Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.postscript > #1874

Re: Regexp expression that selects PostScript strings

Show all headers | View raw

On Saturday, May 3, 2014 11:42:33 PM UTC-5, luser- -droog wrote:
> On Saturday, May 3, 2014 7:52:38 PM UTC-5, tlvp wrote:
> 
> > On Sat, 3 May 2014 13:50:42 -0700 (PDT), jdaw1 wrote:
> 
> > 
> > > Does anybody have to hand a regexp expression that selects PostScript strings?
> > > 
> > > As a simple non-example, \([^\)]*\) fails to cope with the likes of 
> > > 
> > >     (and (as an aside) this should be mentioned)
> > > 
> > > and also with strings containing \( or \).
> > 
> > Why would you have expected it to cope with the likes of that?
> > What it seems designed to  cope with is the likes of this:
> > 
> > :  (and )as an aside) this should be mentioned)
> > 
> 
> Not sure about the example, but I think in general
> regular expressions cannot handle postscript strings
> because of the possibility of nested un-escaped parens.

My own code for validating a postscript "statement" 
containing complete but arbitrarily nested parens,
braces, and angle-brackets, is a push-down automaton,
the next class up from the finite-automata that can
process regular expressions.

http://code.google.com/p/xpost/source/browse/src/lib/xpost_file.c#198
/* pinch-off a tmpfile containing one "statement" from file. */
 
/*@null@*/
 
static
 
int statementedit(FILE *in, FILE **out)
 
{
 
    FILE *fp;
 
    int c;
 
    char nest[MAXNEST] = {0}; /* any of {(< waiting for matching >)} */
 
    int defer = -1; /* defer is a flag (-1 == false)
 
                       and an index into nest[] */
 

 
    c = fgetc(in);
 
    if (c == EOF)
 
    {
 
        return undefinedfilename;
 
    }
 
#ifdef DEBUG_FILE
 
        printf("tmpfile (fdopen)\n");
 
#endif
 
    fp = f_tmpfile();
 
    if (fp == NULL) {
 
        XPOST_LOG_ERR("tmpfile() returned NULL");
 
        return ioerror;
 
    }
 
    do {
 
        if (defer > -1) {
 
            if (defer > MAXNEST)
 
            {
 
                return syntaxerror;
 
            }
 
            switch(nest[defer]) { /* what's the innermost nest? */
 
            case '{': /* within a proc, can end proc or begin proc, string, hex */
 
                switch (c) {
 
                case '}': --defer; break;
 
                case '{':
 
                case '(':
 
                case '<': nest[++defer] = c; break;
 
                } break;
 
            case '(': /* within a string, can begin or end nested paren */
 
                switch (c) {
 
                case ')': --defer; break;
 
                case '(': nest[++defer] = c; break;
 
                case '\\': fputc(c, fp);
 
                           c = fgetc(in);
 
                           if (c == EOF) goto done;
 
                           goto next;
 
                } break;
 
            case '<': /* hexstrings don't nest, can only end it */
 
                if (c == '>') --defer; break;
 
            }
 
        } else switch (c) { /* undefined, can begin any structure */
 
        case '{':
 
        case '(':
 
        case '<': nest[++defer] = c; break;
 
        case '\\': fputc(c, fp);
 
                   c = fgetc(in); break;
 
        }
 
        if (c == '\n') {
 
            if (defer == -1) goto done;
 
            { /* sub-prompt */
 
                int i;
 
                for (i=0; i <= defer; i++)
 
                    putchar(nest[i]);
 
                fputs(".:", stdout);
 
                fflush(NULL);
 
            }
 
        }
 
next:
 
        fputc(c, fp);
 
        c = fgetc(in);
 
    } while(c != EOF);
 
done:
 
    fseek(fp, 0, SEEK_SET);
 
    //return fp;
 
    *out = fp;
 
    return 0;
 
}
 

Back to comp.lang.postscript | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Regexp expression that selects PostScript strings jdaw1 <jdawiseman@gmail.com> - 2014-05-03 13:50 -0700
  Re: Regexp expression that selects PostScript strings tlvp <mPiOsUcB.EtLlLvEp@att.net> - 2014-05-03 20:52 -0400
    Re: Regexp expression that selects PostScript strings luser- -droog <mijoryx@yahoo.com> - 2014-05-03 21:42 -0700
      Re: Regexp expression that selects PostScript strings luser- -droog <mijoryx@yahoo.com> - 2014-05-04 00:07 -0700
      Re: Regexp expression that selects PostScript strings jdaw1 <jdawiseman@gmail.com> - 2014-05-04 07:48 -0700
  Re: Regexp expression that selects PostScript strings jdaw1 <jdawiseman@gmail.com> - 2014-05-05 08:48 -0700
    Re: Regexp expression that selects PostScript strings jdaw1 <jdawiseman@gmail.com> - 2014-05-05 08:58 -0700
      Re: Regexp expression that selects PostScript strings luser- -droog <mijoryx@yahoo.com> - 2014-05-06 09:58 -0700

csiph-web