summaryrefslogtreecommitdiffstats
path: root/lib/find_next_bit.c
diff options
context:
space:
mode:
Diffstat (limited to 'lib/find_next_bit.c')
-rw-r--r--lib/find_next_bit.c177
1 files changed, 150 insertions, 27 deletions
diff --git a/lib/find_next_bit.c b/lib/find_next_bit.c
index c05b4b1..bda0d71 100644
--- a/lib/find_next_bit.c
+++ b/lib/find_next_bit.c
@@ -11,48 +11,171 @@
#include <linux/bitops.h>
#include <linux/module.h>
+#include <asm/types.h>
+#include <asm/byteorder.h>
-int find_next_bit(const unsigned long *addr, int size, int offset)
+#define BITOP_WORD(nr) ((nr) / BITS_PER_LONG)
+
+/**
+ * find_next_bit - find the next set bit in a memory region
+ * @addr: The address to base the search on
+ * @offset: The bitnumber to start searching at
+ * @size: The maximum size to search
+ */
+unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
+ unsigned long offset)
{
- const unsigned long *base;
- const int NBITS = sizeof(*addr) * 8;
+ const unsigned long *p = addr + BITOP_WORD(offset);
+ unsigned long result = offset & ~(BITS_PER_LONG-1);
unsigned long tmp;
- base = addr;
+ if (offset >= size)
+ return size;
+ size -= result;
+ offset %= BITS_PER_LONG;
if (offset) {
- int suboffset;
+ 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;
- addr += offset / NBITS;
+found_first:
+ tmp &= (~0UL >> (BITS_PER_LONG - size));
+ if (tmp == 0UL) /* Are any bits set? */
+ return result + size; /* Nope. */
+found_middle:
+ return result + __ffs(tmp);
+}
- suboffset = offset % NBITS;
- if (suboffset) {
- tmp = *addr;
- tmp >>= suboffset;
- if (tmp)
- goto finish;
- }
+EXPORT_SYMBOL(find_next_bit);
- addr++;
+/*
+ * 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);
+}
+
+EXPORT_SYMBOL(find_next_zero_bit);
- while ((tmp = *addr) == 0)
- addr++;
+#ifdef __BIG_ENDIAN
- offset = (addr - base) * NBITS;
+/* include/linux/byteorder does not support "unsigned long" type */
+static inline unsigned long ext2_swabp(const unsigned long * x)
+{
+#if BITS_PER_LONG == 64
+ return (unsigned long) __swab64p((u64 *) x);
+#elif BITS_PER_LONG == 32
+ return (unsigned long) __swab32p((u32 *) x);
+#else
+#error BITS_PER_LONG not defined
+#endif
+}
+
+/* include/linux/byteorder doesn't support "unsigned long" type */
+static inline unsigned long ext2_swab(const unsigned long y)
+{
+#if BITS_PER_LONG == 64
+ return (unsigned long) __swab64((u64) y);
+#elif BITS_PER_LONG == 32
+ return (unsigned long) __swab32((u32) y);
+#else
+#error BITS_PER_LONG not defined
+#endif
+}
- finish:
- /* count the remaining bits without using __ffs() since that takes a 32-bit arg */
- while (!(tmp & 0xff)) {
- offset += 8;
- tmp >>= 8;
+unsigned long generic_find_next_zero_le_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 - 1UL);
+ if (offset) {
+ tmp = ext2_swabp(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 (!(tmp & 1)) {
- offset++;
- tmp >>= 1;
+ while (size & ~(BITS_PER_LONG - 1)) {
+ if (~(tmp = *(p++)))
+ goto found_middle_swap;
+ result += BITS_PER_LONG;
+ size -= BITS_PER_LONG;
}
+ if (!size)
+ return result;
+ tmp = ext2_swabp(p);
+found_first:
+ tmp |= ~0UL << size;
+ if (tmp == ~0UL) /* Are any bits zero? */
+ return result + size; /* Nope. Skip ffz */
+found_middle:
+ return result + ffz(tmp);
- return offset;
+found_middle_swap:
+ return result + ffz(ext2_swab(tmp));
}
-EXPORT_SYMBOL(find_next_bit);
+EXPORT_SYMBOL(generic_find_next_zero_le_bit);
+
+#endif /* __BIG_ENDIAN */
OpenPOWER on IntegriCloud