notcurses_metric(3)

nick black

v2.2.8

NAME

notcurses_metric - fixed-width numeric output with metric suffixes

SYNOPSIS

#include <notcurses/notcurses.h>

#define PREFIXCOLUMNS 7
#define IPREFIXCOLUMNS 8
#define BPREFIXCOLUMNS 9
#define PREFIXSTRLEN (PREFIXCOLUMNS + 1)
#define IPREFIXSTRLEN (IPREFIXCOLUMNS + 1)
#define BPREFIXSTRLEN (BPREFIXCOLUMNS + 1)
#define NCMETRICFWIDTH(x, cols) ((int)(strlen(x) - ncstrwidth(x) + (cols)))
#define PREFIXFMT(x) NCMETRICFWIDTH((x), PREFIXCOLUMNS), (x)
#define IPREFIXFMT(x) NCMETRIXFWIDTH((x), IPREFIXCOLUMNS), (x)
#define BPREFIXFMT(x) NCMETRICFWIDTH((x), BPREFIXCOLUMNS), (x)

const char* ncmetric(uintmax_t val, uintmax_t decimal, char* buf, int omitdec, unsigned mult, int uprefix);

static inline const char* qprefix(uintmax_t val, uintmax_t decimal, char* buf, int omitdec);

static inline const char* iprefix(uintmax_t val, uintmax_t decimal, char* buf, int omitdec);

static inline const char* bprefix(uintmax_t val, uintmax_t decimal, char* buf, int omitdec);

DESCRIPTION

ncmetric (and the helper wrappers qprefix and bprefix) accept very large (or very small) non-negative numbers, and prepare formatted output of a maximum width using metric suffixes. The suffix can represent arbitrary amounts of growth, but is designed for 1000 (PREFIX) or 1024 (IPREFIX). 1024 is used for "digital units of information", i.e. kibibytes and gibibits. ncmetric supports the large suffixes KMGTPEZY (Kilo, Mega, Giga, Tera, Peta, Exa, Zetta, and Yotta) and the small suffixes mµnpfazy (Milli, Micro, Nano, Pico, Femto, Atto, Zepto, and Yocto). This covers the range 1e24 (one septillion) through 1e-24, sufficing for all possible values of a 64-bit uintmax_t.

val is the value being output, having been scaled by decimal. decimal will typically be 1; to represent values less than 1, decimal should be larger than val. The output will be written to buf, which must be at least:

Three helper functions are provided to simplify these common cases:

// Mega, kilo, gigafoo. Use PREFIXSTRLEN + 1 and PREFIXCOLUMNS.
static inline const char*
qprefix(uintmax_t val, uintmax_t decimal, char* buf, int omitdec){
  return ncmetric(val, decimal, buf, omitdec, 1000, '\0');
}

// Mibi, kebi, gibibytes sans 'i' suffix. Use IPREFIXSTRLEN + 1.
static inline const char*
iprefix(uintmax_t val, uintmax_t decimal, char* buf, int omitdec){
  return ncmetric(val, decimal, buf, omitdec, 1024, '\0');
}

// Mibi, kebi, gibibytes. Use BPREFIXSTRLEN + 1 and BPREFIXCOLUMNS.
static inline const char*
bprefix(uintmax_t val, uintmax_t decimal, char* buf, int omitdec){
  return ncmetric(val, decimal, buf, omitdec, 1024, 'i');
}

If omitdec is not zero, the decimal point and mantissa will be omitted if all digits to be displayed would be zero. The decimal point takes the current locale into account (see setlocale(3) and localeconv(3)). mult is the relative multiple for each suffix. uprefix, if not zero, will be used as a suffix following any metric suffix.

The maximum number of columns is not directly related to the maximum number of bytes, since Unicode doesn't necessarily map to single-byte characters (including the 'µ' micro suffix). The corresponding defines for maximum column length are:

In general, the maximum-width output will take the form CCC.mmMu, where C are digits of the characteristic (up to ceil(log10(mult)) digits), the decimal point follows, m are digits of the mantissa (up to 2), M is the metric suffix, and u is the uprefix. The minimum-width output will take the form C. This minimal form can occur if omitdec is non-zero and a single-column value such as 5 is passed for val.

Three more defines are provided to simplify formatted fixed-width output using the results of ncmetric. Each of these macros accepts a character buffer holding the result of the call, and expand to two arguments:

These can be used in e.g. the following ungainly fashion:

**ncplane_printf(n, "%*s", PREFIXFMT(buf));**

to ensure that the output is always PREFIXCOLUMNS wide.

RETURN VALUES

NULL if input parameters were invalid. Otherwise, a pointer to buf, filled in with the formatted output.

EXAMPLES

ncmetric(0, 1, buf, 0, 1000, '\0'): "0.00".

ncmetric(0, 1, buf, 1, 1000, '\0'): "0".

ncmetric(1023, 1, buf, 1, 1000, '\0'): "1.02K".

ncmetric(1023, 1, buf, 1, 1024, 'i'): "1023".

ncmetric(1024, 1, buf, 1, 1024, 'i'): "1Ki".

ncmetric(4096, 1, buf, 0, 1024, 'i'): "4.00Ki".

ncmetric(0x7fffffffffffffff, 1, buf, 0, 1000, '\0'): "9.22E".

ncmetric(0xffffffffffffffff, 1, buf, 0, 1000, '\0'): "18.45E".

BUGS

This function is difficult to understand.

SEE ALSO

localeconv(3), notcurses(3), notcurses_output(3), setlocale(3)