int
snprintb(
char *buf
, size_t buflen
, const char *fmt
, uint64_t val
)
)
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 character 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-position-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 characters to print should the bit being described be set. Description strings are delimited by the next bit position value character encountered (distinguishable by its value being 32), or the end of the decoding directive string itself.
)
function returns the number of characters that are required to format the
value
val
given the format string
fmt
excluding the terminating NUL.
The returned string in
buf
is always NUL-terminated.
snprintb(buf, buflen, "\10\2BITTWO\1BITONE", 3)
=> "3<BITTWO,BITONE>"
snprintb(buf, buflen
"\20\x10NOTBOOT\x0fFPP\x0eSDVMA\x0cVIDEO"
"\x0bLORES\x0aFPA\x09DIAG\x07CACHE"
"\x06IOCACHE\x05LOOPBACK\x04DBGCACHE",
0xe860)
=> "0xe860<NOTBOOT,FPP,SDVMA,VIDEO,CACHE,IOCACHE>"
buf
is too small to hold the formatted output,
snprintb(
)
will still return the buffer, containing a truncated string.
)
function was originally implemented as a non-standard
%b
format string for the kernel
printf(
)
function in
NetBSD1.5
and earlier releases.
It got implemented as
bitmap_snprintf(
)
for
NetBSD1.6
and this version was used to implement
snprintb(
).
)
supports a new extended form of formatting string, which is not yet
described here.