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Improved bit countings

N2009_11_14_FIXES
jpandre 2008-09-06 09:34:23 +00:00
parent 8b0358876a
commit a58ff9073d
2 changed files with 54 additions and 59 deletions
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21
libntfs-3g/attrib.c
View File

@ -5112,10 +5112,23 @@ s64 ntfs_attr_get_free_bits(ntfs_attr *na)
if (br <= 0)
break;
total += br;
for (i = 0; i < br; i++)
for (j = 0; j < 8; j++)
if (!((buf[i] >> j) & 1))
nr_free++;
for (i = 0; i < br; )
switch (buf[i]) {
case 0 :
do {
nr_free += 8;
} while ((++i < br) && (!buf[i]));
break;
case 255 :
do {
} while ((++i < br) && (buf[i] == 255));
break;
default :
for (j = 0; j < 8; j++)
if (!((buf[i] >> j) & 1))
nr_free++;
i++;
}
}
free(buf);
if (!total || br < 0)

92
libntfs-3g/lcnalloc.c
View File

@ -82,74 +82,56 @@ static void ntfs_cluster_update_zone_pos(ntfs_volume *vol, u8 zone, LCN tc)
static s64 max_empty_bit_range(unsigned char *buf, int size)
{
int max_range;
int i,j;
int run;
unsigned char uncounted;
int i, j, run = 0;
int max_range = 0;
s64 start_pos = -1;
max_range = 0;
ntfs_log_trace("Entering\n");
i = 0;
/*
* count every bit until we reach a range of 8
* (fast count if all bits set)
*/
run = 0;
while ((i < size) && (max_range < 8)) {
if (*buf == 255) {
while (i < size) {
switch (*buf) {
case 0 :
do {
buf++;
run += 8;
i++;
} while ((i < size) && !*buf);
break;
case 255 :
if (run > max_range) {
max_range = run;
start_pos = i * 8 - run;
start_pos = (s64)i * 8 - run;
}
run = 0;
} else
for (j=0; j<8; j++)
if (*buf & (1 << j)) {
do {
buf++;
i++;
} while ((i < size) && (*buf == 255));
break;
default :
for (j = 0; j < 8; j++) {
int bit = *buf & (1 << j);
if (bit) {
if (run > max_range) {
max_range = run;
start_pos = i * 8 + j - run;
start_pos = (s64)i * 8 + (j - run);
}
run = 0;
} else
} else
run++;
i++;
buf++;
}
/*
* From now on, beginning and end are in different bytes
* and we do not count bits unless we have enough
* null bytes
*/
uncounted = 255;
while (i < size) {
if (*buf) {
if ((run + 14) > max_range) {
/* uncounted bits in first byte */
for (j=7; (j>=0) && !(uncounted & (1 << j)); j--)
run++;
/* uncounted bits in last byte */
for (j=0; (j<8) && !(*buf & (1 << j)); j++)
run++;
if (run > max_range) {
max_range = run;
start_pos = i * 8 + j - run;
}
}
uncounted = *buf;
run = 0;
} else
run += 8;
buf++;
i++;
i++;
buf++;
}
}
if ((run + 7) > max_range) {
/* uncounted bits in first byte */
for (j=7; (j>=0) && !(uncounted & (1 << j)); j--)
run++;
if (run > max_range)
start_pos = i * 8 - run;
}
if (run > max_range)
start_pos = (s64)i * 8 - run;
return start_pos;
}