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/*
* extent.c --- ext2 extent abstraction
*
* This abstraction is used to provide a compact way of representing a
* translation table, for moving multiple contiguous ranges (extents)
* of blocks or inodes.
*
* Copyright (C) 1997, 1998 by Theodore Ts'o and
* PowerQuest, Inc.
*
* Copyright (C) 1999, 2000 by Theosore Ts'o
*
* %Begin-Header%
* This file may be redistributed under the terms of the GNU Public
* License.
* %End-Header%
*/
#include "resize2fs.h"
struct ext2_extent_entry {
__u32 old_loc, new_loc;
int size;
};
struct _ext2_extent {
struct ext2_extent_entry *list;
int cursor;
int size;
int num;
int sorted;
};
/*
* Create an extent table
*/
errcode_t ext2fs_create_extent_table(ext2_extent *ret_extent, int size)
{
ext2_extent extent;
errcode_t retval;
retval = ext2fs_get_mem(sizeof(struct _ext2_extent), &extent);
if (retval)
return retval;
memset(extent, 0, sizeof(struct _ext2_extent));
extent->size = size ? size : 50;
extent->cursor = 0;
extent->num = 0;
extent->sorted = 1;
retval = ext2fs_get_array(sizeof(struct ext2_extent_entry),
extent->size, &extent->list);
if (retval) {
ext2fs_free_mem(&extent);
return retval;
}
memset(extent->list, 0,
sizeof(struct ext2_extent_entry) * extent->size);
*ret_extent = extent;
return 0;
}
/*
* Free an extent table
*/
void ext2fs_free_extent_table(ext2_extent extent)
{
if (extent->list)
ext2fs_free_mem(&extent->list);
extent->list = 0;
extent->size = 0;
extent->num = 0;
ext2fs_free_mem(&extent);
}
/*
* Add an entry to the extent table
*/
errcode_t ext2fs_add_extent_entry(ext2_extent extent, __u32 old_loc, __u32 new_loc)
{
struct ext2_extent_entry *ent;
errcode_t retval;
int newsize;
int curr;
if (extent->num >= extent->size) {
newsize = extent->size + 100;
retval = ext2fs_resize_mem(sizeof(struct ext2_extent_entry) *
extent->size,
sizeof(struct ext2_extent_entry) *
newsize, &extent->list);
if (retval)
return retval;
extent->size = newsize;
}
curr = extent->num;
ent = extent->list + curr;
if (curr) {
/*
* Check to see if this can be coalesced with the last
* extent
*/
ent--;
if ((ent->old_loc + ent->size == old_loc) &&
(ent->new_loc + ent->size == new_loc)) {
ent->size++;
return 0;
}
/*
* Now see if we're going to ruin the sorting
*/
if (ent->old_loc + ent->size > old_loc)
extent->sorted = 0;
ent++;
}
ent->old_loc = old_loc;
ent->new_loc = new_loc;
ent->size = 1;
extent->num++;
return 0;
}
/*
* Helper function for qsort
*/
static EXT2_QSORT_TYPE extent_cmp(const void *a, const void *b)
{
const struct ext2_extent_entry *db_a;
const struct ext2_extent_entry *db_b;
db_a = (const struct ext2_extent_entry *) a;
db_b = (const struct ext2_extent_entry *) b;
return (db_a->old_loc - db_b->old_loc);
}
/*
* Given an inode map and inode number, look up the old inode number
* and return the new inode number.
*/
__u32 ext2fs_extent_translate(ext2_extent extent, __u32 old_loc)
{
int low, high, mid;
__u32 lowval, highval;
float range;
if (!extent->sorted) {
qsort(extent->list, extent->num,
sizeof(struct ext2_extent_entry), extent_cmp);
extent->sorted = 1;
}
low = 0;
high = extent->num-1;
while (low <= high) {
#if 0
mid = (low+high)/2;
#else
if (low == high)
mid = low;
else {
/* Interpolate for efficiency */
lowval = extent->list[low].old_loc;
highval = extent->list[high].old_loc;
if (old_loc < lowval)
range = 0;
else if (old_loc > highval)
range = 1;
else {
range = ((float) (old_loc - lowval)) /
(highval - lowval);
if (range > 0.9)
range = 0.9;
if (range < 0.1)
range = 0.1;
}
mid = low + ((int) (range * (high-low)));
}
#endif
if ((old_loc >= extent->list[mid].old_loc) &&
(old_loc < extent->list[mid].old_loc + extent->list[mid].size))
return (extent->list[mid].new_loc +
(old_loc - extent->list[mid].old_loc));
if (old_loc < extent->list[mid].old_loc)
high = mid-1;
else
low = mid+1;
}
return 0;
}
/*
* For debugging only
*/
void ext2fs_extent_dump(ext2_extent extent, FILE *out)
{
int i;
struct ext2_extent_entry *ent;
fputs(_("# Extent dump:\n"), out);
fprintf(out, _("#\tNum=%d, Size=%d, Cursor=%d, Sorted=%d\n"),
extent->num, extent->size, extent->cursor, extent->sorted);
for (i=0, ent=extent->list; i < extent->num; i++, ent++) {
fprintf(out, _("#\t\t %u -> %u (%d)\n"), ent->old_loc,
ent->new_loc, ent->size);
}
}
/*
* Iterate over the contents of the extent table
*/
errcode_t ext2fs_iterate_extent(ext2_extent extent, __u32 *old_loc,
__u32 *new_loc, int *size)
{
struct ext2_extent_entry *ent;
if (!old_loc) {
extent->cursor = 0;
return 0;
}
if (extent->cursor >= extent->num) {
*old_loc = 0;
*new_loc = 0;
*size = 0;
return 0;
}
ent = extent->list + extent->cursor++;
*old_loc = ent->old_loc;
*new_loc = ent->new_loc;
*size = ent->size;
return 0;
}
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