3 exFAT file system implementation library.
5 Copyright (C) 2009, 2010 Andrew Nayenko
7 This program is free software: you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation, either version 3 of the License, or
10 (at your option) any later version.
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>.
25 #define BMAP_GET(bitmap, index) ((bitmap)[(index) / 8] & (1u << ((index) % 8)))
26 #define BMAP_SET(bitmap, index) (bitmap)[(index) / 8] |= (1u << ((index) % 8))
27 #define BMAP_CLR(bitmap, index) (bitmap)[(index) / 8] &= ~(1u << ((index) % 8))
32 static uint32_t c2b(const struct exfat* ef, cluster_t cluster)
34 if (cluster < EXFAT_FIRST_DATA_CLUSTER)
35 exfat_bug("invalid cluster number %u", cluster);
36 return le32_to_cpu(ef->sb->cluster_block_start) +
37 ((cluster - EXFAT_FIRST_DATA_CLUSTER) << ef->sb->bpc_bits);
41 * Cluster to absolute offset.
43 off_t exfat_c2o(const struct exfat* ef, cluster_t cluster)
45 return (off_t) c2b(ef, cluster) << ef->sb->block_bits;
49 * Block to absolute offset.
51 static off_t b2o(const struct exfat* ef, uint32_t block)
53 return (off_t) block << ef->sb->block_bits;
57 * Size in bytes to size in clusters (rounded upwards).
59 static uint32_t bytes2clusters(const struct exfat* ef, uint64_t bytes)
61 uint64_t cluster_size = CLUSTER_SIZE(*ef->sb);
62 return (bytes + cluster_size - 1) / cluster_size;
65 cluster_t exfat_next_cluster(const struct exfat* ef,
66 const struct exfat_node* node, cluster_t cluster)
71 if (cluster < EXFAT_FIRST_DATA_CLUSTER)
72 exfat_bug("bad cluster 0x%x", cluster);
74 if (IS_CONTIGUOUS(*node))
76 fat_offset = b2o(ef, le32_to_cpu(ef->sb->fat_block_start))
77 + cluster * sizeof(cluster_t);
78 exfat_read_raw(&next, sizeof(next), fat_offset, ef->fd);
82 cluster_t exfat_advance_cluster(const struct exfat* ef,
83 struct exfat_node* node, uint32_t count)
87 if (node->fptr_index > count)
90 node->fptr_cluster = node->start_cluster;
93 for (i = node->fptr_index; i < count; i++)
95 node->fptr_cluster = exfat_next_cluster(ef, node, node->fptr_cluster);
96 if (CLUSTER_INVALID(node->fptr_cluster))
99 node->fptr_index = count;
100 return node->fptr_cluster;
103 static cluster_t find_bit_and_set(uint8_t* bitmap, cluster_t start,
106 const cluster_t mid_start = (start + 7) / 8 * 8;
107 const cluster_t mid_end = end / 8 * 8;
111 for (c = start; c < mid_start; c++)
112 if (BMAP_GET(bitmap, c) == 0)
115 return c + EXFAT_FIRST_DATA_CLUSTER;
118 for (byte = mid_start / 8; byte < mid_end / 8; byte++)
119 if (bitmap[byte] != 0xff)
123 for (bit = 0; bit < 8; bit++)
124 if (!(bitmap[byte] & (1u << bit)))
126 bitmap[byte] |= (1u << bit);
127 return byte * 8 + bit + EXFAT_FIRST_DATA_CLUSTER;
131 for (c = mid_end; c < end; c++)
132 if (BMAP_GET(bitmap, c) == 0)
135 return c + EXFAT_FIRST_DATA_CLUSTER;
138 return EXFAT_CLUSTER_END;
141 void exfat_flush_cmap(struct exfat* ef)
143 exfat_write_raw(ef->cmap.chunk, (ef->cmap.chunk_size + 7) / 8,
144 exfat_c2o(ef, ef->cmap.start_cluster), ef->fd);
148 static void set_next_cluster(const struct exfat* ef, int contiguous,
149 cluster_t current, cluster_t next)
155 fat_offset = b2o(ef, le32_to_cpu(ef->sb->fat_block_start))
156 + current * sizeof(cluster_t);
157 exfat_write_raw(&next, sizeof(next), fat_offset, ef->fd);
160 static void erase_cluster(struct exfat* ef, cluster_t cluster)
162 const int block_size = BLOCK_SIZE(*ef->sb);
163 const int blocks_in_cluster = CLUSTER_SIZE(*ef->sb) / block_size;
166 for (i = 0; i < blocks_in_cluster; i++)
167 exfat_write_raw(ef->zero_block, block_size,
168 exfat_c2o(ef, cluster) + i * block_size, ef->fd);
171 static cluster_t allocate_cluster(struct exfat* ef, cluster_t hint)
175 hint -= EXFAT_FIRST_DATA_CLUSTER;
176 if (hint >= ef->cmap.chunk_size)
179 cluster = find_bit_and_set(ef->cmap.chunk, hint, ef->cmap.chunk_size);
180 if (cluster == EXFAT_CLUSTER_END)
181 cluster = find_bit_and_set(ef->cmap.chunk, 0, hint);
182 if (cluster == EXFAT_CLUSTER_END)
184 exfat_error("no free space left");
185 return EXFAT_CLUSTER_END;
188 erase_cluster(ef, cluster);
190 /* FIXME update percentage of used space */
194 static void free_cluster(struct exfat* ef, cluster_t cluster)
196 if (CLUSTER_INVALID(cluster))
197 exfat_bug("attempting to free invalid cluster");
198 if (cluster < EXFAT_FIRST_DATA_CLUSTER ||
199 cluster - EXFAT_FIRST_DATA_CLUSTER >= ef->cmap.size)
200 exfat_bug("bad cluster 0x%x (0x%x)", cluster, ef->cmap.size);
202 BMAP_CLR(ef->cmap.chunk, cluster - EXFAT_FIRST_DATA_CLUSTER);
204 /* FIXME update percentage of used space */
207 static void make_noncontiguous(const struct exfat* ef, cluster_t first,
212 for (c = first; c < last; c++)
213 set_next_cluster(ef, 0, c, c + 1);
216 static int grow_file(struct exfat* ef, struct exfat_node* node,
223 exfat_bug("zero clusters count passed");
225 if (node->start_cluster != EXFAT_CLUSTER_FREE)
227 /* get the last cluster of the file */
228 previous = exfat_advance_cluster(ef, node,
229 bytes2clusters(ef, node->size) - 1);
230 if (CLUSTER_INVALID(previous))
232 exfat_error("invalid cluster in file");
238 if (node->fptr_index != 0)
239 exfat_bug("non-zero pointer index (%u)", node->fptr_index);
240 /* file does not have clusters (i.e. is empty), allocate
241 the first one for it */
242 previous = allocate_cluster(ef, 0);
243 if (CLUSTER_INVALID(previous))
245 node->fptr_cluster = node->start_cluster = previous;
247 /* file consists of only one cluster, so it's contiguous */
248 node->flags |= EXFAT_ATTRIB_CONTIGUOUS;
253 next = allocate_cluster(ef, previous + 1);
254 if (CLUSTER_INVALID(next))
256 if (next != previous - 1 && IS_CONTIGUOUS(*node))
258 /* it's a pity, but we are not able to keep the file contiguous
260 make_noncontiguous(ef, node->start_cluster, previous);
261 node->flags &= ~EXFAT_ATTRIB_CONTIGUOUS;
263 set_next_cluster(ef, IS_CONTIGUOUS(*node), previous, next);
267 set_next_cluster(ef, IS_CONTIGUOUS(*node), previous, EXFAT_CLUSTER_END);
271 static int shrink_file(struct exfat* ef, struct exfat_node* node,
274 uint32_t current = bytes2clusters(ef, node->size);
279 exfat_bug("zero difference passed");
280 if (node->start_cluster == EXFAT_CLUSTER_FREE)
281 exfat_bug("unable to shrink empty file (%u clusters)", current);
282 if (current < difference)
283 exfat_bug("file underflow (%u < %u)", current, difference);
286 if (current > difference)
288 cluster_t last = exfat_advance_cluster(ef, node,
289 current - difference - 1);
290 if (CLUSTER_INVALID(last))
292 exfat_error("invalid cluster in file");
295 previous = exfat_next_cluster(ef, node, last);
296 set_next_cluster(ef, IS_CONTIGUOUS(*node), last, EXFAT_CLUSTER_END);
300 previous = node->start_cluster;
301 node->start_cluster = EXFAT_CLUSTER_FREE;
303 node->fptr_index = 0;
304 node->fptr_cluster = node->start_cluster;
306 /* free remaining clusters */
309 if (CLUSTER_INVALID(previous))
311 exfat_error("invalid cluster in file");
314 next = exfat_next_cluster(ef, node, previous);
315 set_next_cluster(ef, IS_CONTIGUOUS(*node), previous,
317 free_cluster(ef, previous);
323 int exfat_truncate(struct exfat* ef, struct exfat_node* node, uint64_t size)
325 uint32_t c1 = bytes2clusters(ef, node->size);
326 uint32_t c2 = bytes2clusters(ef, size);
330 rc = grow_file(ef, node, c2 - c1);
332 rc = shrink_file(ef, node, c1 - c2);
337 if (node->size != size)
339 exfat_update_mtime(node);
341 node->flags |= EXFAT_ATTRIB_DIRTY;