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