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fmt::format<Char, T> inefficiency #92

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This commit is contained in:
Michael Kasperovich 2015-11-17 20:06:11 +03:00
parent d9e0f5c04e
commit 5343eab4c8
1 changed files with 42 additions and 8 deletions
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50
format.h
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@ -38,6 +38,7 @@
#include <stdexcept>
#include <string>
#include <map>
#include <ostream>
#ifndef FMT_USE_IOSTREAMS
# define FMT_USE_IOSTREAMS 1
@ -478,6 +479,11 @@ class Buffer {
T &operator[](std::size_t index) { return ptr_[index]; }
const T &operator[](std::size_t index) const { return ptr_[index]; }
template<class Elem, class Traits = std::char_traits<Elem> >
friend class basic_formatbuf;
};
template <typename T>
@ -2027,6 +2033,11 @@ class BasicWriter {
*/
std::size_t size() const { return buffer_.size(); }
/**
Returns underlying buffer.
*/
Buffer<Char>& buffer() const { return buffer_; }
/**
Returns a pointer to the output buffer content. No terminating null
character is appended.
@ -2628,16 +2639,39 @@ class BasicArrayWriter : public BasicWriter<Char> {
typedef BasicArrayWriter<char> ArrayWriter;
typedef BasicArrayWriter<wchar_t> WArrayWriter;
template<class Elem, class Traits = std::char_traits<Elem> >
class basic_formatbuf : public std::basic_streambuf<Elem, Traits> {
typedef typename std::basic_streambuf<Elem, Traits>::int_type int_type;
Buffer<Elem>& buffer_;
public:
basic_formatbuf(BasicFormatter<Elem> &formatter) : buffer_(formatter.writer().buffer()) {
setp(buffer_.ptr_, buffer_.ptr_ + buffer_.size_, buffer_.ptr_ + buffer_.capacity_);
}
virtual int_type overflow(int_type _Meta = Traits::eof()) {
buffer_.grow(buffer_.capacity_ * 2);
setp(buffer_.ptr_, buffer_.ptr_ + buffer_.size_, buffer_.ptr_ + buffer_.capacity_);
return traits_type::to_int_type(*pptr());
}
int_type flush() {
buffer_.size_ = pptr() - pbase();
return traits_type::to_int_type(*pptr());
}
};
// Formats a value.
template <typename Char, typename T>
void format(BasicFormatter<Char> &f, const Char *&format_str, const T &value) {
std::basic_ostringstream<Char> os;
os << value;
std::basic_string<Char> str = os.str();
internal::Arg arg = internal::MakeValue<Char>(str);
arg.type = static_cast<internal::Arg::Type>(
internal::MakeValue<Char>::type(str));
format_str = f.format(format_str, arg);
void format(BasicFormatter<Char> &formatter, const Char *&format_str, const T &value) {
basic_formatbuf<Char> format_buf(formatter);
std::basic_ostream<Char> output(&format_buf);
output << value;
format_buf.flush();
}
// Reports a system error without throwing an exception.