NetBSD/share/man/man9/bitmask_snprintf.9

.\"     $NetBSD: bitmask_snprintf.9,v 1.1 2000/08/09 03:12:33 tv Exp $
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.Dd July 28, 2000
.Dt BITMASK_SNPRINTF 9
.Os
.Sh NAME
.Nm bitmask_snprintf
.Nd bitmask output conversion
.Sh SYNOPSIS
.Fd #include <sys/systm.h>
.Ft void
.Fn "bitmask_snprintf" "u_quad_t val" "const char *fmt" "char *buf" "size_t buflen"
.Sh DESCRIPTION
The
.Fn bitmask_snprintf
function formats a bitmask into a mnemonic form suitable for printing.
.Pp
This conversion is useful for decoding bit fields in device registers.
It formats the integer
.Fa val
into the buffer
.Fa buf ,
of size
.Fa buflen ,
using a specified radix and an interpretation of
the bits within that integer as though they were flags.
.Pp
The decoding directive string
.Fa fmt
describes how the bitfield is to be interpreted and displayed.
The first character of
.Fa fmt
is a binary character representation of the
output numeral base in which the bitfield will be printed before it is decoded.
Recognized radix values
.Pq "in C escape-character format"
are
.Li \e10
.Pq octal ,
.Li \e12
.Pq decimal ,
and
.Li \e20
.Pq hexadecimal .
.Pp
The remaining characters in
.Fa fmt
are interpreted as a list of bit-position\(endescription pairs.
A bit-position\(endescription pair begins with a binary character value
that represents the position of the bit being described.
A bit position value of one describes the least significant bit.
Whereas a position value of 32
.Pq "octal 40, hexadecimal 20, the ASCII space character"
describes the most significant bit.
.Pp
The remaining characters in a bit-position\(endescription pair are the
characters to print should the bit being described be set.
Description strings are delimited by the next bit position value character
encountered
.Pq "distinguishable by its value being \(<= 32" ,
or the end of the decoding directive string itself.
.Sh RETURN VALUES
The
.Fn bitmask_snprintf
function returns the buffer
.Fa buf .
The returned string is always NULL-terminated.
.Sh EXAMPLES
Two examples of the old formatting style:
.Bd -literal -offset indent
bitmask_snprintf(3, "\e10\e2BITTWO\e1BITONE", buf, buflen)
\(rA "3<BITTWO,BITONE>"

bitmask_snprintf(0xe860,
       "\e20\ex10NOTBOOT\ex0fFPP\ex0eSDVMA\ex0cVIDEO"
       "\ex0bLORES\ex0aFPA\ex09DIAG\ex07CACHE"
       "\ex06IOCACHE\ex05LOOPBACK\ex04DBGCACHE",
        buf, buflen)
\(rA "e860<NOTBOOT,FPP,SDVMA,VIDEO,CACHE,IOCACHE>"
.Ed
.Sh ERRORS
If the buffer
.Fa buf
is too small to hold the formatted output,
.Fn bitmask_snprintf
will still return the buffer, containing a truncated string.
.Sh SEE ALSO
.Xr printf 9
.Sh CODE REFERENCES
.Pa sys/kern/subr_prf.c
.Sh HISTORY
The
.Fn bitmask_snprintf
function was originally implemented as a non-standard
.Li %b
format string for the kernel
.Fn printf 
function in
.Nx 1.5
and earlier releases.
.Sh BUGS
.Fn bitmask_snprintf
supports a new extended form of formatting string, which is not yet
described here.