diplodocus.org Git - nmh/blob - sbr/cpydgst.c

   1
   2 /*
   3  * cpydgst.c -- copy from one fd to another in encapsulating mode
   4  *           -- (do dashstuffing of input data).
   5  *
   6  * $Id$
   7  *
   8  * This code is Copyright (c) 2002, by the authors of nmh.  See the
   9  * COPYRIGHT file in the root directory of the nmh distribution for
  10  * complete copyright information.
  11  */
  12
  13 #include <h/mh.h>
  14
  15 /*
  16  * We want to perform the substitution
  17  *
  18  *     \n(-.*)\n      -->       \n- \1\n
  19  *
  20  * This is equivalent to the sed substitution
  21  *
  22  *     sed -e 's%^-%- -%' < ifile > ofile
  23  *
  24  *  but the routine below is faster than the pipe, fork, and exec.
  25  */
  26
  27 #define S1 0
  28 #define S2 1
  29
  30 #define output(c)   if (bp >= dp) {flush(); *bp++ = c;} else *bp++ = c
  31 #define flush()     if ((j = bp - outbuf) && write (out, outbuf, j) != j) \
  32                         adios (ofile, "error writing"); \
  33                     else \
  34                         bp = outbuf
  35
  36
  37 void
  38 cpydgst (int in, int out, char *ifile, char *ofile)
  39 {
  40     register int i, j, state;
  41     register char *cp, *ep;
  42     register char *bp, *dp;
  43     char buffer[BUFSIZ], outbuf[BUFSIZ];
  44
  45     dp = (bp = outbuf) + sizeof outbuf;
  46     for (state = S1; (i = read (in, buffer, sizeof buffer)) > 0;)
  47         for (ep = (cp = buffer) + i; cp < ep; cp++) {
  48             if (*cp == '\0')
  49                 continue;
  50             switch (state) {
  51                 case S1:
  52                     if (*cp == '-') {
  53                         output ('-');
  54                         output (' ');
  55                     }
  56                     state = S2; /* fall */
  57
  58                 case S2:
  59                     output (*cp);
  60                     if (*cp == '\n')
  61                         state = S1;
  62                     break;
  63             }
  64         }
  65
  66     if (i == -1)
  67         adios (ifile, "error reading");
  68     flush();
  69 }