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authorAndrew Bartlett <abartlet@samba.org>2011-06-24 16:26:23 +1000
committerAndrew Bartlett <abartlet@samba.org>2011-06-24 16:26:23 +1000
commit6da26870e0ae5acd6ff49a30ec2f6886b44d095e (patch)
tree850c71039563c16a5d563c47e7ba2ab645baf198 /lib/ccan/ilog/_info
parent6925a799d04c6fa59dd2ddef1f5510f9bb7d17d1 (diff)
parent2610c05b5b95cc7036b3d6dfb894c6cfbdb68483 (diff)
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Merge 2610c05b5b95cc7036b3d6dfb894c6cfbdb68483 as Samba-4.0alpha16
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+/**
+ * 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 <stdio.h>
+ * #include <limits.h>
+ * #include <ccan/ilog/ilog.h>
+ *
+ * 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 <tterribe@xiph.org>
+ */
+#include <string.h>
+#include <stdio.h>
+#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;
+}