.\"	$NetBSD: humanize_number.3,v 1.5 2005/04/11 12:19:16 wiz Exp $
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.Dd September 14, 2008
.Dt HUMANIZE_NUMBER 3
.Os
.Sh NAME
.Nm dehumanize_number ,
.Nm humanize_number
.Nd format a number into a human readable form and vice versa
.Sh LIBRARY
.Lb libutil
.Sh SYNOPSIS
.In sys/types.h
.In libutil.h
.Ft int
.Fn dehumanize_number "const char *str" "int64_t *result"
.Ft int
.Fo humanize_number
.Fa "char *buf" "size_t len" "int64_t number" "const char *suffix"
.Fa "int scale" "int flags"
.Fc
.Sh DESCRIPTION
The
.Fn humanize_number
function formats the signed 64 bit quantity given in
.Fa number
into
.Fa buffer .
A space and then
.Fa suffix
is appended to the end.
The buffer pointed to by
.Fa buffer
must be at least
.Fa len
bytes long.
.Pp
If the formatted number (including
.Fa suffix )
would be too long to fit into
.Fa buffer ,
then divide
.Fa number
by 1024 until it will.
In this case, prefix
.Fa suffix
with the appropriate SI designator.
The
.Fn humanize_number
function
follows the traditional computer science conventions rather than the proposed
SI power of two convention.
.Pp
The prefixes are:
.Bl -column "Prefix" "Description" "1000000000000000000" -offset indent
.It Sy "Prefix" Ta Sy "Description" Ta Sy "Multiplier" Ta Sy "Multiplier 1000x"
.It Li k Ta No kilo Ta 1024 Ta 1000
.It Li M Ta No mega Ta 1048576 Ta 1000000
.It Li G Ta No giga Ta 1073741824 Ta 1000000000
.It Li T Ta No tera Ta 1099511627776 Ta 1000000000000
.It Li P Ta No peta Ta 1125899906842624 Ta 1000000000000000
.It Li E Ta No exa Ta 1152921504606846976 Ta 1000000000000000000
.El
.Pp
The
.Fa len
argument must be at least 4 plus the length of
.Fa suffix ,
in order to ensure a useful result is generated into
.Fa buffer .
To use a specific prefix, specify this as
.Fa scale
(multiplier = 1024 ^ scale).
This cannot be combined with any of the
.Fa scale
flags below.
.Pp
The following flags may be passed in
.Fa scale :
.Bl -tag -width ".Dv HN_DIVISOR_1000" -offset indent
.It Dv HN_AUTOSCALE
Format the buffer using the lowest multiplier possible.
.It Dv HN_GETSCALE
Return the prefix index number (the number of times
.Fa number
must be divided to fit) instead of formatting it to the buffer.
.El
.Pp
The following flags may be passed in
.Fa flags :
.Bl -tag -width ".Dv HN_DIVISOR_1000" -offset indent
.It Dv HN_DECIMAL
If the final result is less than 10, display it using one digit.
.It Dv HN_NOSPACE
Do not put a space between
.Fa number
and the prefix.
.It Dv HN_B
Use
.Ql B
(bytes) as prefix if the original result does not have a prefix.
.It Dv HN_DIVISOR_1000
Divide
.Fa number
with 1000 instead of 1024.
.El
.Pp
The
.Fn dehumanize_number
function parses the string representing an integral value given in
.Fa str
and stores the numerical value in the integer pointed to by
.Fa result .
The provided string may hold one of the suffixes, which will be interpreted
and used to scale up its accompanying numerical value.
.Sh RETURN VALUES
The
.Fn humanize_number
function returns the number of characters stored in
.Fa buffer
(excluding the terminating
.Dv NUL )
upon success, or \-1 upon failure.
If
.Dv HN_GETSCALE
is specified, the prefix index number will be returned instead.
.Pp
The
.Fn dehumanize_number
function returns 0 if the string was parsed correctly.
A \-1 is returned to indicate failure and an error code is stored in
.Va errno .
.Sh ERRORS
The
.Fn dehumanize_number
function will fail and no number will be stored in
.Fa result
if:
.Bl -tag -width Er
.It Bq Er EINVAL
The string in
.Fa str
was empty or carried an unknown suffix.
.It Bq Er ERANGE
The string in
.Fa str
represented a number that does not fit in
.Fa result .
.El
.Sh HISTORY
The
.Fn humanize_number
function first appeared in
.Nx 2.0
and then in
.Fx 5.3 .
.Pp
The
.Fn dehumanize_number
function first appeared in
.Nx 5.0 .