1 files changed, 153 insertions, 0 deletions
diff --git a/src/util/bitscan.h b/src/util/bitscan.h
new file mode 100644
index 00000000000..4999b744d1d
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+++ b/src/util/bitscan.h
@@ -0,0 +1,153 @@
+/**************************************************************************
+ *
+ * Copyright 2008 VMware, Inc.
+ * All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sub license, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
+ * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
+ * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ **************************************************************************/
+
+
+#ifndef BITSCAN_H
+#define BITSCAN_H
+
+#include <stdint.h>
+
+#if defined(_MSC_VER)
+#include <intrin.h>
+#endif
+
+#include "c99_compat.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+/**
+ * Find first bit set in word.  Least significant bit is 1.
+ * Return 0 if no bits set.
+ */
+#ifdef HAVE___BUILTIN_FFS
+#define ffs __builtin_ffs
+#elif defined(_MSC_VER) && (_M_IX86 || _M_ARM || _M_AMD64 || _M_IA64)
+static inline
+int ffs(unsigned i)
+{
+   unsigned long index;
+   if (_BitScanForward(&index, i))
+      return index + 1;
+   else
+      return 0;
+}
+#else
+extern
+int ffs(unsigned i);
+#endif
+
+#ifdef HAVE___BUILTIN_FFSLL
+#define ffsll __builtin_ffsll
+#elif defined(_MSC_VER) && (_M_AMD64 || _M_ARM || _M_IA64)
+static inline int
+ffsll(uint64_t i)
+{
+   unsigned long index;
+   if (_BitScanForward64(&index, i))
+      return index + 1;
+   else
+      return 0;
+}
+#else
+extern int
+ffsll(uint64_t val);
+#endif
+
+
+/* Destructively loop over all of the bits in a mask as in:
+ *
+ * while (mymask) {
+ *   int i = u_bit_scan(&mymask);
+ *   ... process element i
+ * }
+ *
+ */
+static inline int
+u_bit_scan(unsigned *mask)
+{
+   const int i = ffs(*mask) - 1;
+   *mask ^= (1u << i);
+   return i;
+}
+
+static inline int
+u_bit_scan64(uint64_t *mask)
+{
+   const int i = ffsll(*mask) - 1;
+   *mask ^= (((uint64_t)1) << i);
+   return i;
+}
+
+/* For looping over a bitmask when you want to loop over consecutive bits
+ * manually, for example:
+ *
+ * while (mask) {
+ *    int start, count, i;
+ *
+ *    u_bit_scan_consecutive_range(&mask, &start, &count);
+ *
+ *    for (i = 0; i < count; i++)
+ *       ... process element (start+i)
+ * }
+ */
+static inline void
+u_bit_scan_consecutive_range(unsigned *mask, int *start, int *count)
+{
+   if (*mask == 0xffffffff) {
+      *start = 0;
+      *count = 32;
+      *mask = 0;
+      return;
+   }
+   *start = ffs(*mask) - 1;
+   *count = ffs(~(*mask >> *start)) - 1;
+   *mask &= ~(((1u << *count) - 1) << *start);
+}
+
+static inline void
+u_bit_scan_consecutive_range64(uint64_t *mask, int *start, int *count)
+{
+   if (*mask == ~0llu) {
+      *start = 0;
+      *count = 64;
+      *mask = 0;
+      return;
+   }
+   *start = ffsll(*mask) - 1;
+   *count = ffsll(~(*mask >> *start)) - 1;
+   *mask &= ~(((((uint64_t)1) << *count) - 1) << *start);
+}
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* BITSCAN_H */