String parsing in stap script

String parsing in stap script

[Mike Mason]

I'm trying to figure out how to parse a string in a stap script.  Ideally, I'd like a function like strsep() where I pass in a string and delimiter and get back a token and a pointer to the string past the token. Given that a stap function can only pass back one value, I don't see how to accomplish this.  Any suggestions or is this just not possible?

BTW, my initial reason for wanting this is to pass an array from a shell script to a stap script.  I figure I can just pass it as one long delimited string, then parse it on the stap side to get it back in array form.

- Mike

Re: String parsing in stap script

[Jim Keniston]

On Thu, 2006-11-09 at 11:25, Mike Mason wrote:
> I'm trying to figure out how to parse a string in a stap script.  Ideally,
> I'd like a function like strsep() where I pass in a string and delimiter
> and get back a token and a pointer to the string past the token. Given
> that a stap function can only pass back one value, I don't see how to
> accomplish this.  Any suggestions or is this just not possible?

Have you considered storing the parsing context in a struct (created via
embedded C) and passing around a pointer to that?

Jim

> 
> BTW, my initial reason for wanting this is to pass an array from a shell
> script to a stap script.  I figure I can just pass it as one long
> delimited string, then parse it on the stap side to get it back in array
> form.
> 
> - Mike
> 

Re: String parsing in stap script

[Frank Ch. Eigler]

Mike Mason <mmlnx@us.ibm.com> writes:

> I'm trying to figure out how to parse a string in a stap script.
> Ideally, I'd like a function like strsep() where I pass in a string
> and delimiter and get back a token and a pointer to the string past
> the token. [...]

If you're willing to sacrifice concurrent use of the same tokenizing
process, you could write a single function, something like:

function tokenize:string (input:string, separator:string) %{
   static char tokenstr[MAXSTRINGLEN];
   static char* tokenptr = & tokenstr[0];
   char *tokenptr_start = tokenptr;
   if (THIS->input[0]) {
     strncpy (tokenstr, THIS->input, MAXSTRINGLEN);
     tokenptr = & tokenstr[0];
   }
   /* ... now call strsep or whatever on tokenstr/tokenptr  ... */
   if (/* token found */)
     strncpy (THIS->__retvalue, tokenptr_start, (tokenptr - tokenptr_start));
   /* else THIS->__retvalue is already empty */
%}


- FChE