notcurses_metric(3)

1notcurses_metric(3)                                        notcurses_metric(3)
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NAME

6       notcurses_metric - fixed-width numeric output with metric suffixes
7

SYNOPSIS

9       #include <notcurses/notcurses.h>
10
11              #define PREFIXCOLUMNS 7
12              #define IPREFIXCOLUMNS 8
13              #define BPREFIXCOLUMNS 9
14              #define PREFIXSTRLEN (PREFIXCOLUMNS + 1)
15              #define IPREFIXSTRLEN (IPREFIXCOLUMNS + 1)
16              #define BPREFIXSTRLEN (BPREFIXCOLUMNS + 1)
17              #define NCMETRICFWIDTH(x, cols) ((int)(strlen(x) - ncstrwidth(x) + (cols)))
18              #define PREFIXFMT(x) NCMETRICFWIDTH((x), PREFIXCOLUMNS), (x)
19              #define IPREFIXFMT(x) NCMETRIXFWIDTH((x), IPREFIXCOLUMNS), (x)
20              #define BPREFIXFMT(x) NCMETRICFWIDTH((x), BPREFIXCOLUMNS), (x)
21
22       const  char*  ncmetric(uintmax_t val, uintmax_t decimal, char* buf, int
23       omitdec, unsigned mult, int uprefix);
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25       static inline const char*  qprefix(uintmax_t  val,  uintmax_t  decimal,
26       char* buf, int omitdec);
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28       static  inline  const  char*  iprefix(uintmax_t val, uintmax_t decimal,
29       char* buf, int omitdec);
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31       static inline const char*  bprefix(uintmax_t  val,  uintmax_t  decimal,
32       char* buf, int omitdec);
33

DESCRIPTION

35       ncmetric  (and  the  helper  wrappers  qprefix and bprefix) accept very
36       large (or very small) non-negative numbers, and prepare formatted  out‐
37       put of a maximum width using metric suffixes.  The suffix can represent
38       arbitrary amounts of growth, but is designed for 1000 (PREFIX) or  1024
39       (IPREFIX).   1024  is  used  for  "digital  units of information", i.e.
40       kibibytes and gibibits.  ncmetric supports the large suffixes  KMGTPEZY
41       (Kilo,  Mega,  Giga,  Tera,  Peta, Exa, Zetta, and Yotta) and the small
42       suffixes mµnpfazy (Milli, Micro, Nano, Pico, Femto,  Atto,  Zepto,  and
43       Yocto).   This  covers  the  range 1e24 (one septillion) through 1e-24,
44       sufficing for all possible values of a 64-bit uintmax_t.
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46       val is the value being output, having been scaled by decimal.   decimal
47       will typically be 1; to represent values less than 1, decimal should be
48       larger than val.  The output will be written to buf, which must  be  at
49       least:
50
51       • PREFIXSTRLEN + 1 bytes for a 1000-based value
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53       • IPREFIXSTRLEN + 1 bytes for a 1024-based value
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55       • BPREFIXSTRLEN + 1 bytes for a 1024-based value with an 'i' suffix
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57       Three helper functions are provided to simplify these common cases:
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59              // Mega, kilo, gigafoo. Use PREFIXSTRLEN + 1 and PREFIXCOLUMNS.
60              static inline const char*
61              qprefix(uintmax_t val, uintmax_t decimal, char* buf, int omitdec){
62                return ncmetric(val, decimal, buf, omitdec, 1000, '\0');
63              }
64
65              // Mibi, kebi, gibibytes sans 'i' suffix. Use IPREFIXSTRLEN + 1.
66              static inline const char*
67              iprefix(uintmax_t val, uintmax_t decimal, char* buf, int omitdec){
68                return ncmetric(val, decimal, buf, omitdec, 1024, '\0');
69              }
70
71              // Mibi, kebi, gibibytes. Use BPREFIXSTRLEN + 1 and BPREFIXCOLUMNS.
72              static inline const char*
73              bprefix(uintmax_t val, uintmax_t decimal, char* buf, int omitdec){
74                return ncmetric(val, decimal, buf, omitdec, 1024, 'i');
75              }
76
77       If  omitdec is not zero, the decimal point and mantissa will be omitted
78       if all digits to be displayed would be zero.  The decimal  point  takes
79       the  current  locale into account (see setlocale(3) and localeconv(3)).
80       mult is the relative multiple for each suffix.  uprefix, if  not  zero,
81       will be used as a suffix following any metric suffix.
82
83       The  maximum  number  of columns is not directly related to the maximum
84       number of bytes, since Unicode doesn't necessarily map  to  single-byte
85       characters (including the 'µ' micro suffix).  The corresponding defines
86       for maximum column length are:
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88       • PREFIXCOLUMNS (7)
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90       • IPREFIXCOLUMNS (8)
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92       • BPREFIXCOLUMNS (9)
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94       In general, the maximum-width output will take the form CCC.mmMu, where
95       C  are  digits  of the characteristic (up to ceil(log10(mult)) digits),
96       the decimal point follows, m are digits of the mantissa (up to 2), M is
97       the metric suffix, and u is the uprefix.  The minimum-width output will
98       take the form C.  This minimal form can occur if  omitdec  is  non-zero
99       and a single-column value such as 5 is passed for val.
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101       Three  more defines are provided to simplify formatted fixed-width out‐
102       put using the results of ncmetric.  Each  of  these  macros  accepts  a
103       character  buffer holding the result of the call, and expand to two ar‐
104       guments:
105
106       • PREFIXFMT(x)
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108       • IPREFIXFMT(x)
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110       • BPREFIXFMT(x)
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112       These can be used in e.g.  the following ungainly fashion:
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114       **ncplane_printf(n, "%*s", PREFIXFMT(buf));**
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116       to ensure that the output is always PREFIXCOLUMNS wide.
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RETURN VALUES

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

123       ncmetric(0, 1, buf, 0, 1000, '\0'): "0.00".
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125       ncmetric(0, 1, buf, 1, 1000, '\0'): "0".
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127       ncmetric(1023, 1, buf, 1, 1000, '\0'): "1.02K".
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129       ncmetric(1023, 1, buf, 1, 1024, 'i'): "1023".
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131       ncmetric(1024, 1, buf, 1, 1024, 'i'): "1Ki".
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133       ncmetric(4096, 1, buf, 0, 1024, 'i'): "4.00Ki".
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135       ncmetric(0x7fffffffffffffff, 1, buf, 0, 1000, '\0'): "9.22E".
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137       ncmetric(0xffffffffffffffff, 1, buf, 0, 1000, '\0'): "18.45E".
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BUGS

140       This function is difficult to understand.
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AUTHORS

146       nick black <nickblack@linux.com>.
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150                                    v2.4.9                 notcurses_metric(3)