July 28, 2000 SNPRINTB 3

### NAME

snprintb - bitmask output conversion

### LIBRARY

System Utilities Library (libutil, -lutil)

### SYNOPSIS

```int` snprintb(```char *buf``, size_t buflen``, const char *fmt``, uint64_t val`)

### DESCRIPTION

The snprintb(``) 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.

### RETURN VALUES

The snprintb(``) 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.

### EXAMPLES

Two examples of the old formatting style:

  `

      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>"

  `

### ERRORS

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

### SEE ALSO

snprintf(3)

### HISTORY

The snprintb(``) 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(``).

### BUGS

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