test_dsm_registry.c

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/*--------------------------------------------------------------------------
 *
 * test_dsm_registry.c
 *    Test the dynamic shared memory registry.
 *
 * Copyright (c) 2024-2025, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *      src/test/modules/test_dsm_registry/test_dsm_registry.c
 *
 * -------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "fmgr.h"
#include "storage/dsm_registry.h"
#include "storage/lwlock.h"
#include "utils/builtins.h"
 
PG_MODULE_MAGIC;
 
typedef struct TestDSMRegistryStruct
{
    int         val;
    LWLock      lck;
} TestDSMRegistryStruct;
 
typedef struct TestDSMRegistryHashEntry
{
    char        key[64];
    dsa_pointer val;
} TestDSMRegistryHashEntry;
 
static TestDSMRegistryStruct *tdr_dsm;
static dsa_area *tdr_dsa;
static dshash_table *tdr_hash;
 
static const dshash_parameters dsh_params = {
    offsetof(TestDSMRegistryHashEntry, val),
    sizeof(TestDSMRegistryHashEntry),
    dshash_strcmp,
    dshash_strhash,
    dshash_strcpy
};
 
static void
init_tdr_dsm(void *ptr)
{
    TestDSMRegistryStruct *dsm = (TestDSMRegistryStruct *) ptr;
 
    LWLockInitialize(&dsm->lck, LWLockNewTrancheId("test_dsm_registry"));
    dsm->val = 0;
}
 
static void
tdr_attach_shmem(void)
{
    bool        found;
 
    tdr_dsm = GetNamedDSMSegment("test_dsm_registry_dsm",
                                 sizeof(TestDSMRegistryStruct),
                                 init_tdr_dsm,
                                 &found);
 
    if (tdr_dsa == NULL)
        tdr_dsa = GetNamedDSA("test_dsm_registry_dsa", &found);
 
    if (tdr_hash == NULL)
        tdr_hash = GetNamedDSHash("test_dsm_registry_hash", &dsh_params, &found);
}
 
PG_FUNCTION_INFO_V1(set_val_in_shmem);
Datum
set_val_in_shmem(PG_FUNCTION_ARGS)
{
    tdr_attach_shmem();
 
    LWLockAcquire(&tdr_dsm->lck, LW_EXCLUSIVE);
    tdr_dsm->val = PG_GETARG_INT32(0);
    LWLockRelease(&tdr_dsm->lck);
 
    PG_RETURN_VOID();
}
 
PG_FUNCTION_INFO_V1(get_val_in_shmem);
Datum
get_val_in_shmem(PG_FUNCTION_ARGS)
{
    int         ret;
 
    tdr_attach_shmem();
 
    LWLockAcquire(&tdr_dsm->lck, LW_SHARED);
    ret = tdr_dsm->val;
    LWLockRelease(&tdr_dsm->lck);
 
    PG_RETURN_INT32(ret);
}
 
PG_FUNCTION_INFO_V1(set_val_in_hash);
Datum
set_val_in_hash(PG_FUNCTION_ARGS)
{
    TestDSMRegistryHashEntry *entry;
    char       *key = TextDatumGetCString(PG_GETARG_DATUM(0));
    char       *val = TextDatumGetCString(PG_GETARG_DATUM(1));
    bool        found;
 
    if (strlen(key) >= offsetof(TestDSMRegistryHashEntry, val))
        ereport(ERROR,
                (errmsg("key too long")));
 
    tdr_attach_shmem();
 
    entry = dshash_find_or_insert(tdr_hash, key, &found);
    if (found)
        dsa_free(tdr_dsa, entry->val);
 
    entry->val = dsa_allocate(tdr_dsa, strlen(val) + 1);
    strcpy(dsa_get_address(tdr_dsa, entry->val), val);
 
    dshash_release_lock(tdr_hash, entry);
 
    PG_RETURN_VOID();
}
 
PG_FUNCTION_INFO_V1(get_val_in_hash);
Datum
get_val_in_hash(PG_FUNCTION_ARGS)
{
    TestDSMRegistryHashEntry *entry;
    char       *key = TextDatumGetCString(PG_GETARG_DATUM(0));
    text       *val = NULL;
 
    tdr_attach_shmem();
 
    entry = dshash_find(tdr_hash, key, false);
    if (entry == NULL)
        PG_RETURN_NULL();
 
    val = cstring_to_text(dsa_get_address(tdr_dsa, entry->val));
 
    dshash_release_lock(tdr_hash, entry);
 
    PG_RETURN_TEXT_P(val);
}