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To:	culliton@srg.srg.af.mil (Tom Culliton x2278)
Subject: Re: wishlist 
Cc:	rc@hawkwind.utcs.toronto.edu
Date:	Wed, 26 May 1993 13:26:56 -0400
From:	Alan Watson <alan@oldp.astro.wisc.edu>
X-Mts: smtp

You can't use sed, as you don't know how much it buffers stuff up internally.
Same with awk.

You cannot use ifs = $nl { foo = `{ cat } }, as you lose blank lines
and cannot tell if the final line ends in a $nl or not.  I had enough
of that kind of stuff 

I coded this up in about 10 minutes last night -- it works as a
technology demonstrator, but (a) the C code needs re-writing to read N
chars first and then one char at a time until the end of the line, and
(b) it all needs some better error checking.

bufread reads a line at a time into the variable, including any
trailing newline, and sets the variable to () at EOF.

Hope this helps you get a start,

Alan.

fn copy {
   @ {
      exec <$1 >$2
      while ( bufread line ibuf && ! ~ $#line 0 ) 
	 bufwrite line obuf
      bufflush obuf
   }
}

fn bufread {
   _var = $1 _buf = $2 {
      if ( ~ $#$_buf 0 ) {
	 ifs = () { eval '*' '=' `{ ./buffill } }
      } else {
	 * = $$_buf
      }
      $_var = $1
      if ( ! ~ $#* 0 )
	 shift
      $_buf = $*
   }
}

fn bufwrite {
   _var = $1 _buf = $2 {
      if ( ~ $#$_buf 4 ) {
	 bufflush $_buf
	 $_buf = ()
      }
      $_buf = ( $$_buf $$_var )
   }
}

fn bufflush {
   _buf = $1 _text = () {
      * = $$_buf
      while ( ! ~ $#* 0 ) {
	 _text = $text^$1
	 shift
      }
      echo -n $text
   }
}

buffill.c:


#include <unistd.h>

#define N 256

#define writestr(fd,s) (write ((fd),(s), sizeof (s) - 1))

int main ()
{
   char c;
   char lastc;
   int n;

   writestr (1, "( ");

   n = 0;
   while (n < N || c != '\n') {
      if (read (0, &c, 1) != 1)
	 break;
      if (n == 0 || lastc == '\n')
	 writestr (1, "'");
      if (c == '\'')
	 writestr (1, "''");
      else if (c == '\n')
	 writestr (1, "\n' ");
      else
	 write (1, &c, 1);
      lastc = c;
      n++;
   }

   if (n != 0 && c != '\n')
      writestr (1, "' ");

   writestr (1, ")");

   return 0;
}