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

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_deref, \
        const CxHashKey*: cx_hash_key_deref, \
        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 and dereferences CxHashKey pointers.

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_as_string()

cxstring cx_hash_key_as_string

(

const CxHashKey *

key

)

Interprets the key data as a string and returns it.

Parameters

key

the key

Returns

the key data as a string

cx_hash_key_bytes()

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

inlinestatic

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()

static CxHashKey cx_hash_key_cxstr ( cxstring str )

inlinestatic

Computes a hash key from a UCX string.

Parameters

str	the string

Returns

the hash key

cx_hash_key_deref()

static CxHashKey cx_hash_key_deref ( const CxHashKey * key )

inlinestatic

The dereference function for the CX_HASH_KEY() macro.

You should never need to use this manually.

Parameters

key	a pointer to a key

Returns

a copy of the key (not the data)

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 (not the data)

cx_hash_key_mutstr()

static CxHashKey cx_hash_key_mutstr ( cxmutstr str )

inlinestatic

Computes a hash key from a UCX string.

Parameters

str	the string

Returns

the hash key

cx_hash_key_str()

static CxHashKey cx_hash_key_str ( const char * str )

inlinestatic

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()

static CxHashKey cx_hash_key_u32 ( uint32_t x )

inlinestatic

Computes a hash key from a 32-bit integer.

Parameters

x	the integer

Returns

the hash key

cx_hash_key_u64()

static CxHashKey cx_hash_key_u64 ( uint64_t x )

inlinestatic

Computes a hash key from a 64-bit integer.

Parameters

x	the integer

Returns

the hash key

cx_hash_key_ustr()

static CxHashKey cx_hash_key_ustr ( const unsigned char * str )

inlinestatic

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()

static uint32_t cx_hash_u32 ( uint32_t x )

inlinestatic

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()

static uint64_t cx_hash_u64 ( uint64_t x )

inlinestatic

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