bitmask_snprintf(9) - NetBSD Manual Pages

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BITMASK_SNPRINTF(9)    NetBSD Kernel Developer's Manual    BITMASK_SNPRINTF(9)


NAME

     bitmask_snprintf - bitmask output conversion


SYNOPSIS

     #include <sys/systm.h>

     void
     bitmask_snprintf(u_quad_t val, const char *fmt, char *buf,
             size_t buflen);


DESCRIPTION

     The bitmask_snprintf() function formats a bitmask into a mnemonic form
     suitable for printing.

     This conversion is useful for decoding bit fields in device registers.
     It formats the integer val into the buffer buf, of size buflen, using a
     specified radix and an interpretation of the bits within that integer as
     though they were flags.

     The decoding directive string fmt describes how the bitfield is to be
     interpreted and displayed.  The first character of fmt is a binary char-
     acter representation of the output numeral base in which the bitfield
     will be printed before it is decoded.  Recognized radix values (in C
     escape-character format) are \10 (octal), \12 (decimal), and \20
     (hexadecimal).

     The remaining characters in fmt are interpreted as a list of bit-posi-
     tion-description pairs.  A bit-position-description 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 (octal 40, hexadecimal 20, the ASCII
     space character) describes the most significant bit.

     The remaining characters in a bit-position-description pair are the char-
     acters to print should the bit being described be set.  Description
     strings are delimited by the next bit position value character encoun-
     tered (distinguishable by its value being <= 32), or the end of the
     decoding directive string itself.


RETURN VALUES

     The bitmask_snprintf() function returns the buffer buf.  The returned
     string is always NULL-terminated.


EXAMPLES

     Two examples of the old formatting style:

           bitmask_snprintf(3, "\10\2BITTWO\1BITONE", buf, buflen)
           => "3<BITTWO,BITONE>"

           bitmask_snprintf(0xe860,
                  "\20\x10NOTBOOT\x0fFPP\x0eSDVMA\x0cVIDEO"
                  "\x0bLORES\x0aFPA\x09DIAG\x07CACHE"
                  "\x06IOCACHE\x05LOOPBACK\x04DBGCACHE",
                   buf, buflen)
           => "e860<NOTBOOT,FPP,SDVMA,VIDEO,CACHE,IOCACHE>"


ERRORS

     If the buffer buf is too small to hold the formatted output,
     bitmask_snprintf() will still return the buffer, containing a truncated
     string.


SEE ALSO

     printf(9)


CODE REFERENCES

     sys/kern/subr_prf.c


HISTORY

     The bitmask_snprintf() function was originally implemented as a non-stan-
     dard %b format string for the kernel printf() function in NetBSD 1.5 and
     earlier releases.


BUGS

     bitmask_snprintf() supports a new extended form of formatting string,
     which is not yet described here.

NetBSD 2.0.2                     July 28, 2000                    NetBSD 2.0.2