file of record with dynamic array

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3 total messages Started by Shay Mon, 23 Jul 2001 15:43

#310

Author: Shay
Date: Mon, 23 Jul 2001 15:43

55 lines
2675 bytes

hi,
i'm trying to save data (long string with unknown size) to a file.
i need help - i tried to read the posts here about the subject, but i
still don't know what to do.

what i want to do - 
save a record to a file , the record has strings (with known size) &
strings (with UNKNOWN size) & integers.
i tried to declared the unknown sized string as "array of char" or
"string" or "^ ArrayOfCharType", but each time i got in the saved file
a pointer to this vaiable, and i want the data of it.

i had to declared the file variable as "file" and not as "file of
EntryType" due to the problem of finalization.

here is an example : 

type
     EntryType = record
       str1 : string[255];
       str2 : string[255];
       Num1 : integer;
       largeStr : array of char;
    end;  

procedure ...
var
   MyFile : file;
   MyRec : EntryType ;
   sourceStr : string; // a large string that i have from some other
place with unknown size (until i get it)
begin
        sourceStr := getSourceString();
        SetLength(MyRec.largeStr, length(sourceStr));

        // the next line also give me an error, thats why i did a loop
        // MyRec.largeStr := sourceStr;

        for i := 1 to length(sourceStr) do
            begin
                    MyRec.largeStr[i-1] := Char(sourceStr[i]);
            end;

        MyRec.str1 := 'line1';
        MyRec.str2 := 'line2';     
        MyRec.num1 := 123record;
        
        AssignFile(MyFile,'data1.dat');
        rewrite(MyFile,1);
        BlockWrite(MyFile, MyRec, sizeof(MyRec));
        closeFile(MyFile);
end;

thanks,
Shay

Re: file of record with dynamic array

#309

Author: Andy
Date: Tue, 24 Jul 2001 01:01

67 lines
3485 bytes

the problem is that the array is not array but a pointer to the array. So
for example you can use

// write first fields
BlockWrite(file,record,integer(@rec.largeStr)-integer(@rec));
// write your string
leng := high(rec.largeStr)-low(rec.largeStr)+1  // array size;
BlockWrite(file,leng,sizeof(leng)); // you will need it to read
BlockWrite(file, largeStr[low(largestr)],leng); // array itself

"Shay" <shayt@inter.net.il> wrote in message
news:d44d2b3f.0107230743.1051539d@posting.google.com...
> hi,
> i'm trying to save data (long string with unknown size) to a file.
> i need help - i tried to read the posts here about the subject, but i
> still don't know what to do.
>
> what i want to do -
> save a record to a file , the record has strings (with known size) &
> strings (with UNKNOWN size) & integers.
> i tried to declared the unknown sized string as "array of char" or
> "string" or "^ ArrayOfCharType", but each time i got in the saved file
> a pointer to this vaiable, and i want the data of it.
>
> i had to declared the file variable as "file" and not as "file of
> EntryType" due to the problem of finalization.
>
> here is an example :
>
> type
>      EntryType = record
>        str1 : string[255];
>        str2 : string[255];
>        Num1 : integer;
>        largeStr : array of char;
>     end;
>
> procedure ...
> var
>    MyFile : file;
>    MyRec : EntryType ;
>    sourceStr : string; // a large string that i have from some other
> place with unknown size (until i get it)
> begin
>         sourceStr := getSourceString();
>         SetLength(MyRec.largeStr, length(sourceStr));
>
>         // the next line also give me an error, thats why i did a loop
>         // MyRec.largeStr := sourceStr;
>
>         for i := 1 to length(sourceStr) do
>             begin
>                     MyRec.largeStr[i-1] := Char(sourceStr[i]);
>             end;
>
>         MyRec.str1 := 'line1';
>         MyRec.str2 := 'line2';
>         MyRec.num1 := 123record;
>
>         AssignFile(MyFile,'data1.dat');
>         rewrite(MyFile,1);
>         BlockWrite(MyFile, MyRec, sizeof(MyRec));
>         closeFile(MyFile);
> end;
>
> thanks,
> Shay

Re: file of record with dynamic array

#308

Author: Shay
Date: Wed, 25 Jul 2001 13:55

71 lines
3620 bytes

Thank you very much.
shay.

"Andy" <agribanov@paradise.net.nz> wrote in message news:<vI377.211$ww1.12339@news02.tsnz.net>...
> the problem is that the array is not array but a pointer to the array. So
> for example you can use
> 
> // write first fields
> BlockWrite(file,record,integer(@rec.largeStr)-integer(@rec));
> // write your string
> leng := high(rec.largeStr)-low(rec.largeStr)+1  // array size;
> BlockWrite(file,leng,sizeof(leng)); // you will need it to read
> BlockWrite(file, largeStr[low(largestr)],leng); // array itself
> 
> "Shay" <shayt@inter.net.il> wrote in message
> news:d44d2b3f.0107230743.1051539d@posting.google.com...
> > hi,
> > i'm trying to save data (long string with unknown size) to a file.
> > i need help - i tried to read the posts here about the subject, but i
> > still don't know what to do.
> >
> > what i want to do -
> > save a record to a file , the record has strings (with known size) &
> > strings (with UNKNOWN size) & integers.
> > i tried to declared the unknown sized string as "array of char" or
> > "string" or "^ ArrayOfCharType", but each time i got in the saved file
> > a pointer to this vaiable, and i want the data of it.
> >
> > i had to declared the file variable as "file" and not as "file of
> > EntryType" due to the problem of finalization.
> >
> > here is an example :
> >
> > type
> >      EntryType = record
> >        str1 : string[255];
> >        str2 : string[255];
> >        Num1 : integer;
> >        largeStr : array of char;
> >     end;
> >
> > procedure ...
> > var
> >    MyFile : file;
> >    MyRec : EntryType ;
> >    sourceStr : string; // a large string that i have from some other
> > place with unknown size (until i get it)
> > begin
> >         sourceStr := getSourceString();
> >         SetLength(MyRec.largeStr, length(sourceStr));
> >
> >         // the next line also give me an error, thats why i did a loop
> >         // MyRec.largeStr := sourceStr;
> >
> >         for i := 1 to length(sourceStr) do
> >             begin
> >                     MyRec.largeStr[i-1] := Char(sourceStr[i]);
> >             end;
> >
> >         MyRec.str1 := 'line1';
> >         MyRec.str2 := 'line2';
> >         MyRec.num1 := 123record;
> >
> >         AssignFile(MyFile,'data1.dat');
> >         rewrite(MyFile,1);
> >         BlockWrite(MyFile, MyRec, sizeof(MyRec));
> >         closeFile(MyFile);
> > end;
> >
> > thanks,
> > Shay

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