delphi - 读取TMemoryStream时出现访问冲突错误

Question

我在读取 TMemoryStream 时收到“访问冲突”错误。

        with Dataset do
        begin
            Edit;
            FieldByName('FK_ID').AsInteger := aID;
            FieldByName('FINGERNO').AsInteger := aFP.FPIndex;
            FieldByName('FINGERTEMPLATE').AsString := aFP.FPBuffer; {This works fine}
            TBlobField(FieldByName('FINGERTEMPLATE')).LoadFromStream(aFP.FPData); {Access Violation Error}

            ApplyUpdates(0);
        end;

这是获取 TMemoryStream (FPData) 的代码。

type
    TFingerPrint = record
    FPIndex : integer;
    FPData : TMemoryStream;
    FPBuffer : String;
end;

function TMachine.SetFingerPrintStream(
      EmployeeRecord : PEmployeeRecord;  EmployeeFP : PFingerPrint): PEmployeeRecord;
var
    sbuffer: ansistring;
    FPIndex,i : Integer;
    FPList, FPDetailedList, BufferList : TStringList;
    FingerprintStream: TMemoryStream;
    FingerPrint: array of Byte;
    FingerPrintLength: Integer;
    pfilter  : PAnsiChar;
    Adata : String;
    Writer: TBinaryWriter;
begin
    EmployeeRecord.Fingerprints := TList.Create;
    FPList := TStringList.Create;
    FPDetailedList  := TStringList.Create;
    FPDetailedList.StrictDelimiter := True;
    FPDetailedList.Delimiter := ',';

    // BufferList := TStringList.Create;

    pfilter   :=  pAnsiChar(AnsiString('Pin=' + EmployeeRecord.EnrollNumber));
    sbuffer   :=  GetTurnsileDeviceInfo('templatev10','*',pfilter,'');

   // BufferList.Add(sbuffer);
   // BufferList.SaveToFile('C:\BufferText.txt');

    try
        FPList.Text :=  sbuffer;
        for FPIndex := 1 to FPList.Count -1 do
        begin
            FPDetailedList.DelimitedText :=  FPList[FPIndex];

            FingerprintStream := TMemoryStream.Create;
            try
                AData       :=  FPDetailedList[5];

                Assert(AData <> '');
                i := 1;
                while i <= Length(AData) do
                  if AData[i] = #0 then
                    Delete(AData, i, 1)
                  else
                    Inc(i);

                FingerPrintLength := Length(AData);
                SetLength(FingerPrint, FingerPrintLength);
                Writer := TBinaryWriter.Create(FingerprintStream);
                try
                    Writer.Write(TEncoding.Default.GetBytes(AData));
                finally
                    Writer.Free;
                end;

                //FingerprintStream.SaveToFile('C:\StreamTest.txt');

                new(EmployeeFP);
                EmployeeFP.FPIndex := FPIndex -1;
                EmployeeFP.FPData  := FingerprintStream;
                EmployeeFP.FPBuffer := sbuffer;
                EmployeeRecord.Fingerprints.Add(EmployeeFP);
            finally
                FingerprintStream.Free;
            end;
        end;
    finally
        FPList.Free;
        FPDetailedList.Free;
    //    BufferList.Free;
        Result := EmployeeRecord;
    end;
end;

缓冲区/流数据示例(BufferText.txt):

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

我也尝试将 MemoryStream 转换为不同的编码(ASCII、UTF8、ANSI)，但仍然收到错误。

Answer 1

看看这个:

EmployeeFP.FPData  := FingerprintStream;

接下来是:

FingerprintStream.Free;

您已经销毁了流，因此 FPData 引用了一个已被销毁的对象。您的运行时错误就是由此造成的。

您需要确保该流对象的生命周期足以满足您对它的所有使用。

您的代码相当长并且有些复杂。可能还有其他错误，但我没有搜索过。