My software developed under Delphi 7.0 has been upgraded and developed under Delphi 2010 RAD Studio XE. It also saves or writes user's settings into binary files. The problem I am running into is that my Delphi 2010 application or software is expected to read binary files created by Delphi 7.0 application, but Delphi 2010 application has problem reading the binary file. Both of these software are copy of each other.
I did set the Record Field Alignment option for the project at 1 on Delphi 7.0 and byte on Delphi 2010.
I am always running into exception "read beyond end of line," when the software reads the binary file.
I read and write a binary file by doing the following.
Writing into a binary file:
procedure WriteUnitFile;
var
unitFile: File;
x:integer;
FileHeader:TFileHeader;
begin
if not DemoMode then
begin
FileHeader.id := 'UnitFile';
FileHeader.version := 7;
if fileexists(basedir+unitfilename) then
BackupFile(basedir+unitfilename);
AssignFile(unitFile,baseDir+unitfilename);
if UnitList.Count > 0 then
begin
Rewrite(unitFile,1);
BlockWrite(unitFile, FileHeader, SizeOf(FileHeader));
for x := 0 to UnitList.Count - 1 do
begin
TUnit(UnitList[x]).Write(unitFile);
end;
end
else
DeleteFile(baseDir+unitfilename);
CloseFile(unitFile);
end;
end;
Reading from a binary file:
procedure ReadUnitFile;
var
unitFile:File;
newUnit,simUnit:TUnit;
ut,TypeCard:TUnitType;
New_Ver_File:TFileHeader;
Address:SmallInt;
State:TUnitState;
SubAddress:SmallInt;
MyfDefs:array[1..20] of SmallInt;
fDefs:array[1..16] of SmallInt;
begin
if FileExists(baseDir + unitfilename) then
begin
oneUnit := false;
AssignFile(unitFile,baseDir+unitfilename);
AssignFile(newUnitFile,baseDir+Dummyfilename);
Reset(unitFile,1);
BlockRead(unitFile,New_Ver_File,SizeOf(New_Ver_File));
Reset(UnitFile,1);
BlockRead(UnitFile,New_Ver_File,SizeOf(New_Ver_File));
while not Eof(UnitFile) do
begin
BlockRead(UnitFile,ut,SizeOf(ut));
case ut of
tutSimulator:newUnit := TSimulator.Create;
tutDX2202:newUnit := TDX2202.Create;
tutDX8884CS:newUnit:=TDX8884CS.Create;
tutDX8F44F: newUnit := TDX8F44F.Create;
tutDX0008:newUnit := TDX0008.Create;
tutDX0800:newUnit := TDX0800.Create;
tutDX8000:newUnit := TDX8000.Create;
tutDX1000:newUnit := TDX1000.Create;
tutDX0100:newUnit := TDX0100.Create;
tutDX4404:newUnit := TDX4404.Create;
tutDX0020:newUnit := TDX0020.Create;
tutDX0080:newUnit := TDX0080.Create;
tutDX8814:newUnit := TDX8814.Create;
tutDX8814CS:newUnit := TDX8814CS.Create;
tutDX8884:newUnit := TDX8884.Create;
else
newUnit := TUnit.Create;
end;
newUnit.Read(unitFile);
if DemoMode then
begin
if oneUnit = true then
begin
simUnit := TSimulator.Create;
simUnit.Assign(newUnit);
newUnit.Free;
newUnit := simUnit;
end
else
begin
oneUnit := true;
end;
end;
unitList.Add(newUnit);
end;
CloseFile(unitfile);
UnitsDlg.UnitGrid.RowCount := unitList.Count+1;
if UnitsDlg.UnitGrid.RowCount > 1 then
UnitsDlg.UnitGrid.FixedRows := 1;
UnitsDlg.FillIn;
end
else
begin
UnitsDlg.UnitGrid.RowCount := 1;
end;
end;
UPDATE: Here is the user-defined datatypes:
TFileHeader = record
id:string[32];
version:SmallInt;
end;
TUnitType = (tutUnused,tutSimulator,tutDX2202,tutDX0008,tutDX0800,tutDX8000,
tutDX1000,tutDX4404,tutDX0020,tutDX8814,tutDX8814CS,
tutDX8884,tutDX8884CS,tutDX8f44f,tutDX0080,tutDX0100,tutLast);
TUnitState = (tusDisabled,tusEnabled);
TUnit = class(TObject)
changeLink:TUnit;
Address: SmallInt;
SubAddress:SmallInt;
State:TUnitState;
uType:TUnitType;
RegCnt:integer;
fRegs:array[1..20] of SmallInt;
fDefs:array[1..20] of SmallInt;
MsgCnt:LongWord;
RxCnt:LongWord;
BreakCnt: LongWord;
LineErrCnt: LongWord;
OtherErrCnt:LongWord;
TimeoutCnt: LongWord;
BadMsgErrCnt:LongWord;
XSumErrCnt:LongWord;
OutsFlag:Boolean;
CommBits:LongWord;
OfflineCnt:integer;
Online:Boolean;
CurReg:integer;
selectedonce,usedIP:Boolean;
LastDigitalOut,LastDigitalIn,
CurRegOut,umsglen,urmsglen,
dummycount,Unitlocation,
CommLocation:integer;
private
public
followed by list of procedures and functions...
end;
Is there something I am missing or not understanding very well?
One thing I did forget to mention is that Delphi 2010 application reads and writes into binary files just fine without making any changes to the code, but it has problem only when reading files created by Delphi 7.0. application.Obviously, this question is related to Record Field Alignment. So, what should I set it on my Delphi 2010 (Byte, Word, Double Word, Quad Word), if Delphi 7.0 is set at 1.Thanks in advance.
Answer:The key is in the
TFileHeader declaration (and maybe the
TUnit and
TUnitType declaration). You should add these definitions to your question.
If you define a pure string in either of these records, you need to use
ShortString instead of
String in Delphi 2010 to make it work.
String in Delphi 7 = 1 byte per char.
String in Delphi 2010 = 2 bytes per char.
Update:
Your last update doesn't really reveal any new information, but the
fDefs variable in the
ReadUnitFile procedure is defined as an
array[1..16] of SmallInt;, but in your
TUnit class,
fDefs is an
array[1..20] of SmallInt;?
The
fDefs variable doesn't seem to be used, but this might be the difference that causes the EOL error?
You should define arrays like this as a common
Type, anyway, to ensure that they can be passed around and assigned to each other as compatible types (eg. as parameters in methods).
Yet an update:
The error is not in the strings, but in the Size of
TObject.
In Delphi 2009,
TObject increased the size from 4 bytes to 8 bytes.
The first 4 bytes is a pointer to the objects
VMT (as it has been for a long time), and in the last 4 bytes (IIRC), it is possible to contain a reference to a synchronization monitor.
Have a look at this nice article:
http://blogs.teamb.com/craigstuntz/2009/03/25/38138/