The Configuration Group contains the API the gets/sets the underlying configuration of an MDBM. More...

Classes
struct	mdbm_shake_data_v3

Macros
#define	MDBM_ALIGN_8_BITS 0x0
	1-Byte data alignment More...

#define	MDBM_ALIGN_16_BITS 0x1
	2-Byte data alignment More...

#define	MDBM_ALIGN_32_BITS 0x3
	4-Byte data alignment More...

#define	MDBM_ALIGN_64_BITS 0x7
	8-Byte data alignment More...

#define	_MDBM_MAGIC 0x01023962
	V2 file identifier. More...

#define	_MDBM_MAGIC_NEW 0x01023963
	V2 file identifier with large objects. More...

#define	_MDBM_MAGIC_NEW2 0x01023964
	V3 file identifier. More...

#define	MDBM_MAGIC _MDBM_MAGIC_NEW2

Typedefs
typedef int(*	mdbm_shake_func_v3 )(MDBM , const datum , const datum , struct mdbm_shake_data_v3 )

Functions
void	mdbm_stat_header (MDBM *db)
	Prints to stdout various pieces of information, specifically: page size, page count, hash function, running with or without locking. More...

int	mdbm_get_hash (MDBM *db)
	Gets the MDBM's hash function identifier. More...

int	mdbm_sethash (MDBM *db, int hashid)
	Sets the hashing function for a given MDBM. More...

int	mdbm_setspillsize (MDBM *db, int size)
	Sets the size of item data value which will be put on the large-object heap rather than inline. More...

int	mdbm_get_alignment (MDBM *db)
	Gets the MDBM's record byte-alignment. More...

int	mdbm_set_alignment (MDBM *db, int align)
	Sets a database's byte-size alignment for keys and values within a page. More...

uint64_t	mdbm_get_limit_size (MDBM *db)
	Gets the MDBM's size limit. More...

int	mdbm_limit_size_v3 (MDBM db, mdbm_ubig_t max_page, mdbm_shake_func_v3 shake, void user)
	Limits the size of a V3 database to a maximum number of pages. More...

int	mdbm_limit_dir_size (MDBM *db, int pages)
	Limits the internal page directory size to a number of pages. More...

uint32_t	mdbm_get_version (MDBM *db)
	Gets the on-disk format version number of an MDBM. More...

uint64_t	mdbm_get_size (MDBM *db)
	Gets the current MDBM's size. More...

int	mdbm_get_page_size (MDBM *db)
	Get the MDBM's page size. More...

int	mdbm_get_magic_number (MDBM db, uint32_t magic)
	Gets the magic number from an MDBM. More...

int	mdbm_set_window_size (MDBM *db, size_t wsize)
	Sets the window size for an MDBM. More...

Detailed Description

The Configuration Group contains the API the gets/sets the underlying configuration of an MDBM.

Most of the commands that set the configuration must be done at MDBM-creation time.

Macro Definition Documentation

#define MDBM_ALIGN_8_BITS 0x0

1-Byte data alignment

#define MDBM_ALIGN_16_BITS 0x1

2-Byte data alignment

#define MDBM_ALIGN_32_BITS 0x3

4-Byte data alignment

#define MDBM_ALIGN_64_BITS 0x7

8-Byte data alignment

#define _MDBM_MAGIC 0x01023962

V2 file identifier.

#define _MDBM_MAGIC_NEW 0x01023963

V2 file identifier with large objects.

#define _MDBM_MAGIC_NEW2 0x01023964

V3 file identifier.

#define MDBM_MAGIC _MDBM_MAGIC_NEW2

Typedef Documentation

typedef int(* mdbm_shake_func_v3)(MDBM *, const datum *, const datum *, struct mdbm_shake_data_v3 *)

Function Documentation

void mdbm_stat_header ( MDBM * db )

Prints to stdout various pieces of information, specifically: page size, page count, hash function, running with or without locking.

NOTE: There is only a V2 implementation. V3 not currently supported.

Parameters

[in,out] db Database handle

int mdbm_get_hash ( MDBM * db )

Gets the MDBM's hash function identifier.

Parameters

[in,out] db Database handle

Returns: Hash function identifier

Return values

MDBM_HASH_CRC32	- Table based 32bit CRC
MDBM_HASH_EJB	- From hsearch
MDBM_HASH_PHONG	- Congruential hash
MDBM_HASH_OZ	- From sdbm
MDBM_HASH_TOREK	- From BerkeleyDB
MDBM_HASH_FNV	- Fowler/Vo/Noll hash (DEFAULT)
MDBM_HASH_STL	- STL string hash
MDBM_HASH_MD5	- MD5
MDBM_HASH_SHA_1	- SHA_1
MDBM_HASH_JENKINS	- Jenkins string
MDBM_HASH_HSIEH	- Hsieh SuperFast

int mdbm_sethash	(	MDBM *	db,
		int	hashid
	)

Sets the hashing function for a given MDBM.

The hash function must be set before storing anything to the db (this is not enforced, but entries stored before the hash change will become inaccessible if the hash function is changed).

NOTE: setting the hash must be be done at creation time, or when there is no data in an MDBM. Changing the hash function when there is existing data will result in not being able access that data in the future.

Parameters

[in,out]	db	Database handle
[in]	hashid	Numeric identifier for new hash function.

Returns: Set hash status

Return values

0	Error, invalid hashid
1	Success

Available Hash IDs are:

MDBM_HASH_CRC32 - Table based 32bit CRC
MDBM_HASH_EJB - From hsearch
MDBM_HASH_PHONG - Congruential hash
MDBM_HASH_OZ - From sdbm
MDBM_HASH_TOREK - From BerkeleyDB
MDBM_HASH_FNV - Fowler/Vo/Noll hash (DEFAULT)
MDBM_HASH_STL - STL string hash
MDBM_HASH_MD5 - MD5
MDBM_HASH_SHA_1 - SHA_1
MDBM_HASH_JENKINS - Jenkins string
MDBM_HASH_HSIEH - Hsieh SuperFast

int mdbm_setspillsize	(	MDBM *	db,
		int	size
	)

Sets the size of item data value which will be put on the large-object heap rather than inline.

The spill size can be changed at any point after the db has been created. However, it's a recommended practice to set the spill size at creation time.

NOTE: The database has to be opened with the MDBM_LARGE_OBJECTS flag for spillsize to take effect.

Parameters

[in,out]	db	Database handle
[in]	size	New large-object threshold size

Returns: Set spill size status

Return values

-1	Error, and errno is set
0	Success

int mdbm_get_alignment ( MDBM * db )

Gets the MDBM's record byte-alignment.

Parameters

[in,out] db Database handle

Returns: Alignment mask.

Return values

0	- 8-bit alignment
1	- 16-bit alignment
3	- 32-bit alignment
7	- 64-bit alignment

int mdbm_set_alignment	(	MDBM *	db,
		int	align
	)

Sets a database's byte-size alignment for keys and values within a page.

This feature is useful for hardware/memory architectures that incur a performance penalty for unaligned accesses. Later (2006+) i386 and x86 architectures do not need special byte alignment, and should use the default of 8-bit alignment.

NOTE: setting the byte alignment must be be done at MDBM-creation time, or when there is no data in an MDBM. Changing the byte alignment when there is existing data will result in in undefined behavior and probably a crash.

Parameters

[in,out]	db	Database handle
[in]	align	Alignment mask

Returns: Alignment status

Return values

-1	Error, and errno is set
0	Success

uint64_t mdbm_get_limit_size ( MDBM * db )

Gets the MDBM's size limit.

Returns the limit set for the size of the db using the mdbm_limit_size_v3 routine.

Parameters

[in,out] db Database handle

Returns: database size limit

Return values

0	No limit is set
Total	number of bytes for maximum database size, including header and directory

int mdbm_limit_size_v3	(	MDBM *	db,
		mdbm_ubig_t	max_page,
		mdbm_shake_func_v3	shake,
		void *	user
	)

Limits the size of a V3 database to a maximum number of pages.

This function causes the MDBM to shake whenever a full page would cause the db to grow beyond the specified max number of pages. The limit size for an MDBM may be increased over time, but is may never be decreased.

Parameters

[in,out]	db	Database handle
[in]	max_page	Maximum number of data pages
[in]	shake	Shake function.
[in]	user	Pointer to user data that will be passed to the shake function

Returns: Limit size status

Return values

-1	Error, and errno is set
0	Success

int mdbm_limit_dir_size	(	MDBM *	db,
		int	pages
	)

Limits the internal page directory size to a number of pages.

The number of pages is rounded up to a power of 2.

Parameters

[in,out]	db	Database handle
[in]	pages	Number of data pages

Returns: Limit dir size status

Return values

-1	Error, and errno is set
0	Success

uint32_t mdbm_get_version ( MDBM * db )

Gets the on-disk format version number of an MDBM.

Parameters

[in,out] db Database handle

Returns: On-disk file format version number

Return values

2	- MDBM V2
3	- MDBM V3

uint64_t mdbm_get_size ( MDBM * db )

Gets the current MDBM's size.

Parameters

[in,out] db Database handle

Returns: Size of database in bytes.

int mdbm_get_page_size ( MDBM * db )

Get the MDBM's page size.

Parameters

[in,out] db Database handle

Returns: Number of bytes in a database page

int mdbm_get_magic_number	(	MDBM *	db,
		uint32_t *	magic
	)

Gets the magic number from an MDBM.

Parameters

[in,out]	db	Database handle
[out]	magic	MDBM magic number (internal version identifier)

Returns: Magic number status

Return values

-3	Cannot read all of the magic number
-2	File is truncated (empty)
-1	Cannot read file
0	Magic number returned in magic

int mdbm_set_window_size	(	MDBM *	db,
		size_t	wsize
	)

Sets the window size for an MDBM.

Windowing is typically used for a very large data store where only part of it will be mapped to memory. In windowing mode, pages are accessed through a "window" to the database.

In order to use windowing mode, the page size must be a multiple of the system page size (4K on most systems). The system page size can be retrieved by calling getpagesize or sysconf(_SC_PAGESIZE).

NOTE: It is best if the minimum window size chosen is: (4*max-large-object-size + n*8*pagesize)

NOTE: API exists in MDBM V3 only, and using mdbm_set_window_size requires opening MDBM with MDBM_O_RDWR.

Parameters

[in,out]	db	Database handle for windowed access, typically a backing store database
[in]	wsize	Window size which must be at least 4X the page size used for the database. 0 means to remove windowing

Returns: Set window status

Return values

-1	Error, and errno is set
0	Success

Classes

Macros

Typedefs

Functions

Detailed Description

Macro Definition Documentation

Typedef Documentation

Function Documentation