How Can I Save a Dynamic Array to a FileStream in Delphi? - delphi

Question

I have the following structures in Delphi 2009:
type
IndiReportIndi = record
IndiName: string;
NameNum: integer;
ReportIndiName: string;
end;
var
XRefList: array of IndiReportIndi;
where XRefList is a dynamic array.
I want to save XRefList to a FileStream. How do I do that AND include all the IndiName and ReportIndiName strings so that they will all be retrievable again when I later load from that FileStream?

Answer 1

type
IndiReportIndi = record
IndiName: string;
NameNum: integer;
ReportIndiName: string;
procedure SaveToStream(Stream: TStream);
procedure LoadFromStream(Stream: TStream);
end;
type
TXRefList = array of IndiReportIndi;
function LoadString(Stream: TStream): string;
var
N: Integer;
begin
Result:= '';
Stream.ReadBuffer(N, SizeOf(Integer));
if N > 0 then begin
SetLength(Result, N);
// Stream.ReadBuffer(Result[1], N * SizeOf(Char));
// fast version - see comment by A.Bouchez
Stream.ReadBuffer(Pointer(Result)^, N * SizeOf(Char));
end;
end;
procedure SaveString(Stream: TStream; const S: string);
var
N: Integer;
begin
N:= Length(S);
Stream.WriteBuffer(N, SizeOf(Integer));
if N > 0 then
// Stream.WriteBuffer(S[1], N * SizeOf(Char));
// fast version - see comment by A.Bouchez
Stream.WriteBuffer(Pointer(S)^, N * SizeOf(Char));
end;
procedure IndiReportIndi.LoadFromStream(Stream: TStream);
var
S: string;
begin
IndiName:= LoadString(Stream);
Stream.ReadBuffer(NameNum, SizeOf(Integer));
ReportIndiName:= LoadString(Stream);
end;
procedure IndiReportIndi.SaveToStream(Stream: TStream);
begin
SaveString(Stream, IndiName);
Stream.WriteBuffer(NameNum, SizeOf(Integer));
SaveString(Stream, ReportIndiName);
end;
function LoadXRefList(Stream: TStream): TXRefList;
var
N: Integer;
I: Integer;
begin
Stream.ReadBuffer(N, SizeOf(Integer));
if N <= 0 then Result:= nil
else begin
SetLength(Result, N);
for I:= 0 to N - 1 do
Result[I].LoadFromStream(Stream);
end;
end;
procedure SaveXRefList(Stream: TStream; const List: TXRefList);
var
N: Integer;
I: Integer;
begin
N:= Length(List);
Stream.WriteBuffer(N, SizeOf(Integer));
for I:= 0 to N - 1 do
List[I].SaveToStream(Stream);
end;

Answer 2

Use: http://code.google.com/p/kblib/
type
IndiReportIndi = record
IndiName: string;
NameNum: integer;
ReportIndiName: string;
end;
TXRefList = array of IndiReportIndi;
var
XRefList: TXRefList;
To save whole XRefList to stream use:
TKBDynamic.WriteTo(lStream, XRefList, TypeInfo(TXRefList));
To load it back:
TKBDynamic.ReadFrom(lStream, XRefList, TypeInfo(TXRefList));

Answer 3

var
S: TStream;
W: TWriter;
A: array of IndiReportIndi;
E: IndiReportIndi;
...
begin
S := nil;
W := nil;
try
S := TFileStream.Create(...);
W := TWriter.Create(S);
W.WriteInteger(Length(A));
for E in A do
begin
W.WriteString(E.IndiName);
W.WriteInteger(E.NameNum);
W.WriteString(E.ReportIndiName);
end;
finally
W.Free;
S.Free
end;
end;
To read those data you use a TReader and ReadInteger/ReadString.

Answer 4

Simple TFileStreamEx to save variables
http://forum.chertenok.ru/viewtopic.php?t=4642
Work with them from 2005th year, without any problems...

Answer 5

Just for the answer to be accurate:
Consider taking a look at the TDynArray wrapper, which is able to serialize any record into binary, and also to/from dynamic arrays.
There are a lot of TList-like methods, including new methods (like hashing or binary search).
Very optimized for speed and disk use, works for Delphi 5 up to XE2 - and Open Source.
See also How to store dynamic arrays in a TList?