diff options
Diffstat (limited to 'lib/ext2fs/bitops.c')
-rw-r--r-- | lib/ext2fs/bitops.c | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/lib/ext2fs/bitops.c b/lib/ext2fs/bitops.c index 9322a353..8e4c05c4 100644 --- a/lib/ext2fs/bitops.c +++ b/lib/ext2fs/bitops.c @@ -116,3 +116,43 @@ 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 nbytes) +{ + const unsigned char *cp = addr; + const __u32 *p; + unsigned int res = 0; + + while (((((unsigned long) cp) & 3) != 0) && (nbytes > 0)) { + res += popcount8(*cp++); + nbytes--; + } + p = (const __u32 *) cp; + + while (nbytes > 4) { + res += popcount32(*p++); + nbytes -= 4; + } + cp = (const unsigned char *) p; + + while (nbytes > 0) { + res += popcount8(*cp++); + nbytes--; + } + return res; +} |