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Consolidate the function pointer types used by dshash.c.

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Commit 8c0d7bafad introduced dshash with hash
and compare functions like DynaHash's, and also variants that take a user
data pointer instead of size.  Simplify the interface by merging them into
a single pair of function pointer types that take both size and a user data
pointer.

Since it is anticipated that memcmp and tag_hash behavior will be a common
requirement, provide wrapper functions dshash_memcmp and dshash_memhash that
conform to the new function types.

Author: Thomas Munro
Reviewed-By: Andres Freund
Discussion: https://postgr.es/m/20170823054644.efuzftxjpfi6wwqs%40alap3.anarazel.de
This commit is contained in:
Andres Freund
2017-08-24 17:01:36 -07:00
parent 4569715bd6
commit d7694fc148
2 changed files with 39 additions and 63 deletions
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65
src/backend/lib/dshash.c
View File

@ -35,6 +35,7 @@
#include "storage/ipc.h"
#include "storage/lwlock.h"
#include "utils/dsa.h"
#include "utils/hsearch.h"
#include "utils/memutils.h"
/*
@ -188,9 +189,8 @@ static inline bool equal_keys(dshash_table *hash_table,
/*
* Create a new hash table backed by the given dynamic shared area, with the
* given parameters. The returned object is allocated in backend-local memory
* using the current MemoryContext. If 'arg' is non-null, the arg variants of
* hash and compare functions must be provided in 'params' and 'arg' will be
* passed down to them.
* using the current MemoryContext. 'arg' will be passed through to the
* compare and hash functions.
*/
dshash_table *
dshash_create(dsa_area *area, const dshash_parameters *params, void *arg)
@ -198,14 +198,6 @@ dshash_create(dsa_area *area, const dshash_parameters *params, void *arg)
dshash_table *hash_table;
dsa_pointer control;
/* Sanity checks on the set of supplied functions. */
Assert((params->compare_function != NULL) ^
(params->compare_arg_function != NULL));
Assert((params->hash_function != NULL) ^
(params->hash_arg_function != NULL));
Assert(arg == NULL || (params->compare_arg_function != NULL));
Assert(arg == NULL || (params->hash_arg_function != NULL));
/* Allocate the backend-local object representing the hash table. */
hash_table = palloc(sizeof(dshash_table));
@ -263,9 +255,8 @@ dshash_create(dsa_area *area, const dshash_parameters *params, void *arg)
/*
* Attach to an existing hash table using a handle. The returned object is
* allocated in backend-local memory using the current MemoryContext. If
* 'arg' is non-null, the arg variants of hash and compare functions must be
* provided in 'params' and 'arg' will be passed down to them.
* allocated in backend-local memory using the current MemoryContext. 'arg'
* will be passed through to the compare and hash functions.
*/
dshash_table *
dshash_attach(dsa_area *area, const dshash_parameters *params,
@ -274,14 +265,6 @@ dshash_attach(dsa_area *area, const dshash_parameters *params,
dshash_table *hash_table;
dsa_pointer control;
/* Sanity checks on the set of supplied functions. */
Assert((params->compare_function != NULL) ^
(params->compare_arg_function != NULL));
Assert((params->hash_function != NULL) ^
(params->hash_arg_function != NULL));
Assert(arg == NULL || (params->compare_arg_function != NULL));
Assert(arg == NULL || (params->hash_arg_function != NULL));
/* Allocate the backend-local object representing the hash table. */
hash_table = palloc(sizeof(dshash_table));
@ -582,6 +565,24 @@ dshash_release_lock(dshash_table *hash_table, void *entry)
LWLockRelease(PARTITION_LOCK(hash_table, partition_index));
}
/*
* A compare function that forwards to memcmp.
*/
int
dshash_memcmp(const void *a, const void *b, size_t size, void *arg)
{
return memcmp(a, b, size);
}
/*
* A hash function that forwards to tag_hash.
*/
dshash_hash
dshash_memhash(const void *v, size_t size, void *arg)
{
return tag_hash(v, size);
}
/*
* Print debugging information about the internal state of the hash table to
* stderr. The caller must hold no partition locks.
@ -874,11 +875,9 @@ delete_item_from_bucket(dshash_table *hash_table,
static inline dshash_hash
hash_key(dshash_table *hash_table, const void *key)
{
if (hash_table->params.hash_arg_function != NULL)
return hash_table->params.hash_arg_function(key, hash_table->arg);
else
return hash_table->params.hash_function(key,
hash_table->params.key_size);
return hash_table->params.hash_function(key,
hash_table->params.key_size,
hash_table->arg);
}
/*
@ -887,13 +886,7 @@ hash_key(dshash_table *hash_table, const void *key)
static inline bool
equal_keys(dshash_table *hash_table, const void *a, const void *b)
{
int r;
if (hash_table->params.compare_arg_function != NULL)
r = hash_table->params.compare_arg_function(a, b, hash_table->arg);
else
r = hash_table->params.compare_function(a, b,
hash_table->params.key_size);
return r == 0;
return hash_table->params.compare_function(a, b,
hash_table->params.key_size,
hash_table->arg) == 0;
}