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Diffstat (limited to 'src/backend/nodes/extensible.c')
-rw-r--r-- | src/backend/nodes/extensible.c | 92 |
1 files changed, 92 insertions, 0 deletions
diff --git a/src/backend/nodes/extensible.c b/src/backend/nodes/extensible.c new file mode 100644 index 00000000000..8fb4767d4d2 --- /dev/null +++ b/src/backend/nodes/extensible.c @@ -0,0 +1,92 @@ +/*------------------------------------------------------------------------- + * + * extensible.c + * Support for extensible node types + * + * Loadable modules can define what are in effect new types of nodes using + * the routines in this file. All such nodes are flagged T_ExtensibleNode, + * with the extnodename field distinguishing the specific type. Use + * RegisterExtensibleNodeMethods to register a new type of extensible node, + * and GetExtensibleNodeMethods to get information about a previously + * registered type of extensible node. + * + * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group + * Portions Copyright (c) 1994, Regents of the University of California + * + * IDENTIFICATION + * src/backend/nodes/extensible.c + * + *------------------------------------------------------------------------- + */ +#include "postgres.h" + +#include "nodes/extensible.h" +#include "utils/hsearch.h" + +static HTAB *extensible_node_methods = NULL; + +typedef struct +{ + char extnodename[EXTNODENAME_MAX_LEN]; + const ExtensibleNodeMethods *methods; +} ExtensibleNodeEntry; + +/* + * Register a new type of extensible node. + */ +void +RegisterExtensibleNodeMethods(const ExtensibleNodeMethods *methods) +{ + ExtensibleNodeEntry *entry; + bool found; + + if (extensible_node_methods == NULL) + { + HASHCTL ctl; + + memset(&ctl, 0, sizeof(HASHCTL)); + ctl.keysize = NAMEDATALEN; + ctl.entrysize = sizeof(ExtensibleNodeEntry); + extensible_node_methods = hash_create("Extensible Node Methods", + 100, &ctl, HASH_ELEM); + } + + Assert(strlen(methods->extnodename) <= EXTNODENAME_MAX_LEN); + + entry = (ExtensibleNodeEntry *) hash_search(extensible_node_methods, + methods->extnodename, + HASH_ENTER, &found); + if (found) + ereport(ERROR, + (errcode(ERRCODE_DUPLICATE_OBJECT), + errmsg("extensible node type \"%s\" already exists", + methods->extnodename))); + + entry->methods = methods; +} + +/* + * Get the methods for a given type of extensible node. + */ +const ExtensibleNodeMethods * +GetExtensibleNodeMethods(const char *extnodename, bool missing_ok) +{ + ExtensibleNodeEntry *entry = NULL; + + if (extensible_node_methods != NULL) + entry = (ExtensibleNodeEntry *) hash_search(extensible_node_methods, + extnodename, + HASH_FIND, NULL); + + if (!entry) + { + if (missing_ok) + return NULL; + ereport(ERROR, + (errcode(ERRCODE_UNDEFINED_OBJECT), + errmsg("ExtensibleNodeMethods \"%s\" was not registered", + extnodename))); + } + + return entry->methods; +} |