/** * ilog - Integer logarithm. * * ilog_32() and ilog_64() compute the minimum number of bits required to store * an unsigned 32-bit or 64-bit value without any leading zero bits. * This can also be thought of as the location of the highest set bit, with * counting starting from one (so that 0 returns 0, 1 returns 1, and 2**31 * returns 32). * When the value is known to be non-zero ilog32_nz() and ilog64_nz() can * compile into as few as two instructions, one of which may get optimized out * later. * STATIC_ILOG_32 and STATIC_ILOG_64 allow computation on compile-time * constants, so other compile-time constants can be derived from them. * * Example: * #include * #include * #include * * int main(void){ * int i; * printf("ilog32(0x%08X)=%i\n",0,ilog32(0)); * for(i=1;i<=STATIC_ILOG_32(USHRT_MAX);i++){ * uint32_t v; * v=(uint32_t)1U<<(i-1); * //Here we know v is non-zero, so we can use ilog32_nz(). * printf("ilog32(0x%08X)=%i\n",v,ilog32_nz(v)); * } * return 0; * } * * License: LGPL (v2 or later) * Author: Timothy B. Terriberry */ #include #include #include "config.h" int main(int _argc,const char *_argv[]){ /*Expect exactly one argument.*/ if(_argc!=2)return 1; if(strcmp(_argv[1],"depends")==0){ printf("ccan/compiler\n"); return 0; } return 1; }