140 lines
4.4 KiB
C++
140 lines
4.4 KiB
C++
// Formatting library for C++ - std::ostream support
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//
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// Copyright (c) 2012 - present, Victor Zverovich
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// All rights reserved.
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//
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// For the license information refer to format.h.
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#ifndef FMT_OSTREAM_H_
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#define FMT_OSTREAM_H_
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#include <ostream>
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#include "format.h"
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FMT_BEGIN_NAMESPACE
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namespace internal {
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template <class Char> class formatbuf : public std::basic_streambuf<Char> {
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private:
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using int_type = typename std::basic_streambuf<Char>::int_type;
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using traits_type = typename std::basic_streambuf<Char>::traits_type;
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buffer<Char>& buffer_;
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public:
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formatbuf(buffer<Char>& buf) : buffer_(buf) {}
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protected:
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// The put-area is actually always empty. This makes the implementation
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// simpler and has the advantage that the streambuf and the buffer are always
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// in sync and sputc never writes into uninitialized memory. The obvious
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// disadvantage is that each call to sputc always results in a (virtual) call
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// to overflow. There is no disadvantage here for sputn since this always
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// results in a call to xsputn.
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int_type overflow(int_type ch = traits_type::eof()) FMT_OVERRIDE {
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if (!traits_type::eq_int_type(ch, traits_type::eof()))
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buffer_.push_back(static_cast<Char>(ch));
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return ch;
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}
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std::streamsize xsputn(const Char* s, std::streamsize count) FMT_OVERRIDE {
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buffer_.append(s, s + count);
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return count;
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}
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};
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template <typename Char> struct test_stream : std::basic_ostream<Char> {
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private:
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// Hide all operator<< from std::basic_ostream<Char>.
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void_t<> operator<<(null<>);
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void_t<> operator<<(const Char*);
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template <typename T, FMT_ENABLE_IF(std::is_convertible<T, int>::value &&
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!std::is_enum<T>::value)>
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void_t<> operator<<(T);
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};
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// Checks if T has a user-defined operator<< (e.g. not a member of
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// std::ostream).
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template <typename T, typename Char> class is_streamable {
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private:
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template <typename U>
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static bool_constant<!std::is_same<decltype(std::declval<test_stream<Char>&>()
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<< std::declval<U>()),
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void_t<>>::value>
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test(int);
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template <typename> static std::false_type test(...);
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using result = decltype(test<T>(0));
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public:
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static const bool value = result::value;
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};
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// Write the content of buf to os.
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template <typename Char>
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void write(std::basic_ostream<Char>& os, buffer<Char>& buf) {
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const Char* buf_data = buf.data();
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using unsigned_streamsize = std::make_unsigned<std::streamsize>::type;
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unsigned_streamsize size = buf.size();
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unsigned_streamsize max_size = to_unsigned(max_value<std::streamsize>());
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do {
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unsigned_streamsize n = size <= max_size ? size : max_size;
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os.write(buf_data, static_cast<std::streamsize>(n));
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buf_data += n;
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size -= n;
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} while (size != 0);
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}
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template <typename Char, typename T>
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void format_value(buffer<Char>& buf, const T& value) {
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formatbuf<Char> format_buf(buf);
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std::basic_ostream<Char> output(&format_buf);
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output.exceptions(std::ios_base::failbit | std::ios_base::badbit);
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output << value;
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buf.resize(buf.size());
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}
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// Formats an object of type T that has an overloaded ostream operator<<.
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template <typename T, typename Char>
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struct fallback_formatter<T, Char, enable_if_t<is_streamable<T, Char>::value>>
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: formatter<basic_string_view<Char>, Char> {
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template <typename Context>
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auto format(const T& value, Context& ctx) -> decltype(ctx.out()) {
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basic_memory_buffer<Char> buffer;
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format_value(buffer, value);
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basic_string_view<Char> str(buffer.data(), buffer.size());
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return formatter<basic_string_view<Char>, Char>::format(str, ctx);
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}
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};
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} // namespace internal
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template <typename Char>
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void vprint(std::basic_ostream<Char>& os, basic_string_view<Char> format_str,
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basic_format_args<buffer_context<Char>> args) {
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basic_memory_buffer<Char> buffer;
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internal::vformat_to(buffer, format_str, args);
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internal::write(os, buffer);
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}
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/**
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\rst
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Prints formatted data to the stream *os*.
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**Example**::
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fmt::print(cerr, "Don't {}!", "panic");
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\endrst
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*/
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template <typename S, typename... Args,
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typename Char = enable_if_t<internal::is_string<S>::value, char_t<S>>>
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void print(std::basic_ostream<Char>& os, const S& format_str, Args&&... args) {
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vprint(os, to_string_view(format_str),
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{internal::make_args_checked<Args...>(format_str, args...)});
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}
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FMT_END_NAMESPACE
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#endif // FMT_OSTREAM_H_
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