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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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37
src/include/lib/dshash.h
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@@ -26,32 +26,13 @@ typedef dsa_pointer dshash_table_handle;
/* The type for hash values. */
typedef uint32 dshash_hash;
/*
* A function used for comparing keys. This version is compatible with
* HashCompareFunction in hsearch.h and memcmp.
*/
typedef int (*dshash_compare_function) (const void *a, const void *b, size_t size);
/* A function type for comparing keys. */
typedef int (*dshash_compare_function) (const void *a, const void *b,
size_t size, void *arg);
/*
* A function type used for comparing keys. This version allows compare
* functions to receive a pointer to arbitrary user data that was given to the
* create or attach function. Similar to qsort_arg_comparator.
*/
typedef int (*dshash_compare_arg_function) (const void *a, const void *b, void *arg);
/*
* A function type for computing hash values for keys. This version is
* compatible with HashValueFunc in hsearch.h and hash functions like
* tag_hash.
*/
typedef dshash_hash (*dshash_hash_function) (const void *v, size_t size);
/*
* A function type for computing hash values for keys. This version allows
* hash functions to receive a pointer to arbitrary user data that was given
* to the create or attach function.
*/
typedef dshash_hash (*dshash_hash_arg_function) (const void *v, void *arg);
/* A function type for computing hash values for keys. */
typedef dshash_hash (*dshash_hash_function) (const void *v, size_t size,
void *arg);
/*
* The set of parameters needed to create or attach to a hash table. The
@@ -70,9 +51,7 @@ typedef struct dshash_parameters
size_t key_size; /* Size of the key (initial bytes of entry) */
size_t entry_size; /* Total size of entry */
dshash_compare_function compare_function; /* Compare function */
dshash_compare_arg_function compare_arg_function; /* Arg version */
dshash_hash_function hash_function; /* Hash function */
dshash_hash_arg_function hash_arg_function; /* Arg version */
int tranche_id; /* The tranche ID to use for locks */
} dshash_parameters;
@@ -101,6 +80,10 @@ extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
extern void dshash_release_lock(dshash_table *hash_table, void *entry);
/* Convenience hash and compare functions wrapping memcmp and tag_hash. */
extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg);
extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg);
/* Debugging support. */
extern void dshash_dump(dshash_table *hash_table);