157 lines
4.8 KiB
C++
157 lines
4.8 KiB
C++
// Formatting library for C++ - std::ostream support
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//
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// Copyright (c) 2012 - 2016, 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 "format.h"
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#include <ostream>
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FMT_BEGIN_NAMESPACE
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namespace internal {
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template <class Char>
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class formatbuf : public std::basic_streambuf<Char> {
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private:
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typedef typename std::basic_streambuf<Char>::int_type int_type;
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typedef typename std::basic_streambuf<Char>::traits_type traits_type;
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basic_buffer<Char> &buffer_;
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public:
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formatbuf(basic_buffer<Char> &buffer) : buffer_(buffer) {}
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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>
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struct test_stream : std::basic_ostream<Char> {
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private:
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struct null;
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// Hide all operator<< from std::basic_ostream<Char>.
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void operator<<(null);
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};
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// Checks if T has a user-defined operator<< (e.g. not a member of std::ostream).
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template <typename T, typename Char>
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class is_streamable {
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private:
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template <typename U>
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static decltype(
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internal::declval<test_stream<Char>&>()
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<< internal::declval<U>(), std::true_type()) test(int);
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template <typename>
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static std::false_type test(...);
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typedef decltype(test<T>(0)) result;
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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, basic_buffer<Char> &buf) {
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const Char *data = buf.data();
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typedef std::make_unsigned<std::streamsize>::type UnsignedStreamSize;
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UnsignedStreamSize size = buf.size();
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UnsignedStreamSize max_size =
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internal::to_unsigned((std::numeric_limits<std::streamsize>::max)());
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do {
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UnsignedStreamSize n = size <= max_size ? size : max_size;
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os.write(data, static_cast<std::streamsize>(n));
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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(basic_buffer<Char> &buffer, const T &value) {
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internal::formatbuf<Char> format_buf(buffer);
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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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buffer.resize(buffer.size());
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}
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} // namespace internal
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// Disable conversion to int if T has an overloaded operator<< which is a free
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// function (not a member of std::ostream).
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template <typename T, typename Char>
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struct convert_to_int<T, Char, void> {
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static const bool value =
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convert_to_int<T, Char, int>::value &&
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!internal::is_streamable<T, Char>::value;
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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 formatter<T, Char,
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typename std::enable_if<
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internal::is_streamable<T, Char>::value &&
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!internal::format_type<
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typename buffer_context<Char>::type, T>::value>::type>
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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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internal::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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template <typename Char>
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inline void vprint(std::basic_ostream<Char> &os,
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basic_string_view<Char> format_str,
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basic_format_args<typename buffer_context<Char>::type> args) {
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basic_memory_buffer<Char> buffer;
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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... Args>
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inline void print(std::ostream &os, string_view format_str,
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const Args & ... args) {
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vprint<char>(os, format_str, make_format_args<format_context>(args...));
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}
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template <typename... Args>
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inline void print(std::wostream &os, wstring_view format_str,
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const Args & ... args) {
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vprint<wchar_t>(os, format_str, make_format_args<wformat_context>(args...));
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}
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FMT_END_NAMESPACE
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#endif // FMT_OSTREAM_H_
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