ref: 96d6f4433550c4e48c33d94f6e272fae4b4e4ffb
dir: /sys/src/ape/lib/ap/gen/memchr.c/
#include <string.h> void* memchr(const void *ap, int c, size_t n) { unsigned char *sp; sp = ap; c &= 0xFF; while(n > 0) { if(*sp++ == c) return sp-1; n--; } return 0; }