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