Method makeSubstr

src/jrd/DataTypeUtil.cpp:287–328

void DataTypeUtilBase::makeSubstr(dsc* result, const dsc* value, const dsc* offset, const dsc* length)
{
	result->clear();

	if (value->isNull())
	{
		result->makeNullString();
		return;
	}

	if (value->isBlob())
	{
		result->dsc_dtype = dtype_blob;
		result->dsc_length = sizeof(ISC_QUAD);
		result->setBlobSubType(value->getBlobSubType());
	}
	else
	{
		// Beware that JRD treats substring() always as returning CHAR
		// instead of VARCHAR for historical reasons.
		result->dsc_dtype = dtype_varying;
	}

	result->setTextType(value->isText() || value->isBlob() ? value->getTextType() : CS_ASCII);
	result->setNullable(value->isNullable() ||
		(offset && offset->isNullable()) ||
		(length && length->isNullable()));

	if (result->isText())
	{
		ULONG len = convertLength(value, result);

		if (length && length->dsc_address)	// constant
		{
			SLONG constant = CVT_get_long(length, 0, JRD_get_thread_data()->getAttachment()->att_dec_status, ERR_post);
			fb_assert(constant >= 0);
			len = MIN(len, MIN(MAX_STR_SIZE, ULONG(constant)) * maxBytesPerChar(result->getCharSet()));
		}

		result->dsc_length = fixLength(result, len) + static_cast<USHORT>(sizeof(USHORT));
	}
}


bool DataTypeUtilBase::makeBlobOrText(dsc* result, const dsc* arg, bool force)