/*
cluster.c (03.09.09)
exFAT file system implementation library.
Copyright (C) 2010-2012 Andrew Nayenko
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "exfat.h"
#include <errno.h>
#include <string.h>
/*
* Sector to absolute offset.
*/
static off64_t s2o(const struct exfat* ef, off64_t sector)
{
return sector << ef->sb->sector_bits;
}
/*
* Cluster to sector.
*/
static off64_t c2s(const struct exfat* ef, cluster_t cluster)
{
if (cluster < EXFAT_FIRST_DATA_CLUSTER)
exfat_bug("invalid cluster number %u", cluster);
return le32_to_cpu(ef->sb->cluster_sector_start) +
((off64_t) (cluster - EXFAT_FIRST_DATA_CLUSTER) << ef->sb->spc_bits);
}
/*
* Cluster to absolute offset.
*/
off64_t exfat_c2o(const struct exfat* ef, cluster_t cluster)
{
return s2o(ef, c2s(ef, cluster));
}
/*
* Sector to cluster.
*/
static cluster_t s2c(const struct exfat* ef, off64_t sector)
{
return ((sector - le32_to_cpu(ef->sb->cluster_sector_start)) >>
ef->sb->spc_bits) + EXFAT_FIRST_DATA_CLUSTER;
}
/*
* Size in bytes to size in clusters (rounded upwards).
*/
static uint32_t bytes2clusters(const struct exfat* ef, uint64_t bytes)
{
uint64_t cluster_size = CLUSTER_SIZE(*ef->sb);
return (bytes + cluster_size - 1) / cluster_size;
}
cluster_t exfat_next_cluster(const struct exfat* ef,
const struct exfat_node* node, cluster_t cluster)
{
le32_t next;
off64_t fat_offset;
if (cluster < EXFAT_FIRST_DATA_CLUSTER)
exfat_bug("bad cluster 0x%x", cluster);
if (IS_CONTIGUOUS(*node))
return cluster + 1;
fat_offset = s2o(ef, le32_to_cpu(ef->sb->fat_sector_start))
+ cluster * sizeof(cluster_t);
exfat_pread(ef->dev, &next, sizeof(next), fat_offset);
return le32_to_cpu(next);
}
cluster_t exfat_advance_cluster(const struct exfat* ef,
struct exfat_node* node, uint32_t count)
{
uint32_t i;
if (node->fptr_index > count)
{
node->fptr_index = 0;
node->fptr_cluster = node->start_cluster;
}
for (i = node->fptr_index; i < count; i++)
{
node->fptr_cluster = exfat_next_cluster(ef, node, node->fptr_cluster);
if (CLUSTER_INVALID(node->fptr_cluster))
break; /* the caller should handle this and print appropriate
error message */
}
node->fptr_index = count;
return node->fptr_cluster;
}
static cluster_t find_bit_and_set(uint8_t* bitmap, size_t start, size_t end)
{
const size_t start_index = start / 8;
const size_t end_index = DIV_ROUND_UP(end, 8);
size_t i;
size_t c;
for (i = start_index; i < end_index; i++)
{
if (bitmap[i] == 0xff)
continue;
for (c = MAX(i * 8, start); c < MIN((i + 1) * 8, end); c++)
if (BMAP_GET(bitmap, c) == 0)
{
BMAP_SET(bitmap, c);
return c + EXFAT_FIRST_DATA_CLUSTER;
}
}
return EXFAT_CLUSTER_END;
}
void exfat_flush_cmap(struct exfat* ef)
{
exfat_pwrite(ef->dev, ef->cmap.chunk, (ef->cmap.chunk_size + 7) / 8,
exfat_c2o(ef, ef->cmap.start_cluster));
ef->cmap.dirty = false;
}
static void set_next_cluster(const struct exfat* ef, int contiguous,
cluster_t current, cluster_t next)
{
off64_t fat_offset;
le32_t next_le32;
if (contiguous)
return;
fat_offset = s2o(ef, le32_to_cpu(ef->sb->fat_sector_start))
+ current * sizeof(cluster_t);
next_le32 = cpu_to_le32(next);
exfat_pwrite(ef->dev, &next_le32, sizeof(next_le32), fat_offset);
}
static cluster_t allocate_cluster(struct exfat* ef, cluster_t hint)
{
cluster_t cluster;
hint -= EXFAT_FIRST_DATA_CLUSTER;
if (hint >= ef->cmap.chunk_size)
hint = 0;
cluster = find_bit_and_set(ef->cmap.chunk, hint, ef->cmap.chunk_size);
if (cluster == EXFAT_CLUSTER_END)
cluster = find_bit_and_set(ef->cmap.chunk, 0, hint);
if (cluster == EXFAT_CLUSTER_END)
{
exfat_error("no free space left");
return EXFAT_CLUSTER_END;
}
ef->cmap.dirty = true;
return cluster;
}
static void free_cluster(struct exfat* ef, cluster_t cluster)
{
if (CLUSTER_INVALID(cluster))
exfat_bug("freeing invalid cluster 0x%x", cluster);
if (cluster - EXFAT_FIRST_DATA_CLUSTER >= ef->cmap.size)
exfat_bug("freeing non-existing cluster 0x%x (0x%x)", cluster,
ef->cmap.size);
BMAP_CLR(ef->cmap.chunk, cluster - EXFAT_FIRST_DATA_CLUSTER);
ef->cmap.dirty = true;
}
static void make_noncontiguous(const struct exfat* ef, cluster_t first,
cluster_t last)
{
cluster_t c;
for (c = first; c < last; c++)
set_next_cluster(ef, 0, c, c + 1);
}
static int shrink_file(struct exfat* ef, struct exfat_node* node,
uint32_t current, uint32_t difference);
static int grow_file(struct exfat* ef, struct exfat_node* node,
uint32_t current, uint32_t difference)
{
cluster_t previous;
cluster_t next;
uint32_t allocated = 0;
if (difference == 0)
exfat_bug("zero clusters count passed");
if (node->start_cluster != EXFAT_CLUSTER_FREE)
{
/* get the last cluster of the file */
previous = exfat_advance_cluster(ef, node, current - 1);
if (CLUSTER_INVALID(previous))
{
exfat_error("invalid cluster 0x%x while growing", previous);
return -EIO;
}
}
else
{
if (node->fptr_index != 0)
exfat_bug("non-zero pointer index (%u)", node->fptr_index);
/* file does not have clusters (i.e. is empty), allocate
the first one for it */
previous = allocate_cluster(ef, 0);
if (CLUSTER_INVALID(previous))
return -ENOSPC;
node->fptr_cluster = node->start_cluster = previous;
allocated = 1;
/* file consists of only one cluster, so it's contiguous */
node->flags |= EXFAT_ATTRIB_CONTIGUOUS;
}
while (allocated < difference)
{
next = allocate_cluster(ef, previous + 1);
if (CLUSTER_INVALID(next))
{
if (allocated != 0)
shrink_file(ef, node, current + allocated, allocated);
return -ENOSPC;
}
if (next != previous - 1 && IS_CONTIGUOUS(*node))
{
/* it's a pity, but we are not able to keep the file contiguous
anymore */
make_noncontiguous(ef, node->start_cluster, previous);
node->flags &= ~EXFAT_ATTRIB_CONTIGUOUS;
node->flags |= EXFAT_ATTRIB_DIRTY;
}
set_next_cluster(ef, IS_CONTIGUOUS(*node), previous, next);
previous = next;
allocated++;
}
set_next_cluster(ef, IS_CONTIGUOUS(*node), previous, EXFAT_CLUSTER_END);
return 0;
}
static int shrink_file(struct exfat* ef, struct exfat_node* node,
uint32_t current, uint32_t difference)
{
cluster_t previous;
cluster_t next;
if (difference == 0)
exfat_bug("zero difference passed");
if (node->start_cluster == EXFAT_CLUSTER_FREE)
exfat_bug("unable to shrink empty file (%u clusters)", current);
if (current < difference)
exfat_bug("file underflow (%u < %u)", current, difference);
/* crop the file */
if (current > difference)
{
cluster_t last = exfat_advance_cluster(ef, node,
current - difference - 1);
if (CLUSTER_INVALID(last))
{
exfat_error("invalid cluster 0x%x while shrinking", last);
return -EIO;
}
previous = exfat_next_cluster(ef, node, last);
set_next_cluster(ef, IS_CONTIGUOUS(*node), last, EXFAT_CLUSTER_END);
}
else
{
previous = node->start_cluster;
node->start_cluster = EXFAT_CLUSTER_FREE;
}
node->fptr_index = 0;
node->fptr_cluster = node->start_cluster;
/* free remaining clusters */
while (difference--)
{
if (CLUSTER_INVALID(previous))
{
exfat_error("invalid cluster 0x%x while freeing after shrink",
previous);
return -EIO;
}
next = exfat_next_cluster(ef, node, previous);
set_next_cluster(ef, IS_CONTIGUOUS(*node), previous,
EXFAT_CLUSTER_FREE);
free_cluster(ef, previous);
previous = next;
}
return 0;
}
static void erase_raw(struct exfat* ef, size_t size, off64_t offset)
{
exfat_pwrite(ef->dev, ef->zero_cluster, size, offset);
}
static int erase_range(struct exfat* ef, struct exfat_node* node,
uint64_t begin, uint64_t end)
{
uint64_t cluster_boundary;
cluster_t cluster;
if (begin >= end)
return 0;
cluster_boundary = (begin | (CLUSTER_SIZE(*ef->sb) - 1)) + 1;
cluster = exfat_advance_cluster(ef, node,
begin / CLUSTER_SIZE(*ef->sb));
if (CLUSTER_INVALID(cluster))
{
exfat_error("invalid cluster 0x%x while erasing", cluster);
return -EIO;
}
/* erase from the beginning to the closest cluster boundary */
erase_raw(ef, MIN(cluster_boundary, end) - begin,
exfat_c2o(ef, cluster) + begin % CLUSTER_SIZE(*ef->sb));
/* erase whole clusters */
while (cluster_boundary < end)
{
cluster = exfat_next_cluster(ef, node, cluster);
/* the cluster cannot be invalid because we have just allocated it */
if (CLUSTER_INVALID(cluster))
exfat_bug("invalid cluster 0x%x after allocation", cluster);
erase_raw(ef, CLUSTER_SIZE(*ef->sb), exfat_c2o(ef, cluster));
cluster_boundary += CLUSTER_SIZE(*ef->sb);
}
return 0;
}
int exfat_truncate(struct exfat* ef, struct exfat_node* node, uint64_t size)
{
uint32_t c1 = bytes2clusters(ef, node->size);
uint32_t c2 = bytes2clusters(ef, size);
int rc = 0;
if (node->references == 0 && node->parent)
exfat_bug("no references, node changes can be lost");
if (node->size == size)
return 0;
if (c1 < c2)
rc = grow_file(ef, node, c1, c2 - c1);
else if (c1 > c2)
rc = shrink_file(ef, node, c1, c1 - c2);
if (rc != 0)
return rc;
rc = erase_range(ef, node, node->size, size);
if (rc != 0)
return rc;
exfat_update_mtime(node);
node->size = size;
node->flags |= EXFAT_ATTRIB_DIRTY;
return 0;
}
uint32_t exfat_count_free_clusters(const struct exfat* ef)
{
uint32_t free_clusters = 0;
uint32_t i;
for (i = 0; i < ef->cmap.size; i++)
if (BMAP_GET(ef->cmap.chunk, i) == 0)
free_clusters++;
return free_clusters;
}
static int find_used_clusters(const struct exfat* ef,
cluster_t* a, cluster_t* b)
{
const cluster_t end = le32_to_cpu(ef->sb->cluster_count);
/* find first used cluster */
for (*a = *b + 1; *a < end; (*a)++)
if (BMAP_GET(ef->cmap.chunk, *a - EXFAT_FIRST_DATA_CLUSTER))
break;
if (*a >= end)
return 1;
/* find last contiguous used cluster */
for (*b = *a; *b < end; (*b)++)
if (BMAP_GET(ef->cmap.chunk, *b - EXFAT_FIRST_DATA_CLUSTER) == 0)
{
(*b)--;
break;
}
return 0;
}
int exfat_find_used_sectors(const struct exfat* ef, off64_t* a, off64_t* b)
{
cluster_t ca, cb;
if (*a == 0 && *b == 0)
ca = cb = EXFAT_FIRST_DATA_CLUSTER - 1;
else
{
ca = s2c(ef, *a);
cb = s2c(ef, *b);
}
if (find_used_clusters(ef, &ca, &cb) != 0)
return 1;
if (*a != 0 || *b != 0)
*a = c2s(ef, ca);
*b = c2s(ef, cb) + (CLUSTER_SIZE(*ef->sb) - 1) / SECTOR_SIZE(*ef->sb);
return 0;
}
