This function efficiently counts the number of bits in a block of
memory.
Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
Reviewed-by: Lukas Czerner <lczerner@xxxxxxxxxx>
---
Renamed function signature to make it clear that ext2fs_bitcount takes
the number of bytes, not number of bits.
Enhance the unit test to make sure the popcount function is more
thoroughly tested.
lib/ext2fs/bitops.c | 35 ++++++++++++++++
lib/ext2fs/bitops.h | 1 +
lib/ext2fs/tst_bitmaps.c | 1 +
lib/ext2fs/tst_bitmaps_cmds | 42 ++++++++++++++++++++
lib/ext2fs/tst_bitmaps_exp | 97 +++++++++++++++++++++++++++++++++++++++++++++
5 files changed, 176 insertions(+)
diff --git a/lib/ext2fs/bitops.c b/lib/ext2fs/bitops.c
index 9322a35..7f5b66f 100644
--- a/lib/ext2fs/bitops.c
+++ b/lib/ext2fs/bitops.c
@@ -116,3 +116,38 @@ int ext2fs_test_bit64(__u64 nr, const void * addr)
return (mask & *ADDR);
}
+static unsigned int popcount8(unsigned int w)
+{
+ unsigned int res = w - ((w >> 1) & 0x55);
+ res = (res & 0x33) + ((res >> 2) & 0x33);
+ return (res + (res >> 4)) & 0x0F;
+}
+
+static unsigned int popcount32(unsigned int w)
+{
+ unsigned int res = w - ((w >> 1) & 0x55555555);
+ res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
+ res = (res + (res >> 4)) & 0x0F0F0F0F;
+ res = res + (res >> 8);
+ return (res + (res >> 16)) & 0x000000FF;
+}
+
+unsigned int ext2fs_bitcount(const void *addr, unsigned int count)
+{
+ const unsigned char *cp = addr;
+ const __u32 *p = addr;
+ unsigned int res = 0;
+
+ if ((((unsigned long) addr) & 3) == 0) {
+ while (count > 4) {
+ res += popcount32(*p++);
+ count -= 4;
+ }
+ cp = (const unsigned char *) p;
+ }
+ while (count > 0) {
+ res += popcount8(*cp++);
+ count--;
+ }
+ return res;
+}
diff --git a/lib/ext2fs/bitops.h b/lib/ext2fs/bitops.h
index 526870f..17e707c 100644
--- a/lib/ext2fs/bitops.h
+++ b/lib/ext2fs/bitops.h
@@ -686,6 +686,7 @@ extern int ext2fs_test_bit(unsigned int nr, const void * addr);
extern int ext2fs_set_bit64(__u64 nr,void * addr);
extern int ext2fs_clear_bit64(__u64 nr, void * addr);
extern int ext2fs_test_bit64(__u64 nr, const void * addr);
+extern unsigned int ext2fs_bitcount(const void *addr, unsigned int count);
#ifdef NO_INLINE_FUNCS
extern void ext2fs_fast_set_bit(unsigned int nr,void * addr);
diff --git a/lib/ext2fs/tst_bitmaps.c b/lib/ext2fs/tst_bitmaps.c
index 5da3693..2a76292 100644
--- a/lib/ext2fs/tst_bitmaps.c
+++ b/lib/ext2fs/tst_bitmaps.c
@@ -270,6 +270,7 @@ void dump_bitmap(ext2fs_generic_bitmap bmap, unsigned int start, unsigned num)
for (i=0; i < len; i++)
printf("%02x", buf[i]);
printf("\n");
+ printf("bits set: %u\n", ext2fs_bitcount(buf, len));
free(buf);
}
diff --git a/lib/ext2fs/tst_bitmaps_cmds b/lib/ext2fs/tst_bitmaps_cmds
index 9a4f3d0..31e2a60 100644
--- a/lib/ext2fs/tst_bitmaps_cmds
+++ b/lib/ext2fs/tst_bitmaps_cmds
@@ -53,5 +53,47 @@ cleari 5
testi 17
testi 6
testi 4
+clearb 7 12
+dump_bb
+setb 1
+dump_bb
+setb 2
+dump_bb
+setb 3
+dump_bb
+setb 4
+dump_bb
+setb 5
+dump_bb
+setb 6
+dump_bb
+setb 7
+dump_bb
+setb 8
+dump_bb
+setb 10
+setb 12
+setb 14
+setb 17
+setb 19
+setb 24
+setb 26
+setb 27
+setb 30
+setb 31
+setb 32
+setb 35
+setb 39
+setb 40
+setb 44
+setb 46
+setb 47
+setb 49
+setb 51
+setb 52
+clearb 2
+clearb 3
+clearb 7
+dump_bb
quit
diff --git a/lib/ext2fs/tst_bitmaps_exp b/lib/ext2fs/tst_bitmaps_exp
index 2d406ce..2d62b66 100644
--- a/lib/ext2fs/tst_bitmaps_exp
+++ b/lib/ext2fs/tst_bitmaps_exp
@@ -36,6 +36,7 @@ tst_bitmaps: testb 16
Block 16 is set
tst_bitmaps: dump_bb
block bitmap: 00f80000000000000000000000000000
+bits set: 5
tst_bitmaps: ffzb 11 16
First unmarked block is 11
tst_bitmaps: ffzb 12 16
@@ -64,6 +65,7 @@ tst_bitmaps: setb 12 7
Marking blocks 12 to 18
tst_bitmaps: dump_bb
block bitmap: 00f80300000000000000000000000000
+bits set: 7
tst_bitmaps: seti 2
Setting inode 2, was clear before
tst_bitmaps: seti 5
@@ -82,6 +84,7 @@ tst_bitmaps: testi 1
Inode 1 is clear
tst_bitmaps: dump_ib
inode bitmap: 1e000000
+bits set: 4
tst_bitmaps: ffzi 1 6
First unmarked inode is 1
tst_bitmaps: ffzi 2 5
@@ -110,5 +113,99 @@ tst_bitmaps: testi 6
Inode 6 is clear
tst_bitmaps: testi 4
Inode 4 is clear
+tst_bitmaps: clearb 7 12
+Clearing blocks 7 to 18
+tst_bitmaps: dump_bb
+block bitmap: 00000000000000000000000000000000
+bits set: 0
+tst_bitmaps: setb 1
+Setting block 1, was clear before
+tst_bitmaps: dump_bb
+block bitmap: 01000000000000000000000000000000
+bits set: 1
+tst_bitmaps: setb 2
+Setting block 2, was clear before
+tst_bitmaps: dump_bb
+block bitmap: 03000000000000000000000000000000
+bits set: 2
+tst_bitmaps: setb 3
+Setting block 3, was clear before
+tst_bitmaps: dump_bb
+block bitmap: 07000000000000000000000000000000
+bits set: 3
+tst_bitmaps: setb 4
+Setting block 4, was clear before
+tst_bitmaps: dump_bb
+block bitmap: 0f000000000000000000000000000000
+bits set: 4
+tst_bitmaps: setb 5
+Setting block 5, was clear before
+tst_bitmaps: dump_bb
+block bitmap: 1f000000000000000000000000000000
+bits set: 5
+tst_bitmaps: setb 6
+Setting block 6, was clear before
+tst_bitmaps: dump_bb
+block bitmap: 3f000000000000000000000000000000
+bits set: 6
+tst_bitmaps: setb 7
+Setting block 7, was clear before
+tst_bitmaps: dump_bb
+block bitmap: 7f000000000000000000000000000000
+bits set: 7
+tst_bitmaps: setb 8
+Setting block 8, was clear before
+tst_bitmaps: dump_bb
+block bitmap: ff000000000000000000000000000000
+bits set: 8
+tst_bitmaps: setb 10
+Setting block 10, was clear before
+tst_bitmaps: setb 12
+Setting block 12, was clear before
+tst_bitmaps: setb 14
+Setting block 14, was clear before
+tst_bitmaps: setb 17
+Setting block 17, was clear before
+tst_bitmaps: setb 19
+Setting block 19, was clear before
+tst_bitmaps: setb 24
+Setting block 24, was clear before
+tst_bitmaps: setb 26
+Setting block 26, was clear before
+tst_bitmaps: setb 27
+Setting block 27, was clear before
+tst_bitmaps: setb 30
+Setting block 30, was clear before
+tst_bitmaps: setb 31
+Setting block 31, was clear before
+tst_bitmaps: setb 32
+Setting block 32, was clear before
+tst_bitmaps: setb 35
+Setting block 35, was clear before
+tst_bitmaps: setb 39
+Setting block 39, was clear before
+tst_bitmaps: setb 40
+Setting block 40, was clear before
+tst_bitmaps: setb 44
+Setting block 44, was clear before
+tst_bitmaps: setb 46
+Setting block 46, was clear before
+tst_bitmaps: setb 47
+Setting block 47, was clear before
+tst_bitmaps: setb 49
+Setting block 49, was clear before
+tst_bitmaps: setb 51
+Setting block 51, was clear before
+tst_bitmaps: setb 52
+Setting block 52, was clear before
+tst_bitmaps: clearb 2
+Clearing block 2, was set before
+tst_bitmaps: clearb 3
+Clearing block 3, was set before
+tst_bitmaps: clearb 7
+Clearing block 7, was set before
+tst_bitmaps: dump_bb
+block bitmap: b92a85e6c4680d000000000000000000
+bits set: 25
tst_bitmaps: quit
tst_bitmaps:
--
1.7.12.rc0.22.gcdd159b
--
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