Hashtable - String/Index

Typedefs
typedef struct M_hash_stridx	M_hash_stridx_t
typedef struct M_hash_stridx_enum	M_hash_stridx_enum_t

Enumerations
enum	M_hash_stridx_flags_t {   M_HASH_STRIDX_NONE = 0 ,   M_HASH_STRIDX_CASECMP = 1 << 0 ,   M_HASH_STRIDX_KEYS_UPPER = 1 << 1 ,   M_HASH_STRIDX_KEYS_LOWER = 1 << 2 ,   M_HASH_STRIDX_KEYS_ORDERED = 1 << 3 ,   M_HASH_STRIDX_KEYS_SORTASC = 1 << 4 ,   M_HASH_STRIDX_KEYS_SORTDESC = 1 << 5 ,   M_HASH_STRIDX_MULTI_VALUE = 1 << 6 ,   M_HASH_STRIDX_MULTI_GETLAST = 1 << 7 ,   M_HASH_STRIDX_STATIC_SEED = 1 << 8 }

Functions
M_hash_stridx_t *	M_hash_stridx_create (size_t size, M_uint8 fillpct, M_uint32 flags) M_MALLOC
void	M_hash_stridx_destroy (M_hash_stridx_t *h) M_FREE(1)
M_bool	M_hash_stridx_insert (M_hash_stridx_t *h, const char *key, size_t value)
M_bool	M_hash_stridx_remove (M_hash_stridx_t *h, const char *key)
M_bool	M_hash_stridx_get (const M_hash_stridx_t *h, const char *key, size_t *value)
size_t	M_hash_stridx_get_direct (const M_hash_stridx_t *h, const char *key)
M_bool	M_hash_stridx_is_multi (const M_hash_stridx_t *h)
M_bool	M_hash_stridx_multi_len (const M_hash_stridx_t *h, const char *key, size_t *len)
M_bool	M_hash_stridx_multi_get (const M_hash_stridx_t *h, const char *key, size_t idx, size_t *value)
size_t	M_hash_stridx_multi_get_direct (const M_hash_stridx_t *h, const char *key, size_t idx)
M_bool	M_hash_stridx_multi_remove (M_hash_stridx_t *h, const char *key, size_t idx)
M_uint32	M_hash_stridx_size (const M_hash_stridx_t *h)
size_t	M_hash_stridx_num_collisions (const M_hash_stridx_t *h)
size_t	M_hash_stridx_num_expansions (const M_hash_stridx_t *h)
size_t	M_hash_stridx_num_keys (const M_hash_stridx_t *h)
size_t	M_hash_stridx_enumerate (const M_hash_stridx_t *h, M_hash_stridx_enum_t **hashenum)
M_bool	M_hash_stridx_enumerate_next (const M_hash_stridx_t *h, M_hash_stridx_enum_t *hashenum, const char **key, size_t *value)
void	M_hash_stridx_enumerate_free (M_hash_stridx_enum_t *hashenum)
void	M_hash_stridx_merge (M_hash_stridx_t **dest, M_hash_stridx_t *src) M_FREE(2)
M_hash_stridx_t *	M_hash_stridx_duplicate (const M_hash_stridx_t *h) M_MALLOC

Detailed Description

Hashtable, meant for storing string keys and index values. This is primarily used for something like dereferencing a CSV column name to its position.

References to the data will always be read-only. All keys and values will be duplicated by the hashtable.

Typedef Documentation

M_hash_stridx_t

typedef struct M_hash_stridx M_hash_stridx_t

M_hash_stridx_enum_t

typedef struct M_hash_stridx_enum M_hash_stridx_enum_t

Enumeration Type Documentation

M_hash_stridx_flags_t

enum M_hash_stridx_flags_t

Flags for controlling the behavior of the hashtable.

Enumerator
M_HASH_STRIDX_NONE	Case sensitive single value (new values replace).
M_HASH_STRIDX_CASECMP	Key compare is case insensitive.
M_HASH_STRIDX_KEYS_UPPER	Keys will be upper cased before being inserted. Should be used in conjunction with M_HASH_STRIDX_CASECMP.
M_HASH_STRIDX_KEYS_LOWER	Keys will be lower cased before being inserted. Should be used in conjunction with M_HASH_STRIDX_CASECMP.
M_HASH_STRIDX_KEYS_ORDERED	Keys should be ordered. Default is insertion order unless the sorted option is specified.
M_HASH_STRIDX_KEYS_SORTASC	When the keys are ordered sort them using the key_equality function.
M_HASH_STRIDX_KEYS_SORTDESC	When the keys are ordered sort them using the key_equality function.
M_HASH_STRIDX_MULTI_VALUE	Allow keys to contain multiple values. Sorted in insertion order another sorting is specified.
M_HASH_STRIDX_MULTI_GETLAST	When using get and get_direct function get the last value from the list when allowing multiple values. The default is to get the first value.
M_HASH_STRIDX_STATIC_SEED	Use a static seed for hash function initialization. This greatly reduces the security of the hashtable and removes collision attack protections. This should only be used as a performance optimization when creating millions of hashtables with static data specifically for quick look up. DO NOT use this flag with any hashtable that could store user generated data! Be very careful about duplicating a hashtable that was created with this flag. All duplicates will use the static seed.

Function Documentation

M_hash_stridx_create()

M_hash_stridx_t * M_hash_stridx_create	(	size_t	size,
		M_uint8	fillpct,
		M_uint32	flags
	)

Create a new hashtable.

The hashtable will pre-allocate an array of buckets based on the rounded up size specified. Any hash collisions will result in those collisions being chained together via a linked list. The hashtable will auto-expand by a power of 2 when the fill percentage specified is reached. All key entries are compared in a case-insensitive fashion, and are duplicated internally. Values are duplicated. Case is preserved for both keys and values.

Parameters

[in]	size	Size of the hash table. If not specified as a power of 2, will be rounded up to the nearest power of 2.
[in]	fillpct	The maximum fill percentage before the hash table is expanded. If 0 is specified, the hashtable will never expand, otherwise the value must be between 1 and 99 (recommended: 75).
[in]	flags	M_hash_stridx_flags_t flags for modifying behavior.

Returns

Allocated hashtable.

See also

M_hash_stridx_destroy

M_hash_stridx_destroy()

void M_hash_stridx_destroy

(

M_hash_stridx_t *

h

)

Destroy the hashtable.

Parameters

[in]

h

Hashtable to destroy

M_hash_stridx_insert()

M_bool M_hash_stridx_insert	(	M_hash_stridx_t *	h,
		const char *	key,
		size_t	value
	)

Insert an entry into the hashtable.

Parameters

[in,out]	h	Hashtable being referenced.
[in]	key	Key to insert. A NULL or empty string is explicity disallowed.
[in]	value	Value to insert into hashtable.

Returns

M_TRUE on success, or M_FALSE on failure.

M_hash_stridx_remove()

M_bool M_hash_stridx_remove	(	M_hash_stridx_t *	h,
		const char *	key
	)

Remove an entry from the hashtable.

Parameters

[in,out]	h	Hashtable being referenced.
[in]	key	Key to remove from the hashtable. A NULL or empty string is explicitly disallowed.

Returns

M_TRUE on success, or M_FALSE if key does not exist.

M_hash_stridx_get()

M_bool M_hash_stridx_get	(	const M_hash_stridx_t *	h,
		const char *	key,
		size_t *	value
	)

Retrieve the value for a key from the hashtable.

Parameters

[in]	h	Hashtable being referenced.
[in]	key	Key for value. A NULL or empty string is explicitly disallowed.
[out]	value	Pointer to value stored in the hashtable. Optional, pass NULL if not needed.

Returns

M_TRUE if value retrieved, M_FALSE if key does not exist.

M_hash_stridx_get_direct()

size_t M_hash_stridx_get_direct	(	const M_hash_stridx_t *	h,
		const char *	key
	)

Retrieve the value for a key from the hashtable, and return it directly as the return value.

This cannot be used if you need to differentiate between a key that doesn't exist vs a key with a 0 value.

Parameters

[in]	h	Hashtable being referenced.
[in]	key	Key for value to retrieve from the hashtable. A NULL or empty string is explicitly disallowed.

Returns

NULL if key doesn't exist or NULL value on file, otherwise the value.

M_hash_stridx_is_multi()

M_bool M_hash_stridx_is_multi

(

const M_hash_stridx_t *

h

)

Wether the hashtable a multi value table.

Parameters

[in]

h

Hashtable being referenced.

Returns

M_TRUE if a multi value hashtable.

M_hash_stridx_multi_len()

M_bool M_hash_stridx_multi_len	(	const M_hash_stridx_t *	h,
		const char *	key,
		size_t *	len
	)

Get the number of values for a given key.

Parameters

[in]	h	Hashtable being referenced.
[in]	key	Key for value to retrieve.
[out]	len	The number of values.

Returns

M_TRUE if length is retrieved, M_FALSE if key does not exist.

M_hash_stridx_multi_get()

M_bool M_hash_stridx_multi_get	(	const M_hash_stridx_t *	h,
		const char *	key,
		size_t	idx,
		size_t *	value
	)

Retrieve the value for a key from the given index when supporting muli-values.

Parameters

[in]	h	Hashtable being referenced.
[in]	key	Key for value to retrieve.
[in]	idx	The index the value resides at.
[out]	value	Pointer to value stored. Optional, pass NULL if not needed.

Returns

M_TRUE if value retrieved, M_FALSE if key does not exist

M_hash_stridx_multi_get_direct()

size_t M_hash_stridx_multi_get_direct	(	const M_hash_stridx_t *	h,
		const char *	key,
		size_t	idx
	)

Retrieve the value for a key from the given index when supporting muli-values.

Parameters

[in]	h	Hashtable being referenced.
[in]	key	Key for value to retrieve.
[in]	idx	The index the value resides at.

Returns

M_TRUE if value retrieved, M_FALSE if key does not exist.

M_hash_stridx_multi_remove()

M_bool M_hash_stridx_multi_remove	(	M_hash_stridx_t *	h,
		const char *	key,
		size_t	idx
	)

Remove a value from the hashtable when supporting muli-values.

If all values have been removed then the key will be removed.

Parameters

[in,out]	h	Hashtable being referenced
[in]	key	Key for value to retrieve.
[in]	idx	The index the value resides at.

Returns

M_TRUE if the value was removed, M_FALSE if key does not exist.

M_hash_stridx_size()

M_uint32 M_hash_stridx_size

(

const M_hash_stridx_t *

h

)

Retrieve the current size (number of buckets/slots, not necessarily used).

Parameters

[in]

h

Hashtable being referenced.

Returns

Size of the hashtable

M_hash_stridx_num_collisions()

size_t M_hash_stridx_num_collisions

(

const M_hash_stridx_t *

h

)

Retrieve the number of collisions for hashtable entries that has occurred since creation.

Parameters

[in]

h

Hashtable being referenced.

Returns

Number of collisions.

M_hash_stridx_num_expansions()

size_t M_hash_stridx_num_expansions

(

const M_hash_stridx_t *

h

)

Retrieve the number of expansions/rehashes since creation.

Parameters

[in]

h

Hashtable being referenced.

Returns

number of expansions/rehashes.

M_hash_stridx_num_keys()

size_t M_hash_stridx_num_keys

(

const M_hash_stridx_t *

h

)

Retrieve the number of entries in the hashtable.

This is the number of keys stored.

Parameters

[in]

h

Hashtable being referenced.

Returns

number of entries in the hashtable.

M_hash_stridx_enumerate()

size_t M_hash_stridx_enumerate	(	const M_hash_stridx_t *	h,
		M_hash_stridx_enum_t **	hashenum
	)

Start an enumeration of the keys within a hashtable.

Parameters

[in]	h	Hashtable being referenced.
[out]	hashenum	Outputs an initialized state variable for starting an enumeration.

Returns

Number of items in the hashtable

See also

M_hash_stridx_enumerate_free

M_hash_stridx_enumerate_next()

M_bool M_hash_stridx_enumerate_next	(	const M_hash_stridx_t *	h,
		M_hash_stridx_enum_t *	hashenum,
		const char **	key,
		size_t *	value
	)

Retrieve the next item from a hashtable enumeration.

If multi-value, keys will appear multiple times as each value will be retrieved individually.

Parameters

[in]	h	Hashtable being referenced.
[in,out]	hashenum	State variable for tracking the enumeration process.
[out]	key	Value of next enumerated key. Optional, pass NULL if not needed.
[out]	value	Value of next enumerated value. Optional, pass NULL if not needed.

Returns

M_TRUE if enumeration succeeded, M_FALSE if no more keys.

M_hash_stridx_enumerate_free()

void M_hash_stridx_enumerate_free

(

M_hash_stridx_enum_t *

hashenum

)

Destroy an enumeration state.

Parameters

[in]

hashenum

Enumeration to destroy.

M_hash_stridx_merge()

void M_hash_stridx_merge	(	M_hash_stridx_t **	dest,
		M_hash_stridx_t *	src
	)

Merge two hashtables together.

The second (src) hashtable will be destroyed automatically upon completion of this function. Any key/value pointers for the hashtable will be directly copied over to the destination hashtable, they will not be duplicated. Any keys which exist in 'dest' that also exist in 'src' will be overwritten by the 'src' value.

If dest and src are multi-value, all values from src will be copied into dest and the values from dest will not be removed. If dest is not multi-value and src is, then only the last value in src will be present in dest. If dest is multi-value and src is not, then the value from src will be added to dest.

Parameters

[in,out]	dest	Pointer by reference to the hashtable receiving the key/value pairs. if dest is NULL, the src address will simply be copied to dest.
[in,out]	src	Pointer to the hashtable giving up its key/value pairs.

M_hash_stridx_duplicate()

M_hash_stridx_t * M_hash_stridx_duplicate

(

const M_hash_stridx_t *

h

)

Duplicate an existing hashtable.

Copying all keys and values.

Parameters

[in]

h

Hashtable to be copied.

Returns

Duplicated hashtable.