Changeset 18dc93c in mainline

Timestamp:

2013-11-19T08:30:03Z (11 years ago)

Author:

Vojtech Horky <vojtechhorky@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

5f9768bb

Parents:

879d7745

Message:

More bit counting functions (libsoftint)

Location:

uspace/lib/softint

Files:

• generic/bits.c (modified) (1 diff)
• include/bits.h (modified) (1 diff)

uspace/lib/softint/generic/bits.c

@@ -33 +33 @@
 #include <bits.h>
 
+/** Compute number of trailing 0-bits in a number. */
+int __ctzdi2(long a)
+{
+        unsigned int bits = 0;
+        while (((a >> bits) & 1) == 0) {
+                bits++;
+                if (bits >= sizeof(a) * 8) {
+                        break;
+                }
+        }
+
+        return bits;
+}
+
+/** Compute number of trailing 0-bits in a number. */
+int __ctzsi2(int a)
+{
+        unsigned int bits = 0;
+        while (((a >> bits) & 1) == 0) {
+                bits++;
+                if (bits >= sizeof(a) * 8) {
+                        break;
+                }
+        }
+
+        return bits;
+}
+
+/** Compute number of leading 0-bits in a number. */
+int __clzdi2(long a)
+{
+        int index = sizeof(a) * 8 - 1;
+        int bits = 0;
+        while (index >= 0) {
+                if (((a >> index) & 1) == 0) {
+                        bits++;
+                } else {
+                        break;
+                }
+                index--;
+        }
+
+        return bits;
+}
+
+/** Compute index of the first 1-bit in a number increased by one.
+ *
+ * If the number is zero, zero is returned.
+ */
+int __ffsdi2(long a) {
+        if (a == 0) {
+                return 0;
+        }
+
+        return 1 + __ctzdi2(a);
+}
+
 /** Compute number of set bits in a number. */
 int __popcountsi2(int a)

uspace/lib/softint/include/bits.h

@@ -36 +36 @@
 #define __SOFTINT_BITS_H_
 
+extern int __ctzdi2(long);
+extern int __ctzsi2(int);
+extern int __clzdi2(long);
+extern int __ffsdi2(long);
 extern int __popcountsi2(int);
 extern int __popcountdi2(long);