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来源:远方网络 | 2005-12-31 9:46:05 | (有1748人读过)
/-------保存数据部分
procedure TIbStorage.SaveToFile(ADataSet: TDataSet; AFileName: string);
var
Fp: TFileStream;
I : Integer;
Ch: Char;
T1, T2: TDateTime;
Str: string;
begin
if Not FOpenFlag then
begin
showmessage(' 对象没有打开');
Exit;
end;
try
if FileExists(AFileName) then DeleteFile(AFileName);
Fp := TFileStream.Create(AFileName, fmCreate);
Reset;
SaveHead(ADataSet, Fp); //保存头部信息---附加说明
IndexFields(ADataSet); //将数据集的字段信息保存到FFieldName
LoadTableToStream(ADataSet); //保存数据集的数据信息
WriteAStr(Fp, FFieldNames.Text); //存储字段名信息
Ch := '@';
Fp.Write(Ch, 1);
WriteAStr(Fp, FStreamIndex.Text); //存储字段索引列表
Ch := '@';
Fp.Write(Ch, 1);
Fp.CopyFrom(FStream, 0);
finally
Fp.Free;
end;
end;
procedure TIbStorage.SaveHead(ADataSet: TDataSet; Fp: TStream);
Var
I : Integer;
Ch: Char;
begin
if Not ADataSet.Active then ADataSet.Active := True;
WriteAStr(Fp, Flag);
WriteAStr(Fp, FRptTitle);
WriteAStr(Fp, FPageHead);
WriteAStr(Fp, FPageFoot);
FFieldCount := ADataSet.Fields.Count;
FRecordCount := ADataSet.RecordCount;
WriteAStr(Fp, IntToStr(ADataSet.Fields.Count));
WriteAStr(Fp, IntToStr(ADataSet.RecordCount));
Ch := '@';
Fp.Write(Ch, 1);
end;
procedure TIbStorage.IndexFields(ADataSet: TDataSet);
var
I : Integer;
AField: TField;
begin
For I := 0 to ADataSet.Fields.Count - 1 do
begin
AField := ADataSet.Fields[I];
//不用FFieldNames.Values[AField.FieldName] := AField.DisplayLabel;是考虑效率
FFieldNames.Add(AField.FieldName + '=' + AField.DisplayLabel);
FFieldNames.Add(AField.FieldName + 'DataType=' + IntToStr(Ord(AField.DataType)));
end;
end;
procedure TIbStorage.LoadTableToStream(ADataSet: TDataSet);
var
No: Integer;
I, J, Size: Integer;
Tmp, Id, Str : string; //id=string(RecNO) + string(FieldNo)
Len: Integer;
Ch : Char;
BlobStream: TBlobStream;
begin
if Not FOpenFlag then
begin
showmessage(' 对象没有打开');
Exit;
end;
try
ADataSet.DisableControls;
ADataSet.First;
No := 0;
FStreamIndex.Clear;
FStream.Size := 0;
While Not ADataSet.Eof do
begin
No := No + 1;
For J := 0 to ADataSet.Fields.Count - 1 do
begin
Id := Inttostr(NO) + '_' + IntToStr(J);
//建立流的位置的索引, 索引指向: Size#0Content
FStreamIndex.Add(Id + '=' + IntToStr(FStream.Position));
//存储字段信息到流中
SaveFieldToStream(FStream, ADataSet.Fields[J]);
end;
ADataSet.Next;
end;
finally
ADataSet.EnableControls;
end;
end;
//如果一个字段的当前内容为空或者BlobSize<=0,则只写入字段大小为0, 不写入内容
procedure TIbStorage.SaveFieldToStream(AStream: TStream; AField: TField);
var
Size: Integer;
Ch: Char;
XF: TStream;
Str: string;
begin
if AField.IsBlob then
begin
//如何把一个TBlobField字段的内容存储为流
Xf := TBlobStream.Create(TBlobField(AField), bmread);
try
if Xf.Size > 0 then
begin
Size := Xf.Size;
WriteAInteger(AStream, Size);
AStream.CopyFrom(Xf, Xf.Size);
end
else
WriteAInteger(AStream, 0);
finally
XF.Free;
end;
end
else
begin
Str := AField.AsString;
Size := Length(Str);
WriteAInteger(AStream, Size);
if Size <> 0 then
AStream.Write(Pointer(Str)^, Size);
//WriteAstr(AStream, Str);
end;
Ch := '@';
AStream.Write(Ch, 1);
end;
//------------Load Data
procedure TIbStorage.LoadFromFile(AFileName: string);
var
Fp: TFileStream;
Check: string;
begin
Reset;
try
if Not FileExists(AFileName) then
begin
showmessage(' 文件不存在:' + AFileName);
Exit;
end;
Fp := TFileStream.Create(AFileName, fmOpenRead);
Check := ReadAStr(Fp);
if Check <> Flag then
begin
Application.MessageBox(' 非法文件格式', '错误', Mb_Ok + Mb_IconError);
Exit;
end;
GetHead(Fp);
GetFieldNames(Fp);
GetIndex(Fp);
FStream.CopyFrom(Fp, Fp.Size-Fp.Position);
finally
Fp.Free;
end;
end;
procedure TIbStorage.GetHead(Fp: TFileStream);
begin
FRptTitle := ReadAStr(Fp);
FPageHead := ReadAstr(Fp);
FPageFoot := ReadAstr(Fp);
FFieldCount := ReadAInteger(Fp);
FRecordCount := ReadAInteger(Fp);
if ReadAChar(Fp) <> '@' then showmessage('GetHead File Error');
end;
procedure TIbStorage.GetFieldNames(Fp: TFileStream);
var
Ch: Char;
Str: string;
begin
Str := '';
Str := ReadAStr(Fp);
FFieldNames.CommaText := Str;
Ch := ReadAChar(Fp);
if Ch <> '@' then Showmessage('When get fieldnames Error');
end;
procedure TIbStorage.GetIndex(Fp: TFileStream);
var
Ch: Char;
Str: string;
begin
Str := '';
Str := ReadAStr(Fp);
FStreamIndex.CommaText := Str;
Ch := ReadAChar(Fp);
if Ch <> '@' then Showmessage('When Get Field Position Index Error');
end;
//---------Read Field's Value Part
function TIbStorage.GetFieldValue(ARecordNo, FieldNo: Integer): string;
var
Id, T : string;
Pos: Integer;
Len, I : Integer;
Er: Boolean;
begin
Result := '';
Er := False;
if ARecordNo > FRecordCount then
Er := true; //ARecordNo := FRecordCount;
if ARecordNo < 1 then
Er := True; // ARecordNo := 1;
if FieldNo >= FFieldCount then
Er := True; // FieldNo := FFieldCount - 1;
if FieldNo < 0 then
Er := True; //FieldNo := 0;
if Er then
begin
Showmessage('记录号或者字段标号越界');
Exit;
end;
if FFieldCount = 0 then Exit;
Id := Inttostr(ARecordNO) + '_' + IntToStr(FieldNo);
Pos := StrToInt(FStreamIndex.Values[Id]);
FStream.Position := Pos;
//取得字段内容的长度
Len := ReadAInteger(FStream);
if Len > 0 then
Result := ReadBStr(FStream, Len);
if ReadAChar(FStream) <> '@' then
Showmessage('When Read Field, Find Save Format Error');
end;
procedure TIbStorage.FieldStream(ARecordNo, FieldNo: Integer; var AStream: TStream);
var
Id, T : string;
Pos: Integer;
Len, I : Integer;
Er: Boolean;
begin
Er := False;
if ARecordNo > FRecordCount then
Er := true; //ARecordNo := FRecordCount;
if ARecordNo < 1 then
Er := True; // ARecordNo := 1;
if FieldNo >= FFieldCount then
Er := True; // FieldNo := FFieldCount - 1;
if FieldNo < 0 then
Er := True; //FieldNo := 0;
if Er then
begin
TDsException.Create('GetFieldValue函数索引下标越界');
Exit;
end;
if FFieldCount = 0 then Exit;
Id := Inttostr(ARecordNO) + IntToStr(FieldNo);
Pos := StrToInt(FStreamIndex.Values[Id]);
FStream.Position := Pos;
Len := ReadAInteger(FStream);
AStream.CopyFrom(FStream, Len);
end;
function TIbStorage.GetFieldName(AIndex: Integer): string; //取得字段名称
begin
//存储的字段和数据类型各占一半
if ((AIndex < 0) or (AIndex >= FFieldNames.Count div 2)) then
Application.MessageBox(' 取字段名索引越界', '程序 错误',
Mb_Ok + Mb_IconError)
else
Result := FFieldNames.Names[AIndex*2];
end;
function TIbStorage.GetFieldDataType(AIndex: Integer): TFieldType; //取得字段名称
begin
//存储的字段和数据类型各占一半
if ((AIndex < 0) or (AIndex >= FFieldNames.Count div 2)) then
Application.MessageBox(' 取字段数据类型索引越界', '程序 错误',
Mb_Ok + Mb_IconError)
else
Result := TFieldType(StrToInt(FFieldNames.Values[FFieldNames.Names[AIndex*2+1]]));
end;
function TIbStorage.GetDisplayLabel(AIndex: Integer): string; //取得字段显示名称
begin
if ((AIndex < 0) or (AIndex >= FFieldNames.Count)) then
Application.MessageBox(' 取字段名索引越界', '程序 错误',
Mb_Ok + Mb_IconError)
else
Result := FFieldNames.Values[GetFieldName(AIndex)];
end; end.
通过测试，该控件对Ttable,Tquery, TaodTable, TadoQuery, TibTable, TibQuery等常用的数据集控件等都能较好的支持，并且具有较好的效率（测试：1100条人事记录，23个字段存储为文件约用时2秒钟）。
四、控件的基本使用方法
1．存储数据集中的数据到文件
IbStorage1.Open; //创建存储流
IbStorage1.SaveToFile(AdataSet, Afilename);
2．从文件中读出数据信息
IbStorage1.Open;
IbStorage1.LoadFromFile(AfileName);
3．对数据报存储控件中数据的访问
Value := IbStorage1.Fields[ArecNo, AfieldNo]; //字符串类型
其它略。
五、结束语
通过编写此数据报存储控件，较好地解决了数据库程序中数据的存储和交换问题，为数据库程序的开发提供了一种实用的控件。
该控件在Windows98，Delphi5开发环境下调试通过。
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