Basically just a trivial adaption of the find_first_zero() function
for bitarray-based bitmaps.
Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
---
lib/ext2fs/blkmap64_ba.c | 77 +++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 76 insertions(+), 1 deletion(-)
diff --git a/lib/ext2fs/blkmap64_ba.c b/lib/ext2fs/blkmap64_ba.c
index 284236d..894293a 100644
--- a/lib/ext2fs/blkmap64_ba.c
+++ b/lib/ext2fs/blkmap64_ba.c
@@ -391,6 +391,80 @@ static errcode_t ba_find_first_zero(ext2fs_generic_bitmap bitmap,
return ENOENT;
}
+/* Find the first one bit between start and end, inclusive. */
+static errcode_t ba_find_first_set(ext2fs_generic_bitmap bitmap,
+ __u64 start, __u64 end, __u64 *out)
+{
+ ext2fs_ba_private bp = (ext2fs_ba_private)bitmap->private;
+ unsigned long bitpos = start - bitmap->start;
+ unsigned long count = end - start + 1;
+ int byte_found = 0; /* whether a != 0xff byte has been found */
+ const unsigned char *pos;
+ unsigned long max_loop_count, i;
+
+ /* scan bits until we hit a byte boundary */
+ while ((bitpos & 0x7) != 0 && count > 0) {
+ if (ext2fs_test_bit64(bitpos, bp->bitarray)) {
+ *out = bitpos + bitmap->start;
+ return 0;
+ }
+ bitpos++;
+ count--;
+ }
+
+ if (!count)
+ return ENOENT;
+
+ pos = ((unsigned char *)bp->bitarray) + (bitpos >> 3);
+ /* scan bytes until 8-byte (64-bit) aligned */
+ while (count >= 8 && (((unsigned long)pos) & 0x07)) {
+ if (*pos != 0) {
+ byte_found = 1;
+ break;
+ }
+ pos++;
+ count -= 8;
+ bitpos += 8;
+ }
+
+ if (!byte_found) {
+ max_loop_count = count >> 6; /* 8-byte blocks */
+ i = max_loop_count;
+ while (i) {
+ if (*((const __u64 *)pos) != 0)
+ break;
+ pos += 8;
+ i--;
+ }
+ count -= 64 * (max_loop_count - i);
+ bitpos += 64 * (max_loop_count - i);
+
+ max_loop_count = count >> 3;
+ i = max_loop_count;
+ while (i) {
+ if (*pos != 0) {
+ byte_found = 1;
+ break;
+ }
+ pos++;
+ i--;
+ }
+ count -= 8 * (max_loop_count - i);
+ bitpos += 8 * (max_loop_count - i);
+ }
+
+ /* Here either count < 8 or byte_found == 1. */
+ while (count-- > 0) {
+ if (ext2fs_test_bit64(bitpos, bp->bitarray)) {
+ *out = bitpos + bitmap->start;
+ return 0;
+ }
+ bitpos++;
+ }
+
+ return ENOENT;
+}
+
struct ext2_bitmap_ops ext2fs_blkmap64_bitarray = {
.type = EXT2FS_BMAP64_BITARRAY,
.new_bmap = ba_new_bmap,
@@ -407,5 +481,6 @@ struct ext2_bitmap_ops ext2fs_blkmap64_bitarray = {
.get_bmap_range = ba_get_bmap_range,
.clear_bmap = ba_clear_bmap,
.print_stats = ba_print_stats,
- .find_first_zero = ba_find_first_zero
+ .find_first_zero = ba_find_first_zero,
+ .find_first_set = ba_find_first_set
};
--
1.8.5.rc3.362.gdf10213
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