sqfs_id_table_t Struct Reference

A simple data structure that encapsulates ID to index mapping for user and group IDs. More...

#include <id_table.h>

Inheritance diagram for sqfs_id_table_t:

Collaboration diagram for sqfs_id_table_t:

Public Member Functions
SQFS_API sqfs_id_table_t *	sqfs_id_table_create (sqfs_u32 flags)
	Create an ID table object.
SQFS_API int	sqfs_id_table_id_to_index (sqfs_id_table_t *tbl, sqfs_u32 id, sqfs_u16 *out)
	Resolve a 32 bit ID to a unique 16 bit index.
SQFS_API int	sqfs_id_table_write (sqfs_id_table_t *tbl, sqfs_file_t *file, sqfs_super_t *super, sqfs_compressor_t *cmp)
	Write an ID table to disk.
SQFS_API int	sqfs_id_table_read (sqfs_id_table_t *tbl, sqfs_file_t *file, const sqfs_super_t *super, sqfs_compressor_t *cmp)
	Read an ID table from disk.
SQFS_API int	sqfs_id_table_index_to_id (const sqfs_id_table_t *tbl, sqfs_u16 index, sqfs_u32 *out)
	Resolve a 16 bit index to a 32 bit ID.

Additional Inherited Members
Static Public Member Functions inherited from sqfs_object_t
static SQFS_INLINE void	sqfs_destroy (void *obj)
	Destroy an object and free all its memory.
static SQFS_INLINE void *	sqfs_copy (const void *obj)
	Create a deep copy of an object if possible.
Data Fields inherited from sqfs_object_t
void(*	destroy )(struct sqfs_object_t *instance)
struct sqfs_object_t *(*	copy )(const struct sqfs_object_t *orig)

Detailed Description

A simple data structure that encapsulates ID to index mapping for user and group IDs.

SquashFS does not store user and group IDs in inodes directly. Instead, it collects the unique 32 bit IDs in a table with at most 64k entries and stores a 16 bit index into the inode. This allows SquashFS to only have 16 bit UID/GID entries in the inodes but actually have 32 bit UIDs/GIDs under the hood (at least 64k selected ones).

Examples

list_files.c.

Member Function Documentation

sqfs_id_table_create()

SQFS_API sqfs_id_table_t * sqfs_id_table_create

(

sqfs_u32

flags

)

Create an ID table object.

Parameters

flags

Currently must be set to 0 or creating the table fails.

Returns

A pointer to an ID table object, NULL on allocation failure.

sqfs_id_table_id_to_index()

SQFS_API int sqfs_id_table_id_to_index	(	sqfs_id_table_t *	tbl,
		sqfs_u32	id,
		sqfs_u16 *	out
	)

Resolve a 32 bit ID to a unique 16 bit index.

Parameters

tbl	A pointer to an ID table object.
id	The ID to resolve.
out	Returns the unique table index.

Returns

Zero on success, an SQFS_ERROR on failure.

sqfs_id_table_index_to_id()

SQFS_API int sqfs_id_table_index_to_id	(	const sqfs_id_table_t *	tbl,
		sqfs_u16	index,
		sqfs_u32 *	out
	)

Resolve a 16 bit index to a 32 bit ID.

Parameters

tbl	A pointer to an ID table object.
index	The table index to resolve.
out	Returns the underlying 32 bit ID that the index maps to.

Returns

Zero on success, an SQFS_ERROR on failure.

sqfs_id_table_read()

SQFS_API int sqfs_id_table_read	(	sqfs_id_table_t *	tbl,
		sqfs_file_t *	file,
		const sqfs_super_t *	super,
		sqfs_compressor_t *	cmp
	)

Read an ID table from disk.

Parameters

tbl	A pointer to an ID table object.
file	The underlying file to read the table from.
super	A pointer to a super block from which to get the ID table location.
cmp	A compressor to use to extract compressed table blocks.

Returns

Zero on success, an SQFS_ERROR on failure.

sqfs_id_table_write()

SQFS_API int sqfs_id_table_write	(	sqfs_id_table_t *	tbl,
		sqfs_file_t *	file,
		sqfs_super_t *	super,
		sqfs_compressor_t *	cmp
	)

Write an ID table to disk.

Parameters

tbl	A pointer to an ID table object.
file	The underlying file to append the table to.
super	A pointer to a super block in which to store the ID table start location.
cmp	A compressor to use to compress the ID table.

Returns

Zero on success, an SQFS_ERROR on failure.

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The documentation for this struct was generated from the following file:

• include/sqfs/id_table.h