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);
if (!set_next_cluster(ef, IS_CONTIGUOUS(*node), last,
EXFAT_CLUSTER_END))
return -EIO;
}
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);
if (!set_next_cluster(ef, IS_CONTIGUOUS(*node), previous,
EXFAT_CLUSTER_FREE))
return -EIO;
free_cluster(ef, previous);
previous = next;
}
return 0;
}
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 bool make_noncontiguous(const struct exfat* ef, cluster_t first,
cluster_t last)
{
cluster_t c;
for (c = first; c < last; c++)
if (!set_next_cluster(ef, false, c, c + 1))
return false;
return true;
}