scanc —
use byte string as lookup table index
#include <lib/libkern/libkern.h>
int
  
  scanc(u_int
    size, const u_char
    *cp, const u_char
    table[], int
  mask);
The scanc() function scans the byte string
  cp, whose length is size. A
  character in the string is used as an index in the 256-byte
  table. If a bitwise-AND of the byte from the table and
  mask isn't zero or the string is exhausted, the scan
  stops.
The scanc() function returns the length of the rest of
  the string, including the character which made the scan stop. If the
  scanc() function exhausted the string, it returns 0.
The scanc() function emulates a VAX instruction with the
  same name.