Cleanup: split "dir.h" into "dir_reader.h" and "dir_writer.h"

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

1 files changed, 237 insertions, 0 deletions

diff --git a/include/sqfs/dir_writer.h b/include/sqfs/dir_writer.h
new file mode 100644
index 0000000..09869a1
--- /dev/null
+++ b/include/sqfs/dir_writer.h
@@ -0,0 +1,237 @@
+/* SPDX-License-Identifier: LGPL-3.0-or-later */
+/*
+ * dir_writer.h - This file is part of libsquashfs
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser 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 Lesser General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+#ifndef SQFS_DIR_WRITER_H
+#define SQFS_DIR_WRITER_H
+
+#include "sqfs/predef.h"
+
+/**
+ * @file dir_writer.h
+ *
+ * @brief Contains declarations for the @ref sqfs_dir_writer_t.
+ */
+
+/**
+ * @struct sqfs_dir_writer_t
+ *
+ * @brief Abstracts generating of directory entries
+ *
+ * SquashFS stores directory entries and inodes seperated from each other. The
+ * inodes are stored in a series of meta data blocks before another series of
+ * meta data blocks that contain the directory entries. Directory inodes point
+ * to meta data block (and offset) where its contents are listed and the
+ * entries in turn point back to the inodes that represent them.
+ *
+ * There are some rules to this. Directory entries have to be written in
+ * ASCIIbetical ordering. Up to 256 entries are preceeded by a header. The
+ * entries use delta encoding for inode numbers and block locations relative to
+ * the header, so every time the inodes cross a meta data block boundary, if
+ * the difference in inode number gets too large, or if the entry count would
+ * exceed 256, a new header has to be emitted. Even if the inode pointed to is
+ * an extended type, the entry in the header still has to indicate the base
+ * type.
+ *
+ * In addtion to that, extended directory inodes can contain an index for
+ * faster lookup. The index points to each header and requires a new header to
+ * be emitted if the entries cross a block boundary.
+ *
+ * The dir writer takes care of all of this and provides a simple interface for
+ * adding entries. Internally it fills data into a meta data writer and
+ * generates an index that it can, on request, write to another meta data
+ * writer used for inodes.
+ */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief Create a directory writer.
+ *
+ * @memberof sqfs_dir_writer_t
+ *
+ * @param dm A pointer to a meta data writer that the generated directory
+ *           entries should be written to.
+ *
+ * @return A pointer to a directory writer on success, NULL on
+ *         allocation failure.
+ */
+SQFS_API sqfs_dir_writer_t *sqfs_dir_writer_create(sqfs_meta_writer_t *dm);
+
+/**
+ * @brief Destroy a directory writer and free all its memory.
+ *
+ * @memberof sqfs_dir_writer_t
+ *
+ * @param writer A pointer to a directory writer object.
+ */
+SQFS_API void sqfs_dir_writer_destroy(sqfs_dir_writer_t *writer);
+
+/**
+ * @brief Begin writing a directory, i.e. reset and initialize all internal
+ *        state neccessary.
+ *
+ * @memberof sqfs_dir_writer_t
+ *
+ * @param writer A pointer to a directory writer object.
+ *
+ * @return Zero on success, a @ref E_SQFS_ERROR value on failure.
+ */
+SQFS_API int sqfs_dir_writer_begin(sqfs_dir_writer_t *writer);
+
+/**
+ * @brief Add add a directory entry.
+ *
+ * @memberof sqfs_dir_writer_t
+ *
+ * @param writer A pointer to a directory writer object.
+ * @param name The name of the directory entry.
+ * @param inode_num The inode number of the entry.
+ * @param inode_ref A reference to the inode, i.e. the meta data block offset
+ *                  is stored in bits 16 to 48 and the lower 16 bit hold an
+ *                  offset into the block.
+ * @param mode A file mode, i.e. type and permission bits from which the entry
+ *             type is derived internally.
+ *
+ * @return Zero on success, a @ref E_SQFS_ERROR value on failure.
+ */
+SQFS_API int sqfs_dir_writer_add_entry(sqfs_dir_writer_t *writer,
+				       const char *name,
+				       uint32_t inode_num, uint64_t inode_ref,
+				       mode_t mode);
+
+/**
+ * @brief Finish writing a directory listing and write everything out to the
+ *        meta data writer.
+ *
+ * @memberof sqfs_dir_writer_t
+ *
+ * @param writer A pointer to a directory writer object.
+ *
+ * @return Zero on success, a @ref E_SQFS_ERROR value on failure.
+ */
+SQFS_API int sqfs_dir_writer_end(sqfs_dir_writer_t *writer);
+
+/**
+ * @brief Get the total, uncompressed size of the last written
+ *        directory in bytes.
+ *
+ * @memberof sqfs_dir_writer_t
+ *
+ * Call this function after @ref sqfs_dir_writer_end to get the uncompressed
+ * size of the directory listing that is required for the directory inodes.
+ * And also to determine which kind of directory inode to create.
+ *
+ * @param writer A pointer to a directory writer object.
+ *
+ * @return The size of the entire, uncompressed listing in bytes.
+ */
+SQFS_API size_t sqfs_dir_writer_get_size(const sqfs_dir_writer_t *writer);
+
+/**
+ * @brief Get the numer of entries written to the last directory.
+ *
+ * @memberof sqfs_dir_writer_t
+ *
+ * Call this function after @ref sqfs_dir_writer_end to get the total
+ * number of entries written to the directory.
+ *
+ * @param writer A pointer to a directory writer object.
+ *
+ * @return The number of entries in the directory.
+ */
+SQFS_API
+size_t sqfs_dir_writer_get_entry_count(const sqfs_dir_writer_t *writer);
+
+/**
+ * @brief Get the location of the last written directory.
+ *
+ * @memberof sqfs_dir_writer_t
+ *
+ * Call this function after @ref sqfs_dir_writer_end to get the location of
+ * the directory listing that is required for the directory inodes.
+ *
+ * @param writer A pointer to a directory writer object.
+ *
+ * @return A meta data reference, i.e. bits 16 to 48 contain the block start
+ *         and the lower 16 bit an offset into the uncompressed block.
+ */
+SQFS_API uint64_t
+sqfs_dir_writer_get_dir_reference(const sqfs_dir_writer_t *writer);
+
+/**
+ * @brief Get the size of the index of the last written directory.
+ *
+ * @memberof sqfs_dir_writer_t
+ *
+ * Call this function after @ref sqfs_dir_writer_end to get the size of
+ * the directory index that is required for extended directory inodes.
+ *
+ * @param writer A pointer to a directory writer object.
+ *
+ * @return The number of index entries.
+ */
+SQFS_API size_t sqfs_dir_writer_get_index_size(const sqfs_dir_writer_t *writer);
+
+/**
+ * @brief Write the index of the index of the last written directory to
+ *        a meta data writer after the extended directory inode.
+ *
+ * @memberof sqfs_dir_writer_t
+ *
+ * @param writer A pointer to a directory writer object.
+ * @param im A pointer to a meta data writer to write the index to.
+ *
+ * @return Zero on success, a @ref E_SQFS_ERROR value on failure.
+ */
+SQFS_API int sqfs_dir_writer_write_index(const sqfs_dir_writer_t *writer,
+					 sqfs_meta_writer_t *im);
+
+/**
+ * @brief Helper function for creating an inode from the last directory.
+ *
+ * @memberof sqfs_dir_writer_t
+ *
+ * Call this function after @ref sqfs_dir_writer_end to create a bare bones
+ * inode structure for the directory. The directory information is filled in
+ * completely and the type is set, the rest of the basic information such as
+ * permission bits, owner and timestamp is left untouched.
+ *
+ * If the generated inode is an extended directory inode, you can use another
+ * convenience function called @ref sqfs_dir_writer_write_index to write the
+ * index meta data after writing the inode itself.
+ *
+ * @param writer A pointer to a directory writer object.
+ * @param hlinks The number of hard links pointing to the directory.
+ * @param xattr If set to something other than 0xFFFFFFFF, an extended
+ *              directory inode is created with xattr index set.
+ * @param parent_ino The inode number of the parent directory.
+ *
+ * @return A generic inode or NULL on allocation failure.
+ */
+SQFS_API sqfs_inode_generic_t
+*sqfs_dir_writer_create_inode(const sqfs_dir_writer_t *writer, size_t hlinks,
+			      uint32_t xattr, uint32_t parent_ino);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* SQFS_DIR_WRITER_H */