2 * ilog - Integer logarithm.
4 * ilog_32() and ilog_64() compute the minimum number of bits required to store
5 * an unsigned 32-bit or 64-bit value without any leading zero bits.
7 * This can also be thought of as the location of the highest set bit, with
8 * counting starting from one (so that 0 returns 0, 1 returns 1, and 2**31
11 * When the value is known to be non-zero ilog32_nz() and ilog64_nz() can
12 * compile into as few as two instructions, one of which may get optimized out
15 * STATIC_ILOG_32 and STATIC_ILOG_64 allow computation on compile-time
16 * constants, so other compile-time constants can be derived from them.
21 * #include <ccan/ilog/ilog.h>
25 * printf("ilog32(0x%08X)=%i\n",0,ilog32(0));
26 * for(i=1;i<=STATIC_ILOG_32(USHRT_MAX);i++){
28 * v=(uint32_t)1U<<(i-1);
29 * //Here we know v is non-zero, so we can use ilog32_nz().
30 * printf("ilog32(0x%08X)=%i\n",v,ilog32_nz(v));
35 * License: CC0 (Public domain)
36 * Author: Timothy B. Terriberry <tterribe@xiph.org>
42 int main(int _argc,const char *_argv[]){
43 /*Expect exactly one argument.*/
45 if(strcmp(_argv[1],"depends")==0){
46 printf("ccan/compiler\n");