Add directory reader data structure

This moves a lot of the stuff that is done manually in the tree
deserializer to a generic helper in libsquashfs.

Due to how the fstree is implemented, as a work around, the inode needs
to be temporarily stored in the tree node, but some of the directory
details could be removed.

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

1 files changed, 266 insertions, 0 deletions

diff --git a/lib/sqfs/dir_reader.c b/lib/sqfs/dir_reader.c
new file mode 100644
index 0000000..d4bfd27
--- /dev/null
+++ b/lib/sqfs/dir_reader.c
@@ -0,0 +1,266 @@
+/* SPDX-License-Identifier: LGPL-3.0-or-later */
+/*
+ * fs_reader.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#define SQFS_BUILDING_DLL
+#include "config.h"
+
+#include "sqfs/meta_reader.h"
+#include "sqfs/compress.h"
+#include "sqfs/super.h"
+#include "sqfs/inode.h"
+#include "sqfs/error.h"
+#include "sqfs/dir.h"
+#include "util.h"
+
+#include <string.h>
+#include <stdlib.h>
+
+struct sqfs_dir_reader_t {
+	sqfs_meta_reader_t *meta_dir;
+	sqfs_meta_reader_t *meta_inode;
+	const sqfs_super_t *super;
+
+	sqfs_dir_header_t hdr;
+	uint64_t dir_block_start;
+	size_t entries;
+	size_t size;
+
+	size_t start_size;
+	uint16_t dir_offset;
+	uint16_t inode_offset;
+};
+
+sqfs_dir_reader_t *sqfs_dir_reader_create(const sqfs_super_t *super,
+					  sqfs_compressor_t *cmp,
+					  sqfs_file_t *file)
+{
+	sqfs_dir_reader_t *rd = calloc(1, sizeof(*rd));
+	uint64_t start, limit;
+
+	if (rd == NULL)
+		return NULL;
+
+	start = super->inode_table_start;
+	limit = super->directory_table_start;
+
+	rd->meta_inode = sqfs_meta_reader_create(file, cmp, start, limit);
+
+	if (rd->meta_inode == NULL) {
+		free(rd);
+		return NULL;
+	}
+
+	start = super->directory_table_start;
+	limit = super->id_table_start;
+
+	if (super->fragment_table_start < limit)
+		limit = super->fragment_table_start;
+
+	if (super->export_table_start < limit)
+		limit = super->export_table_start;
+
+	rd->meta_dir = sqfs_meta_reader_create(file, cmp, start, limit);
+
+	if (rd->meta_dir == NULL) {
+		sqfs_meta_reader_destroy(rd->meta_inode);
+		free(rd);
+		return NULL;
+	}
+
+	rd->super = super;
+	return rd;
+}
+
+void sqfs_dir_reader_destroy(sqfs_dir_reader_t *rd)
+{
+	sqfs_meta_reader_destroy(rd->meta_inode);
+	sqfs_meta_reader_destroy(rd->meta_dir);
+	free(rd);
+}
+
+int sqfs_dir_reader_open_dir(sqfs_dir_reader_t *rd,
+			     const sqfs_inode_generic_t *inode)
+{
+	uint64_t block_start;
+	size_t size, offset;
+
+	if (inode->base.type == SQFS_INODE_DIR) {
+		size = inode->data.dir.size;
+		offset = inode->data.dir.offset;
+		block_start = inode->data.dir.start_block;
+	} else if (inode->base.type == SQFS_INODE_EXT_DIR) {
+		size = inode->data.dir_ext.size;
+		offset = inode->data.dir_ext.offset;
+		block_start = inode->data.dir_ext.start_block;
+	} else {
+		return SQFS_ERROR_NOT_DIR;
+	}
+
+	memset(&rd->hdr, 0, sizeof(rd->hdr));
+	rd->size = size;
+	rd->entries = 0;
+
+	if (rd->size <= sizeof(rd->hdr))
+		return 0;
+
+	block_start += rd->super->directory_table_start;
+
+	rd->dir_block_start = block_start;
+	rd->dir_offset = offset;
+	rd->start_size = size;
+
+	return sqfs_meta_reader_seek(rd->meta_dir, block_start, offset);
+}
+
+int sqfs_dir_reader_read(sqfs_dir_reader_t *rd, sqfs_dir_entry_t **out)
+{
+	sqfs_dir_entry_t *ent;
+	size_t count;
+	int err;
+
+	if (!rd->entries) {
+		if (rd->size < sizeof(rd->hdr))
+			return 1;
+
+		err = sqfs_meta_reader_read_dir_header(rd->meta_dir, &rd->hdr);
+		if (err)
+			return err;
+
+		rd->size -= sizeof(rd->hdr);
+		rd->entries = rd->hdr.count + 1;
+	}
+
+	err = sqfs_meta_reader_read_dir_ent(rd->meta_dir, &ent);
+	if (err)
+		return err;
+
+	count = sizeof(*ent) + strlen((const char *)ent->name);
+
+	if (count > rd->size) {
+		rd->size = 0;
+		rd->entries = 0;
+	} else {
+		rd->size -= count;
+		rd->entries -= 1;
+	}
+
+	rd->inode_offset = ent->offset;
+	*out = ent;
+	return 0;
+}
+
+int sqfs_dir_reader_rewind(sqfs_dir_reader_t *rd)
+{
+	memset(&rd->hdr, 0, sizeof(rd->hdr));
+	rd->size = rd->start_size;
+	rd->entries = 0;
+
+	return sqfs_meta_reader_seek(rd->meta_dir, rd->dir_block_start,
+				     rd->dir_offset);
+}
+
+int sqfs_dir_reader_find(sqfs_dir_reader_t *rd, const char *name)
+{
+	sqfs_dir_entry_t *ent;
+	int ret;
+
+	if (rd->size != rd->start_size) {
+		ret = sqfs_dir_reader_rewind(rd);
+		if (ret)
+			return ret;
+	}
+
+	do {
+		ret = sqfs_dir_reader_read(rd, &ent);
+		if (ret < 0)
+			return ret;
+		if (ret > 0)
+			return SQFS_ERROR_NO_ENTRY;
+
+		ret = strcmp((const char *)ent->name, name);
+		free(ent);
+	} while (ret < 0);
+
+	return ret == 0 ? 0 : SQFS_ERROR_NO_ENTRY;
+}
+
+int sqfs_dir_reader_get_inode(sqfs_dir_reader_t *rd,
+			      sqfs_inode_generic_t **inode)
+{
+	uint64_t block_start;
+
+	block_start = rd->hdr.start_block;
+
+	return sqfs_meta_reader_read_inode(rd->meta_inode, rd->super,
+					   block_start, rd->inode_offset,
+					   inode);
+}
+
+int sqfs_dir_reader_get_root_inode(sqfs_dir_reader_t *rd,
+				   sqfs_inode_generic_t **inode)
+{
+	uint64_t block_start = rd->super->root_inode_ref >> 16;
+	uint16_t offset = rd->super->root_inode_ref & 0xFFFF;
+
+	return sqfs_meta_reader_read_inode(rd->meta_inode, rd->super,
+					   block_start, offset, inode);
+}
+
+int sqfs_dir_reader_find_by_path(sqfs_dir_reader_t *rd, const char *path,
+				 sqfs_inode_generic_t **out)
+{
+	sqfs_inode_generic_t *inode;
+	sqfs_dir_entry_t *ent;
+	const char *ptr;
+	int ret;
+
+	ret = sqfs_dir_reader_get_root_inode(rd, &inode);
+	if (ret)
+		return ret;
+
+	while (*path != '\0') {
+		if (*path == '/' || *path == '\\') {
+			while (*path == '/' || *path == '\\')
+				++path;
+			continue;
+		}
+
+		ret = sqfs_dir_reader_open_dir(rd, inode);
+		free(inode);
+		if (ret)
+			return ret;
+
+		ptr = strchr(path, '/');
+		if (ptr == NULL)
+			ptr = strchrnul(path, '\\');
+
+		do {
+			ret = sqfs_dir_reader_read(rd, &ent);
+			if (ret < 0)
+				return ret;
+
+			if (ret == 0) {
+				ret = strncmp((const char *)ent->name,
+					      path, ptr - path);
+				if (ret == 0)
+					ret = ent->name[ptr - path];
+				free(ent);
+			}
+		} while (ret < 0);
+
+		if (ret > 0)
+			return SQFS_ERROR_NO_ENTRY;
+
+		ret = sqfs_dir_reader_get_inode(rd, &inode);
+		if (ret)
+			return ret;
+
+		path = ptr;
+	}
+
+	*out = inode;
+	return 0;
+}