Function PQsetvalue

src/interfaces/libpq/fe-exec.c:459–538

* Sets the value for a tuple field. The tup_num must be less than or * equal to PQntuples(res). If it is equal, a new tuple is created and * added to the result. * Returns a non-zero value for success and zero for failure. * (On failure, we report the specific problem via pqInternalNotice.) */

 * (On failure, we report the specific problem via pqInternalNotice.)
 */
int
PQsetvalue(PGresult *res, int tup_num, int field_num, char *value, int len)
{
	PGresAttValue *attval;
	const char *errmsg = NULL;

	/* Note that this check also protects us against null "res" */
	if (!check_field_number(res, field_num))
		return false;

	/* Invalid tup_num, must be <= ntups */
	if (tup_num < 0 || tup_num > res->ntups)
	{
		pqInternalNotice(&res->noticeHooks,
						 "row number %d is out of range 0..%d",
						 tup_num, res->ntups);
		return false;
	}

	/* need to allocate a new tuple? */
	if (tup_num == res->ntups)
	{
		PGresAttValue *tup;
		int			i;

		tup = (PGresAttValue *)
			pqResultAlloc(res, res->numAttributes * sizeof(PGresAttValue),
						  true);

		if (!tup)
			goto fail;

		/* initialize each column to NULL */
		for (i = 0; i < res->numAttributes; i++)
		{
			tup[i].len = NULL_LEN;
			tup[i].value = res->null_field;
		}

		/* add it to the array */
		if (!pqAddTuple(res, tup, &errmsg))
			goto fail;
	}

	attval = &res->tuples[tup_num][field_num];

	/* treat either NULL_LEN or NULL value pointer as a NULL field */
	if (len == NULL_LEN || value == NULL)
	{
		attval->len = NULL_LEN;
		attval->value = res->null_field;
	}
	else if (len <= 0)
	{
		attval->len = 0;
		attval->value = res->null_field;
	}
	else