pg_parse 0.14.0

PostgreSQL parser that uses the actual PostgreSQL server source to parse SQL queries and return the internal PostgreSQL parse tree.
Documentation 
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/*
 * libpg_query version of get_func_arg_info that pulls argument info from the
 * libpg_query-forged pg_proc tuple via the SysCacheGetAttr mock. The body
 * matches upstream's funcapi.c logic; only the surrounding context (tuple
 * source) differs.
 */
int
get_func_arg_info(HeapTuple procTup,
				  Oid **p_argtypes, char ***p_argnames, char **p_argmodes)
{
	Form_pg_proc procStruct = (Form_pg_proc) GETSTRUCT(procTup);
	Datum		proallargtypes;
	Datum		proargmodes;
	Datum		proargnames;
	bool		isNull;
	ArrayType  *arr;
	int			numargs;
	Datum	   *elems;
	int			nelems;
	int			i;

	proallargtypes = SysCacheGetAttr(PROCOID, procTup,
									 Anum_pg_proc_proallargtypes,
									 &isNull);
	if (!isNull)
	{
		arr = DatumGetArrayTypeP(proallargtypes);
		numargs = ARR_DIMS(arr)[0];
		if (ARR_NDIM(arr) != 1 ||
			numargs < 0 ||
			ARR_HASNULL(arr) ||
			ARR_ELEMTYPE(arr) != OIDOID)
			elog(ERROR, "proallargtypes is not a 1-D Oid array or it contains nulls");
		*p_argtypes = (Oid *) palloc(numargs * sizeof(Oid));
		memcpy(*p_argtypes, ARR_DATA_PTR(arr),
			   numargs * sizeof(Oid));
	}
	else
	{
		numargs = procStruct->proargtypes.dim1;
		*p_argtypes = (Oid *) palloc(numargs * sizeof(Oid));
		memcpy(*p_argtypes, procStruct->proargtypes.values,
			   numargs * sizeof(Oid));
	}

	proargnames = SysCacheGetAttr(PROCOID, procTup,
								  Anum_pg_proc_proargnames,
								  &isNull);
	if (isNull)
		*p_argnames = NULL;
	else
	{
		deconstruct_array_builtin(DatumGetArrayTypeP(proargnames), TEXTOID,
								  &elems, NULL, &nelems);
		if (nelems != numargs)
			elog(ERROR, "proargnames must have the same number of elements as the function has arguments");
		*p_argnames = (char **) palloc(sizeof(char *) * numargs);
		for (i = 0; i < numargs; i++)
			(*p_argnames)[i] = TextDatumGetCString(elems[i]);
	}

	proargmodes = SysCacheGetAttr(PROCOID, procTup,
								  Anum_pg_proc_proargmodes,
								  &isNull);
	if (isNull)
		*p_argmodes = NULL;
	else
	{
		arr = DatumGetArrayTypeP(proargmodes);
		if (ARR_NDIM(arr) != 1 ||
			ARR_DIMS(arr)[0] != numargs ||
			ARR_HASNULL(arr) ||
			ARR_ELEMTYPE(arr) != CHAROID)
			elog(ERROR, "proargmodes is not a 1-D char array of length %d or it contains nulls",
				 numargs);
		*p_argmodes = (char *) palloc(numargs * sizeof(char));
		memcpy(*p_argmodes, ARR_DATA_PTR(arr),
			   numargs * sizeof(char));
	}

	return numargs;
}