1 files changed, 142 insertions, 0 deletions
diff --git a/bitops.c b/bitops.c
new file mode 100644
index 0000000000..d9de71f7e8
--- /dev/null
+++ b/bitops.c
@@ -0,0 +1,142 @@
+/*
+ * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ * Copyright (C) 2008 IBM Corporation
+ * Written by Rusty Russell <rusty@rustcorp.com.au>
+ * (Inspired by David Howell's find_next_bit implementation)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include "bitops.h"
+
+#define BITOP_WORD(nr)		((nr) / BITS_PER_LONG)
+
+/*
+ * Find the next set bit in a memory region.
+ */
+unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
+			    unsigned long offset)
+{
+    const unsigned long *p = addr + BITOP_WORD(offset);
+    unsigned long result = offset & ~(BITS_PER_LONG-1);
+    unsigned long tmp;
+
+    if (offset >= size) {
+        return size;
+    }
+    size -= result;
+    offset %= BITS_PER_LONG;
+    if (offset) {
+        tmp = *(p++);
+        tmp &= (~0UL << offset);
+        if (size < BITS_PER_LONG) {
+            goto found_first;
+        }
+        if (tmp) {
+            goto found_middle;
+        }
+        size -= BITS_PER_LONG;
+        result += BITS_PER_LONG;
+    }
+    while (size & ~(BITS_PER_LONG-1)) {
+        if ((tmp = *(p++))) {
+            goto found_middle;
+        }
+        result += BITS_PER_LONG;
+        size -= BITS_PER_LONG;
+    }
+    if (!size) {
+        return result;
+    }
+    tmp = *p;
+
+found_first:
+    tmp &= (~0UL >> (BITS_PER_LONG - size));
+    if (tmp == 0UL) {		/* Are any bits set? */
+        return result + size;	/* Nope. */
+    }
+found_middle:
+    return result + bitops_ffsl(tmp);
+}
+
+/*
+ * This implementation of find_{first,next}_zero_bit was stolen from
+ * Linus' asm-alpha/bitops.h.
+ */
+unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
+				 unsigned long offset)
+{
+    const unsigned long *p = addr + BITOP_WORD(offset);
+    unsigned long result = offset & ~(BITS_PER_LONG-1);
+    unsigned long tmp;
+
+    if (offset >= size) {
+        return size;
+    }
+    size -= result;
+    offset %= BITS_PER_LONG;
+    if (offset) {
+        tmp = *(p++);
+        tmp |= ~0UL >> (BITS_PER_LONG - offset);
+        if (size < BITS_PER_LONG) {
+            goto found_first;
+        }
+        if (~tmp) {
+            goto found_middle;
+        }
+        size -= BITS_PER_LONG;
+        result += BITS_PER_LONG;
+    }
+    while (size & ~(BITS_PER_LONG-1)) {
+        if (~(tmp = *(p++))) {
+            goto found_middle;
+        }
+        result += BITS_PER_LONG;
+        size -= BITS_PER_LONG;
+    }
+    if (!size) {
+        return result;
+    }
+    tmp = *p;
+
+found_first:
+    tmp |= ~0UL << size;
+    if (tmp == ~0UL) {	/* Are any bits zero? */
+        return result + size;	/* Nope. */
+    }
+found_middle:
+    return result + ffz(tmp);
+}
+
+unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
+{
+    unsigned long words;
+    unsigned long tmp;
+
+    /* Start at final word. */
+    words = size / BITS_PER_LONG;
+
+    /* Partial final word? */
+    if (size & (BITS_PER_LONG-1)) {
+        tmp = (addr[words] & (~0UL >> (BITS_PER_LONG
+                                       - (size & (BITS_PER_LONG-1)))));
+        if (tmp) {
+            goto found;
+        }
+    }
+
+    while (words) {
+        tmp = addr[--words];
+        if (tmp) {
+        found:
+            return words * BITS_PER_LONG + bitops_flsl(tmp);
+        }
+    }
+
+    /* Not found */
+    return size;
+}