1 files changed, 428 insertions, 0 deletions

diff --git a/exfat/cluster.c b/exfat/cluster.c
new file mode 100644
index 000000000..6b0303df8
--- /dev/null
+++ b/exfat/cluster.c
@@ -0,0 +1,428 @@
+/*
+	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;
+}