summaryrefslogtreecommitdiffstats
path: root/contrib/qemu/util/bitops.c
diff options
context:
space:
mode:
Diffstat (limited to 'contrib/qemu/util/bitops.c')
-rw-r--r--contrib/qemu/util/bitops.c158
1 files changed, 158 insertions, 0 deletions
diff --git a/contrib/qemu/util/bitops.c b/contrib/qemu/util/bitops.c
new file mode 100644
index 00000000000..227c38b883d
--- /dev/null
+++ b/contrib/qemu/util/bitops.c
@@ -0,0 +1,158 @@
+/*
+ * 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 "qemu/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 >= 4*BITS_PER_LONG) {
+ unsigned long d1, d2, d3;
+ tmp = *p;
+ d1 = *(p+1);
+ d2 = *(p+2);
+ d3 = *(p+3);
+ if (tmp) {
+ goto found_middle;
+ }
+ if (d1 | d2 | d3) {
+ break;
+ }
+ p += 4;
+ result += 4*BITS_PER_LONG;
+ size -= 4*BITS_PER_LONG;
+ }
+ while (size >= BITS_PER_LONG) {
+ 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 + ctzl(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 + ctzl(~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 + BITS_PER_LONG - 1 - clzl(tmp);
+ }
+ }
+
+ /* Not found */
+ return size;
+}