write data into binary file

[opera]

if I want to write integer 100 and double 123.456 into a binary file.do I need to first assign-rewrite-blockwrite-close to write 100 and then again assign-rewrite-blockwrite-close to write 123.456? is there concise method? thank you.

[taazz]

pseudo code
assignfile();
rewrite(file);
blockwrite(myinteger,sizeof(myinteger));
blockwrite(myDouble,sizeof(myDouble));
blockwrite(length(myString), sizeof(integer));
blockwrite(myString[1],length(myString));

Keep on using blockwrite as needed then close the file.

[exdatis]

Thanks, taazz!

[opera]

pseudo code
assignfile();
rewrite(file);
blockwrite(myinteger,sizeof(myinteger));
blockwrite(myDouble,sizeof(myDouble));
blockwrite(length(myString), sizeof(integer));
blockwrite(myString[1],length(myString));

Keep on using blockwrite as needed then close the file.

I write the following code:

program test;
var
f:file;
a:integer;
b:double;
begin
a:=100;
b:=123.456;
assign(f,'testfile') ;
rewrite(f);
blockwrite(f,a,sizeof(a));
blockwrite(f,b,sizeof(b));
close(f);
end.

after run, the testfile is 1280 bytes,what is wrong with it?

[taazz]

Source :
http://www.freepascal.org/docs-html/rtl/system/rewrite.html

From the description you need to do something like.

Code: [Select]

program test;
var
  f:file;
  a:integer;
  b:double;
begin
  a:=100;
  b:=123.456;
  assign(f,'testfile') ;
  rewrite(f,1);//<------ changed to 1 byte block instead of 128 bytes that is the default.
  blockwrite(f,a,sizeof(a));
  blockwrite(f,b,sizeof(b));
  close(f);
end.


[opera]

thank you, taazz

[WickedDum]

Should you use a Try-Finally around the whole Assign-to-Close block or per line so you know what failed?