Charconv utilities

Lightweight, very fast generic type-safe wrappers for converting individual values to/from strings. More...

Modules
	Get number of digits
	Write with known number of digits
	Writes a value without checking the buffer length with regards to the required number of digits to encode the value.
	Write a value
	Writes a value without checking the buffer length decimal number – but asserting.
	Read a value
	itoa: signed to chars
	utoa: unsigned to chars
	atoi: chars to signed
	atou: chars to unsigned
	overflows: does a number string overflow a type
	ftoa: float32 to chars
	dtoa: float64 to chars
	atof: chars to float32
	atod: chars to float64
	xtoa: generic value to chars
	Dispatches to the most appropriate and efficient conversion function.
	atox: generic chars to value
	Dispatches to the most appropriate and efficient conversion function.
	to_chars: generalized chars to value
	Convert the given value, writing into the string.
	from_chars: generalized chars to value
	Read a value from the string, which must be trimmed to the value (ie, no leading/trailing whitespace).

Enumerations
enum	c4::RealFormat_e : char { c4::FTOA_FLOAT = 'f', c4::FTOA_SCIENT = 'e', c4::FTOA_FLEX = 'g', c4::FTOA_HEXA = 'a' }

Detailed Description

Lightweight, very fast generic type-safe wrappers for converting individual values to/from strings.

These are the main generic functions:

• to_chars: generalized chars to value and its alias xtoa(): implemented by calling itoa() / utoa() / ftoa() / dtoa() (or generically xtoa())
• from_chars: generalized chars to value and its alias atox(): implemented by calling atoi() / atou() / atof() / atod() (or generically atox())
• to_chars_sub()
• from_chars_first()
• xtoa() and atox() are implemented in terms of write_dec() / read_dec() et al (see Write a value / Read a value)

And also some modest brag is in order: these functions are really fast: faster even than C++17 std::to_chars() and std::to_chars(), and many dozens of times faster than the iostream abominations.

For example, here are some benchmark comparisons for from_chars: generalized chars to value (link leads to the main project README, where these results are shown more systematically).

atox,int64_t

g++12, linux	Visual Studio 2019
html windows-x86_64-vs2019-Release-c4core-bm-charconv-atox-mega_bytes_per_second-i64.png

xtoa,int64_t

g++12, linux	Visual Studio 2019
html windows-x86_64-vs2019-Release-c4core-bm-charconv-xtoa-mega_bytes_per_second-i64.png

To parse floating point, c4core uses fastfloat, which is extremely fast, by an even larger factor:

atox,float

g++12, linux	Visual Studio 2019
html windows-x86_64-vs2019-Release-c4core-bm-charconv-atof-mega_bytes_per_second-float.png

Enumeration Type Documentation

enum c4::RealFormat_e : char

Warning

Use only the symbol. Do not rely on the type or naked value of this enum.

Enumerator
FTOA_FLOAT	print the real number in floating point format (like f)
FTOA_SCIENT	print the real number in scientific format (like e)
FTOA_FLEX	print the real number in flexible format (like g)
FTOA_HEXA	print the real number in hexadecimal format (like a)

Definition at line 192 of file charconv.hpp.

             : char {
    /** print the real number in floating point format (like %f) */
    FTOA_FLOAT = 'f',
    /** print the real number in scientific format (like %e) */
    FTOA_SCIENT = 'e',
    /** print the real number in flexible format (like %g) */
    FTOA_FLEX = 'g',
    /** print the real number in hexadecimal format (like %a) */
    FTOA_HEXA = 'a',
} RealFormat_e;