151 lines
4.9 KiB
Groff
151 lines
4.9 KiB
Groff
.\" $NetBSD: snprintb.3,v 1.5 2004/12/01 00:06:46 peter Exp $
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.\"
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.\" Copyright (c) 1998 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Jeremy Cooper.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd July 28, 2000
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.Dt SNPRINTB 3
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.Os
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.Sh NAME
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.Nm snprintb
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.Nd bitmask output conversion
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.Sh LIBRARY
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.Lb libutil
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.Sh SYNOPSIS
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.In util.h
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.Ft int
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.Fn "snprintb" "char *buf" "size_t buflen" "const char *fmt" "uint64_t val"
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.Sh DESCRIPTION
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The
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.Fn snprintb
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function formats a bitmask into a mnemonic form suitable for printing.
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.Pp
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This conversion is useful for decoding bit fields in device registers.
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It formats the integer
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.Fa val
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into the buffer
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.Fa buf ,
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of size
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.Fa buflen ,
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using a specified radix and an interpretation of
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the bits within that integer as though they were flags.
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.Pp
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The decoding directive string
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.Fa fmt
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describes how the bitfield is to be interpreted and displayed.
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The first character of
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.Fa fmt
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is a binary character representation of the
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output numeral base in which the bitfield will be printed before it is decoded.
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Recognized radix values
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.Pq "in C escape-character format"
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are
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.Li \e10
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.Pq octal ,
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.Li \e12
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.Pq decimal ,
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and
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.Li \e20
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.Pq hexadecimal .
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.Pp
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The remaining characters in
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.Fa fmt
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are interpreted as a list of bit-position\(endescription pairs.
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A bit-position\(endescription pair begins with a binary character value
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that represents the position of the bit being described.
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A bit position value of one describes the least significant bit.
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Whereas a position value of 32
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.Pq "octal 40, hexadecimal 20, the ASCII space character"
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describes the most significant bit.
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.Pp
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The remaining characters in a bit-position\(endescription pair are the
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characters to print should the bit being described be set.
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Description strings are delimited by the next bit position value character
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encountered
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.Pq "distinguishable by its value being \*[Le] 32" ,
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or the end of the decoding directive string itself.
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.Sh RETURN VALUES
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The
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.Fn snprintb
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function returns the number of characters that are required to format the
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value
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.Fa val
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given the format string
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.Fa fmt
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excluding the terminating NUL.
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The returned string in
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.Fa buf
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is always NUL-terminated.
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.Sh EXAMPLES
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Two examples of the old formatting style:
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.Bd -literal -offset indent
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snprintb(buf, buflen, "\e10\e2BITTWO\e1BITONE", 3)
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\(rA "3\*[Lt]BITTWO,BITONE\*[Gt]"
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snprintb(buf, buflen
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"\e20\ex10NOTBOOT\ex0fFPP\ex0eSDVMA\ex0cVIDEO"
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"\ex0bLORES\ex0aFPA\ex09DIAG\ex07CACHE"
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"\ex06IOCACHE\ex05LOOPBACK\ex04DBGCACHE",
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0xe860)
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\(rA "0xe860\*[Lt]NOTBOOT,FPP,SDVMA,VIDEO,CACHE,IOCACHE\*[Gt]"
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.Ed
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.Sh ERRORS
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If the buffer
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.Fa buf
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is too small to hold the formatted output,
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.Fn snprintb
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will still return the buffer, containing a truncated string.
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.Sh SEE ALSO
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.Xr snprintf 3
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.Sh HISTORY
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The
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.Fn snprintb
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function was originally implemented as a non-standard
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.Li %b
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format string for the kernel
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.Fn printf
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function in
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.Nx 1.5
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and earlier releases.
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It got implemented as
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.Fn bitmap_snprintf
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for
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.Nx 1.6
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and this version was used to implement
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.Fn snprintb .
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.Sh BUGS
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.Fn snprintb
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supports a new extended form of formatting string, which is not yet
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described here.
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