2 * extent.c --- ext2 extent abstraction
4 * This abstraction is used to provide a compact way of representing a
5 * translation table, for moving multiple contiguous ranges (extents)
8 * Copyright (C) 1997 Theodore Ts'o
11 * All rights reserved.
15 #include "resize2fs.h"
17 struct ext2_extent_entry {
18 __u32 old_loc, new_loc;
23 struct ext2_extent_entry *list;
31 * Create an extent table
33 errcode_t ext2fs_create_extent_table(ext2_extent *ret_extent, int size)
38 retval = ext2fs_get_mem(sizeof(struct _ext2_extent),
42 memset(extent, 0, sizeof(struct _ext2_extent));
44 extent->size = size ? size : 50;
49 retval = ext2fs_get_mem(sizeof(struct ext2_extent_entry) *
50 extent->size, (void **) &extent->list);
55 memset(extent->list, 0,
56 sizeof(struct ext2_extent_entry) * extent->size);
62 * Free an extent table
64 void ext2fs_free_extent_table(ext2_extent extent)
67 ext2fs_free_mem((void **) &extent->list);
71 ext2fs_free_mem((void **) &extent);
75 * Add an entry to the extent table
77 errcode_t ext2fs_add_extent_entry(ext2_extent extent, __u32 old_loc, __u32 new_loc)
79 struct ext2_extent_entry *ent;
84 if (extent->num >= extent->size) {
85 newsize = extent->size + 100;
86 retval = ext2fs_resize_mem(sizeof(struct ext2_extent_entry) *
87 newsize, (void **) &extent->list);
90 extent->size = newsize;
93 ent = extent->list + curr;
96 * Check to see if this can be coalesced with the last
100 if ((ent->old_loc + ent->size == old_loc) &&
101 (ent->new_loc + ent->size == new_loc)) {
106 * Now see if we're going to ruin the sorting
108 if (ent->old_loc + ent->size > old_loc)
112 ent->old_loc = old_loc;
113 ent->new_loc = new_loc;
120 * Helper function for qsort
122 static int extent_cmp(const void *a, const void *b)
124 const struct ext2_extent_entry *db_a;
125 const struct ext2_extent_entry *db_b;
127 db_a = (const struct ext2_extent_entry *) a;
128 db_b = (const struct ext2_extent_entry *) b;
130 return (db_a->old_loc - db_b->old_loc);
134 * Given an inode map and inode number, look up the old inode number
135 * and return the new inode number.
137 __u32 ext2fs_extent_translate(ext2_extent extent, __u32 old_loc)
140 ino_t lowval, highval;
143 if (!extent->sorted) {
144 qsort(extent->list, extent->num,
145 sizeof(struct ext2_extent_entry), extent_cmp);
149 high = extent->num-1;
150 while (low <= high) {
157 /* Interpolate for efficiency */
158 lowval = extent->list[low].old_loc;
159 highval = extent->list[high].old_loc;
161 if (old_loc < lowval)
163 else if (old_loc > highval)
166 range = ((float) (old_loc - lowval)) /
168 mid = low + ((int) (range * (high-low)));
171 if ((old_loc >= extent->list[mid].old_loc) &&
172 (old_loc < extent->list[mid].old_loc + extent->list[mid].size))
173 return (extent->list[mid].new_loc +
174 (old_loc - extent->list[mid].old_loc));
175 if (old_loc < extent->list[mid].old_loc)
186 void ext2fs_extent_dump(ext2_extent extent, FILE *out)
189 struct ext2_extent_entry *ent;
191 fputs("# Extent dump:\n", out);
192 fprintf(out, "#\tNum=%d, Size=%d, Cursor=%d, Sorted=%d\n",
193 extent->num, extent->size, extent->cursor, extent->sorted);
194 for (i=0, ent=extent->list; i < extent->num; i++, ent++) {
195 fprintf(out, "#\t\t %u -> %u (%d)\n", ent->old_loc,
196 ent->new_loc, ent->size);
201 * Iterate over the contents of the extent table
203 errcode_t ext2fs_iterate_extent(ext2_extent extent, __u32 *old_loc,
204 __u32 *new_loc, int *size)
206 struct ext2_extent_entry *ent;
213 if (extent->cursor >= extent->num) {
220 ent = extent->list + extent->cursor++;
222 *old_loc = ent->old_loc;
223 *new_loc = ent->new_loc;