This is xnu-6153.11.26. See this file in:
Directory listing for xnu-6153.11.26//bsd/libkern
Makefile
bcd.c
copyio.h
crc16.c
crc32.c
libkern.h
memchr.c
random.c
scanc.c
skpc.c
strsep.c
url_encode.c