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

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