Method perform

src/dsql/ExprNodes.cpp:11834–11985

}

dsc* SubstringNode::perform(thread_db* tdbb, impure_value* impure, const dsc* valueDsc,
	const dsc* startDsc, const dsc* lengthDsc)
{
	SINT64 sStart = MOV_get_long(tdbb, startDsc, 0);
	SINT64 sLength = MOV_get_long(tdbb, lengthDsc, 0);

	if (sLength < 0)
		status_exception::raise(Arg::Gds(isc_bad_substring_length) << Arg::Num(sLength));

	if (sStart < 0)
	{
		sLength = MAX(sLength + sStart, 0);
		sStart = 0;
	}

	FB_UINT64 start = FB_UINT64(sStart);
	FB_UINT64 length = FB_UINT64(sLength);

	dsc desc;
	DataTypeUtil(tdbb).makeSubstr(&desc, valueDsc, startDsc, lengthDsc);

	if (desc.isText() && length > MAX_STR_SIZE)
		length = MAX_STR_SIZE;

	ULONG dataLen;

	if (valueDsc->isBlob())
	{
		// Source string is a blob, things get interesting.

		fb_assert(desc.dsc_dtype == dtype_blob);

		desc.dsc_address = (UCHAR*) &impure->vlu_misc.vlu_bid;

		blb* newBlob = blb::create(tdbb, tdbb->getRequest()->req_transaction, &impure->vlu_misc.vlu_bid);

		blb* blob = blb::open(tdbb, tdbb->getRequest()->req_transaction,
			reinterpret_cast<bid*>(valueDsc->dsc_address));

		HalfStaticArray<UCHAR, BUFFER_LARGE> buffer;
		CharSet* charSet = INTL_charset_lookup(tdbb, valueDsc->getCharSet());

		const FB_UINT64 byte_offset = start * charSet->maxBytesPerChar();
		const FB_UINT64 byte_length = length * charSet->maxBytesPerChar();

		if (charSet->isMultiByte())
		{
			buffer.getBuffer(MIN(blob->blb_length, byte_offset + byte_length));
			dataLen = blob->BLB_get_data(tdbb, buffer.begin(), buffer.getCount(), false);

			HalfStaticArray<UCHAR, BUFFER_LARGE> buffer2;
			buffer2.getBuffer(dataLen);

			dataLen = charSet->substring(dataLen, buffer.begin(),
				buffer2.getCapacity(), buffer2.begin(), start, length);
			newBlob->BLB_put_data(tdbb, buffer2.begin(), dataLen);
		}
		else if (byte_offset < blob->blb_length)