hash_key.h File Reference

Interface for map implementations. More...

#include "common.h"
#include "string.h"

Go to the source code of this file.

Data Structures
struct	cx_hash_key_s
	Internal structure for a key within a hash map. More...

Macros
#define	CX_HASH_KEY(key)
	Creates a hash key from any of the supported types with implicit length.

Typedefs
typedef struct cx_hash_key_s	CxHashKey
	Type for a hash key.

Functions
void	cx_hash_murmur (CxHashKey *key)
	Computes a murmur2 32-bit hash.
uint32_t	cx_hash_u32 (uint32_t x)
	Mixes up a 32-bit integer to be used as a hash.
uint64_t	cx_hash_u64 (uint64_t x)
	Mixes up a 64-bit integer to be used as a hash.
CxHashKey	cx_hash_key_u32 (uint32_t x)
	Computes a hash key from a 32-bit integer.
CxHashKey	cx_hash_key_u64 (uint64_t x)
	Computes a hash key from a 64-bit integer.
CxHashKey	cx_hash_key_str (const char *str)
	Computes a hash key from a string.
CxHashKey	cx_hash_key_ustr (const unsigned char *str)
	Computes a hash key from a string.
CxHashKey	cx_hash_key_bytes (const unsigned char *bytes, size_t len)
	Computes a hash key from a byte array.
CxHashKey	cx_hash_key (const void *obj, size_t len)
	Computes a hash key for an arbitrary object.
CxHashKey	cx_hash_key_cxstr (cxstring str)
	Computes a hash key from a UCX string.
CxHashKey	cx_hash_key_mutstr (cxmutstr str)
	Computes a hash key from a UCX string.
static CxHashKey	cx_hash_key_identity (CxHashKey key)
	The identity function for the CX_HASH_KEY() macro.
int	cx_hash_key_cmp (const void *left, const void *right)
	Compare function for hash keys.

Detailed Description

Interface for map implementations.

Author

Mike Becker

Olaf Wintermann

Copyright

2-Clause BSD License

Macro Definition Documentation

CX_HASH_KEY

#define CX_HASH_KEY

(

key

)

Value:

        _Generic((key), \
        CxHashKey: cx_hash_key_identity, \
        cxstring: cx_hash_key_cxstr, \
        cxmutstr: cx_hash_key_mutstr, \
        char*: cx_hash_key_str, \
        const char*: cx_hash_key_str, \
        unsigned char*: cx_hash_key_ustr, \
        const unsigned char*: cx_hash_key_ustr, \
        uint32_t: cx_hash_key_u32, \
        uint64_t: cx_hash_key_u64) \
        (key)

Creates a hash key from any of the supported types with implicit length.

Does nothing when passing a CxHashkey.

Supported types are UCX strings, zero-terminated C strings, and 32-bit or 64-bit unsigned integers.

Parameters

key	the key data

Returns

the CxHashKey

Function Documentation

cx_hash_key()

CxHashKey cx_hash_key	(	const void *	obj,
		size_t	len )

Computes a hash key for an arbitrary object.

The computation uses the in-memory representation that might not be the same on different platforms. Therefore, this hash should not be used for data exchange with different machines.

Parameters

obj	a pointer to an arbitrary object
len	the length of the object in memory

Returns

the hash key

cx_hash_key_bytes()

CxHashKey cx_hash_key_bytes	(	const unsigned char *	bytes,
		size_t	len )

Computes a hash key from a byte array.

Parameters

bytes	the array
len	the length

Returns

the hash key

cx_hash_key_cmp()

int cx_hash_key_cmp	(	const void *	left,
		const void *	right )

Compare function for hash keys.

The pointers are untyped to be compatible with the cx_compare_func signature.

Parameters

left	(CxHashKey*) the first key
right	(CxHashKey*) the second key

Returns

zero when the keys equal, non-zero when they differ

cx_hash_key_cxstr()

CxHashKey cx_hash_key_cxstr

(

cxstring

str

)

Computes a hash key from a UCX string.

Parameters

str	the string

Returns

the hash key

cx_hash_key_identity()

static CxHashKey cx_hash_key_identity ( CxHashKey key )

inlinestatic

The identity function for the CX_HASH_KEY() macro.

You should never need to use this manually.

Parameters

key

the key

Returns

a copy of the key

cx_hash_key_mutstr()

CxHashKey cx_hash_key_mutstr

(

cxmutstr

str

)

Computes a hash key from a UCX string.

Parameters

str	the string

Returns

the hash key

cx_hash_key_str()

CxHashKey cx_hash_key_str

(

const char *

str

)

Computes a hash key from a string.

The string needs to be zero-terminated.

Parameters

str	the string

Returns

the hash key

cx_hash_key_u32()

CxHashKey cx_hash_key_u32

(

uint32_t

x

)

Computes a hash key from a 32-bit integer.

Parameters

x	the integer

Returns

the hash key

cx_hash_key_u64()

CxHashKey cx_hash_key_u64

(

uint64_t

x

)

Computes a hash key from a 64-bit integer.

Parameters

x	the integer

Returns

the hash key

cx_hash_key_ustr()

CxHashKey cx_hash_key_ustr

(

const unsigned char *

str

)

Computes a hash key from a string.

Use this function when the string is represented as an unsigned char array.

The string needs to be zero-terminated.

Parameters

str	the string

Returns

the hash key

cx_hash_murmur()

void cx_hash_murmur

(

CxHashKey *

key

)

Computes a murmur2 32-bit hash.

You need to initialize data and len in the key struct. The hash is then directly written to that struct.

Usually you should not need this function. Use cx_hash_key(), instead.

Note

If data is NULL, the hash is defined as 1574210520.

Parameters

key	the key, the hash shall be computed for

See also

cx_hash_key()

cx_hash_u32()

uint32_t cx_hash_u32

(

uint32_t

x

)

Mixes up a 32-bit integer to be used as a hash.

This function produces no collisions and has a good statistical distribution.

Parameters

x	the integer

Returns

the hash

cx_hash_u64()

uint64_t cx_hash_u64

(

uint64_t

x

)

Mixes up a 64-bit integer to be used as a hash.

This function produces no collisions and has a good statistical distribution.

Parameters

x	the integer

Returns

the hash