source: trunk/third/nmh/sbr/cpydgst.c @ 12455

/*
 * cpydgst.c -- copy from one fd to another in encapsulating mode
 *           -- (do dashstuffing of input data).
 *
 * $Id: cpydgst.c,v 1.1.1.1 1999-02-07 18:14:08 danw Exp $
 */

#include <h/mh.h>

/*
 * We want to perform the substitution
 *
 *     \n(-.*)\n      -->       \n- \1\n
 *
 * This is equivalent to the sed substitution
 *
 *     sed -e 's%^-%- -%' < ifile > ofile
 *
 *  but the routine below is faster than the pipe, fork, and exec.
 */

#define S1 0
#define S2 1

#define output(c)   if (bp >= dp) {flush(); *bp++ = c;} else *bp++ = c
#define flush()     if ((j = bp - outbuf) && write (out, outbuf, j) != j) \
                        adios (ofile, "error writing"); \
                    else \
                        bp = outbuf


void
cpydgst (int in, int out, char *ifile, char *ofile)
{
    register int i, j, state;
    register char *cp, *ep;
    register char *bp, *dp;
    char buffer[BUFSIZ], outbuf[BUFSIZ];

    dp = (bp = outbuf) + sizeof outbuf;
    for (state = S1; (i = read (in, buffer, sizeof buffer)) > 0;)
        for (ep = (cp = buffer) + i; cp < ep; cp++) {
            if (*cp == '\0')
                continue;
            switch (state) {
                case S1: 
                    if (*cp == '-') {
                        output ('-');
                        output (' ');
                    }
                    state = S2; /* fall */

                case S2: 
                    output (*cp);
                    if (*cp == '\n')
                        state = S1;
                    break;
            }
        }

    if (i == -1)
        adios (ifile, "error reading");
    flush();
}