Add generic read_table function similar to write_table

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

1 files changed, 79 insertions, 0 deletions

diff --git a/lib/sqfs/read_table.c b/lib/sqfs/read_table.c
new file mode 100644
index 0000000..8fc8ebf
--- /dev/null
+++ b/lib/sqfs/read_table.c
@@ -0,0 +1,79 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "config.h"
+
+#include "meta_reader.h"
+#include "highlevel.h"
+#include "util.h"
+
+#include <endian.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+void *sqfs_read_table(int fd, compressor_t *cmp, size_t table_size,
+		      uint64_t location)
+{
+	size_t diff, block_count, list_size, blk_idx = 0;
+	uint64_t start, *locations;
+	meta_reader_t *m;
+	void *data, *ptr;
+
+	data = malloc(table_size);
+	if (data == NULL) {
+		perror("reading table");
+		return NULL;
+	}
+
+	/* restore list from image */
+	block_count = table_size / SQFS_META_BLOCK_SIZE;
+
+	if ((table_size % SQFS_META_BLOCK_SIZE) != 0)
+		++block_count;
+
+	list_size = sizeof(uint64_t) * block_count;
+	locations = malloc(list_size);
+
+	if (locations == NULL) {
+		perror("allocation table location list");
+		goto fail_data;
+	}
+
+	if (read_data_at("reading table locations", location,
+			 fd, locations, list_size)) {
+		goto fail_idx;
+	}
+
+	/* Read the actual data */
+	m = meta_reader_create(fd, cmp);
+	if (m == NULL)
+		goto fail_idx;
+
+	ptr = data;
+
+	while (table_size > 0) {
+		start = le64toh(locations[blk_idx++]);
+
+		if (meta_reader_seek(m, start, 0))
+			goto fail;
+
+		diff = SQFS_META_BLOCK_SIZE;
+		if (diff > table_size)
+			diff = table_size;
+
+		if (meta_reader_read(m, ptr, diff))
+			goto fail;
+
+		ptr = (char *)ptr + diff;
+		table_size -= diff;
+	}
+
+	meta_reader_destroy(m);
+	free(locations);
+	return data;
+fail:
+	meta_reader_destroy(m);
+fail_idx:
+	free(locations);
+fail_data:
+	free(data);
+	return NULL;
+}