auto format(const T& value, basic_printf_context<OutputIt, Char>& ctx)
144 -> OutputIt {
145 basic_memory_buffer<Char> buffer;
146 format_value(buffer, value, ctx.locale());
147 return std::copy(buffer.begin(), buffer.end(), ctx.out());
148 }
149 };
150 } // namespace detail
151
152 template <typename Char>
153 void vprint(std::basic_ostream<Char>& os, basic_string_view<Char> format_str,
154 basic_format_args<buffer_context<type_identity_t<Char>>> args) {
155 basic_memory_buffer<Char> buffer;
156 detail::vformat_to(buffer, format_str, args);
157 detail::write_buffer(os, buffer);
158 }
159
160 /**
161 \rst
162 Prints formatted data to the stream *os*.
163
164 **Example**::
165
166 fmt::print(cerr, "Don't {}!", "panic");
167 \endrst
168 */
169 template <typename S, typename... Args,
170 typename Char = enable_if_t<detail::is_string<S>::value, char_t<S>>>
171 void print(std::basic_ostream<Char>& os, const S& format_str, Args&&... args) {
172 vprint(os, to_string_view(format_str),
173 fmt::make_args_checked<Args...>(format_str, args...));
174 }
175 FMT_END_NAMESPACE
176
177 #endif // FMT_OSTREAM_H_
178