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construct/include/ircd/fmt.h

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6.6 KiB
C++

// Matrix Construct
//
// Copyright (C) Matrix Construct Developers, Authors & Contributors
// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice is present in all copies. The
// full license for this software is available in the LICENSE file.
#pragma once
#define HAVE_IRCD_FMT_H
/// Typesafe format strings from formal grammars & standard RTTI
namespace ircd::fmt
{
IRCD_EXCEPTION(ircd::error, error);
IRCD_PANICKING(error, invalid_format);
IRCD_PANICKING(error, invalid_type);
IRCD_PANICKING(error, illegal);
struct sprintf;
struct vsprintf;
struct snprintf;
struct vsnprintf;
struct snstringf;
struct vsnstringf;
struct literal_snstringf;
struct literal_snstringf__max;
template<size_t MAX> struct bsprintf;
using arg = std::tuple<const void *, const std::type_index &>;
literal_snstringf operator ""_snstringf(const char *text, const size_t len);
literal_snstringf__max operator,(const literal_snstringf, const ulong max);
template<class... args> std::string operator,(const literal_snstringf__max, args&&...);
}
namespace ircd
{
using fmt::operator ""_snstringf;
}
/// Typesafe snprintf() from formal grammar and RTTI.
///
/// This function accepts a format string and a variable number of arguments
/// composing formatted null-terminated output in the provided output buffer.
/// The format string is compliant with standard snprintf() (TODO: not yet).
/// The type information of the arguments is grabbed from the variadic template
/// and references are passed to the formal output grammars. This means you can
/// pass an std::string directly without calling c_str(), as well as pass a
/// non-null-terminated string_view safely.
///
class ircd::fmt::snprintf
{
window_buffer out; // Window on the output buffer.
const_buffer fmt; // Current running position in the fmtstr.
short idx; // Keeps count of the args for better err msgs
bool finished() const noexcept;
size_t remaining() const noexcept;
size_t consumed() const { return out.consumed(); }
string_view completed() const { return out.completed(); }
void append(const string_view &);
void argument(const arg &);
protected:
IRCD_OVERLOAD(internal)
snprintf(internal_t, const mutable_buffer &, const string_view &, const va_rtti &);
public:
operator ssize_t() const { return consumed(); }
operator string_view() const { return completed(); }
template<class... Args>
snprintf(char *const &buf,
const size_t &max,
const string_view &fmt,
Args&&... args)
:snprintf
{
internal, mutable_buffer{buf, max}, fmt, va_rtti{std::forward<Args>(args)...}
}{}
};
/// Same as snprintf() where n= is deduced by the buffer size argument
///
struct ircd::fmt::sprintf
:snprintf
{
template<class... Args>
sprintf(const mutable_buffer &buf,
const string_view &fmt,
Args&&... args)
:snprintf
{
internal, buf, fmt, va_rtti{std::forward<Args>(args)...}
}{}
};
/// A complement to fmt::snprintf() accepting an already-made va_rtti.
///
/// This function has no variadic template; instead it accepts the type
/// which would be composed by such a variadic template called
/// ircd::va_rtti directly.
///
/// ircd::va_rtti is a lightweight pairing of argument pointers to runtime
/// type indexes. ircd::va_rtti is not a template itself because its purpose
/// is to bring this type information out of the header files to where the
/// grammar is instantiated.
///
struct ircd::fmt::vsnprintf
:snprintf
{
vsnprintf(char *const &buf,
const size_t &max,
const string_view &fmt,
const va_rtti &ap)
:snprintf
{
internal, mutable_buffer{buf, max}, fmt, ap
}{}
};
/// Same as vsnprintf() where n is deduced from the buffer size.
///
struct ircd::fmt::vsprintf
:snprintf
{
vsprintf(const mutable_buffer &buf,
const string_view &fmt,
const va_rtti &ap)
:snprintf
{
internal, buf, fmt, ap
}{}
};
/// Allocates a buffer (std::string) of size for the result.
///
/// see snstringf() for vararg format overload.
struct ircd::fmt::vsnstringf
:std::string
{
vsnstringf(const size_t &max,
const string_view &fmt,
const va_rtti &ap)
:std::string
{
ircd::string(max, [&fmt, &ap]
(const mutable_buffer &buf) -> string_view
{
return vsprintf
{
buf, fmt, ap
};
})
}{}
};
/// Allocates a buffer (std::string) of size for the result.
///
/// Note: that OR'ing the size with ircd::SHRINK_TO_FIT constant will trigger
/// a standard string re-evaluation to determine if the final result string
/// should be transferred to a smaller buffer.
struct ircd::fmt::snstringf
:vsnstringf
{
template<class... args>
snstringf(const size_t &max,
const string_view &fmt,
args&&... a)
:vsnstringf
{
max, fmt, va_rtti{std::forward<args>(a)...}
}{}
};
/// Efficient in-place buffer convenience template.
///
/// This is an object which contains the result buffer internally. The size
/// of that buffer is given in the template parameter. This is clean and
/// efficient for basic format string operations on the stack while avoiding
/// the clutter of buffer statements and mgmt.
template<size_t MAX>
struct ircd::fmt::bsprintf
:snprintf
,string_view
{
char buf[MAX];
template<class... args>
bsprintf(const string_view &fmt,
args&&... a)
:snprintf
{
internal, buf, fmt, va_rtti{std::forward<args>(a)...}
}
,string_view
{
buf, size_t(static_cast<snprintf &>(*this))
}{}
};
/// Experimental typedef for format strings.
struct ircd::fmt::literal_snstringf
{
string_view format;
};
/// Experimental typedef for format strings.
struct ircd::fmt::literal_snstringf__max
{
literal_snstringf format;
size_t max;
};
template<class... args>
inline std::string
ircd::fmt::operator,(const literal_snstringf__max format,
args&&... a)
{
return fmt::snstringf
{
format.max, format.format.format, std::forward<args>(a)...
};
}
inline ircd::fmt::literal_snstringf__max
ircd::fmt::operator,(const literal_snstringf format,
const ulong max)
{
return literal_snstringf__max
{
format, max
};
}
inline ircd::fmt::literal_snstringf
ircd::fmt::operator ""_snstringf(const char *const format,
const size_t len)
{
return literal_snstringf
{
string_view
{
format, len
}
};
}