unsquashfs: read ID table from file

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 96 insertions, 0 deletions

diff --git a/lib/sqfs/id_table_read.c b/lib/sqfs/id_table_read.c
new file mode 100644
index 0000000..b1305ff
--- /dev/null
+++ b/lib/sqfs/id_table_read.c
@@ -0,0 +1,96 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "meta_reader.h"
+#include "id_table.h"
+#include "table.h"
+#include "util.h"
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdio.h>
+
+int id_table_read(id_table_t *tbl, int fd, sqfs_super_t *super,
+		  compressor_t *cmp)
+{
+	size_t i, block_count, count, diff;
+	uint64_t blocks[32];
+	meta_reader_t *m;
+	uint32_t *ptr;
+	ssize_t ret;
+
+	if (tbl->ids != NULL) {
+		free(tbl->ids);
+		tbl->num_ids = 0;
+		tbl->max_ids = 0;
+		tbl->ids = NULL;
+	}
+
+	if (!super->id_count || super->id_table_start >= super->bytes_used) {
+		fputs("ID table missing from file system\n", stderr);
+		return -1;
+	}
+
+	tbl->ids = malloc(super->id_count * sizeof(uint32_t));
+	if (tbl->ids == NULL) {
+		perror("reading ID table");
+		return -1;
+	}
+
+	tbl->num_ids = super->id_count;
+	tbl->max_ids = super->id_count;
+
+	if (lseek(fd, super->id_table_start, SEEK_SET) == (off_t)-1)
+		goto fail_seek;
+
+	block_count = super->id_count / 2048;
+	if (super->id_count % 2048)
+		++block_count;
+
+	ret = read_retry(fd, blocks, sizeof(blocks[0]) * block_count);
+	if (ret < 0)
+		goto fail_rd;
+
+	if ((size_t)ret < sizeof(blocks[0]) * block_count)
+		goto fail_trunc;
+
+	for (i = 0; i < block_count; ++i)
+		blocks[i] = le64toh(blocks[i]);
+
+	m = meta_reader_create(fd, cmp);
+	if (m == NULL)
+		return -1;
+
+	count = super->id_count;
+	ptr = tbl->ids;
+
+	for (i = 0; i < block_count && count > 0; ++i) {
+		diff = count < 2048 ? count : 2048;
+
+		if (meta_reader_seek(m, blocks[i], 0))
+			goto fail_meta;
+
+		if (meta_reader_read(m, ptr, diff * sizeof(tbl->ids[0])))
+			goto fail_meta;
+
+		count -= diff;
+		ptr += diff;
+	}
+
+	meta_reader_destroy(m);
+
+	for (i = 0; i < tbl->num_ids; ++i)
+		tbl->ids[i] = le32toh(tbl->ids[i]);
+
+	return 0;
+fail_meta:
+	meta_reader_destroy(m);
+	return -1;
+fail_trunc:
+	fputs("reading ID table: unexpected end of file\n", stderr);
+	return -1;
+fail_rd:
+	perror("reading ID table");
+	return -1;
+fail_seek:
+	perror("seeking to ID table");
+	return -1;
+}