Corrupted strings

[LemonParty]

Hello.

Let's say we have this code:

Code: Pascal  [Select][+][-]

1. var
2.   S: String = '12345';
3. begin
4.   S[3]:= #0;
5. end.
6.  

Is string after this manipulation become corrupted? How should be processed zeroes in the middle of the string?

[marcov]

A Pascal string can contain any character as the length is stored separately, so that would simply be a pascal string with a null character in third position.

However since many GUI and console libraries are C based, they often can't deal with nulls, as they see it as the end of a string.

So in summary, that construct is fine, but displaying it can be troublesome.

[jamie]

Code: Pascal  [Select][+][-]

1. SelLength(S, Pos(#0,S));
2.  

Something like that.

[LemonParty]

Thank you.

[Aruna]

Hello.

Let's say we have this code:

Code: Pascal  [Select][+][-]

1. var
2.   S: String = '12345';
3. begin
4.   S[3]:= #0;
5. end.
6.  

Is string after this manipulation become corrupted? How should be processed zeroes in the middle of the string?

You are replacing '3' (the third character) with #0. So internally, the string bytes become:

S[1] = '1'
S[2] = '2'
S[3] = #0
S[4] = '4'
S[5] = '5'

The length of S is still 5. Nothing is automatically truncated. The string is not corrupted, but you need to be careful when interfacing with routines that expect null-terminated strings. I have attached a zip for you to play around with. Have fun!