Так вот обнаружилось на Ib7.1 sp2 и Ib 7.5, что если второй парметр передается null, то UDF всегда возвращает null. Вне зависимости от того что пишем в udf.DECLARE EXTERNAL FUNCTION BCOMMAUNION
BLOB,
BLOB,
BLOB
RETURNS PARAMETER 3
ENTRY_POINT 'BCommaUnion' MODULE_NAME 'oeudf.dll';
Код: Выделить всё
type
PBlob = ^TBlob;
TBlob = record
GetSegment: function(Handle: pointer; Buffer: PChar; MaxLength: integer; var ReadLength: integer): WordBool; cdecl;
Handle: pointer; // handle
SegCount, // number of segments
MaxSegLength, // max length of segment
TotalLength: integer; // total blob length
PutSegment: procedure(Handle: pointer; Buffer: PChar; Length: integer); cdecl;
end;
const
MaxBlobPutLength = 80;
MaxVarCharLength = 32767;
MaxResultStringLength = 8190;
{ udfs }
function FillBuffer(var Blob: TBlob; Buf: PChar; FreeBufLen: integer; var ReadLen: Integer): boolean;
var
EndOfBlob: boolean;
FreeBufLenX, GotLength: integer;
begin
try
ReadLen := 0;
repeat
GotLength := 0; { !?! }
if FreeBufLen > MaxBlobPutLength
then FreeBufLenX := MaxBlobPutLength
else FreeBufLenX := FreeBufLen;
with Blob do
EndOfBlob := not GetSegment(Handle, Buf+ReadLen, FreeBufLenX, GotLength);
Inc(ReadLen, GotLength);
Dec(FreeBufLen, GotLength);
until EndOfBlob or (FreeBufLen = 0);
except
EndOfBlob := True;
end;
Buf[ReadLen] := #0;
Result := EndOfBlob;
end;
function ReadBlob(var Blob: TBlob): string;
var
ReadLen: Integer;
begin
with Blob do
if Assigned(Handle) and (TotalLength > 0) then
begin
SetLength(Result, TotalLength);
FillBuffer(Blob, PChar(Result), TotalLength, ReadLen);
SetLength(Result, ReadLen);
end else
Result := '';
end;
procedure WriteBlob(var Blob: TBlob; const S: string);
var
SLen, PutLen: integer;
PS: PChar;
begin
SLen := length(S);
PS := PChar(S);
if not Assigned(Blob.Handle) then
Exit;
if SLen = 0 then
begin
PutLen := 0;
with Blob do
PutSegment(Handle, PS, PutLen);
end else
begin
while SLen > 0 do
begin
if SLen > MaxBlobPutLength then
PutLen := MaxBlobPutLength
else
PutLen := SLen;
with Blob do
PutSegment(Handle, PS, PutLen);
dec(SLen, PutLen);
inc(PS, PutLen);
end;
end;
end;
procedure BCommaUnion(Comma1, Comma2, Res: PBlob);
begin
WriteBlob(Res^, ReadBlob(Comma1^) + ReadBlob(Comma2^));
end;
Код: Выделить всё
select BlobToStr(BCOmmaUnion(Props, StrToBlob('800'))) as Props from classes where Props is null