Add col command

col is used to display troff documents in ttys, removing the reverse
line feeds generated by .2C in ms. This implementation keeps the limit
of 256 lines of 800 characteres of the original implementation.

col.c

@@ -0,0 +1,227 @@
+
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+
+#include "util.h"
+
+#define NLINES 256
+#define NCOLS 800
+
+char **buff;
+
+int obackspace, onotabs, ohalfline, oescape;
+unsigned nline, ncol, nchar, nspaces, maxline, bs;
+size_t pagsize = NLINES;
+
+static void
+usage(void)
+{
+	enprintf(2, "usage: %s [-p][-l num][-b][-f][-x]\n", argv0);
+}
+
+static void
+flush(void)
+{
+	int c;
+	unsigned i, j;
+
+	for (i = 0; i < maxline; ++i) {
+		for (j = 0; j < NCOLS && (c = buff[i][j]) != '\0'; ++j)
+			putchar(c);
+		putchar('\n');
+	}
+	bs = nchar = nline = ncol = 0;
+}
+
+static void
+forward(unsigned n)
+{
+	unsigned lim;
+
+	for (lim = ncol + n; ncol != lim && nchar < NCOLS-1; ++nchar) {
+		switch (buff[nline][nchar]) {
+		case '\b':
+			--ncol;
+			break;
+		case '\0':
+			buff[nline][nchar] = ' ';
+			/* FALLTHROUGH */
+		default:
+			++ncol;
+			break;
+		}
+	}
+}
+
+static void
+linefeed(int up, int rcarriage)
+{
+	unsigned oncol = ncol;
+
+	nspaces = 0;
+	if (up > 0) {
+		if (nline == pagsize-1) {
+			flush();
+		}  else {
+			if (++nline > maxline)
+				maxline = nline;
+		}
+	} else {
+		if (nline > 0)
+			--nline;
+	}
+	bs = 0;
+	if (rcarriage) {
+		forward(oncol);
+		 nchar = ncol = 0;
+	}
+}
+
+static void
+newchar(int c)
+{
+	char *cp;
+
+	forward(nspaces);
+	nspaces = 0;
+
+	switch (c) {
+	case ' ':
+		forward(1);
+		break;
+	case '\r':
+		nchar = ncol = 0;
+		break;
+	case '\t':
+		forward(8 - ncol%8);
+		break;
+	case '\b':
+		if (ncol > 0)
+			--ncol;
+		if (nchar > 0)
+			--nchar;
+		bs = 1;
+		break;
+	default:
+		cp = &buff[nline][nchar];
+		if (*cp != '\0' && *cp != ' ' && bs && !obackspace) {
+			if (nchar != NCOLS-3) {
+				memmove(cp + 3, cp + 1, NCOLS - nchar - 2);
+				cp[1] = '\b';
+				nchar += 2;
+			}
+		}
+		if (nchar != NCOLS-1) {
+			for (cp = buff[nline]; cp < &buff[nline][nchar]; ++cp) {
+				if (*cp == '\0')
+					*cp = ' ';
+			}
+			buff[nline][nchar++] = c;
+			++ncol;
+		}
+		bs = 0;
+	}
+}
+
+static void
+col(void)
+{
+	int c;
+
+	while ((c = getchar()) != EOF) {
+		switch (c) {
+		case '\x1b':
+			switch (c = getchar()) {
+			case '8': /* reverse half-line-feed */
+			case '7': /* reverse line-feed */
+				linefeed(-1, 0);
+				continue;
+			case '9':  /* forward half-line-feed */
+				if (ohalfline)
+					break;
+				linefeed(1, 0);
+				continue;
+			}
+			if (!oescape)
+				continue;
+			newchar('\x1b');
+			if (c != EOF)
+				newchar(c);			
+			break;
+		case '\v':
+			linefeed(-1, 0);
+			break;
+		case ' ':
+			if (!onotabs) {
+				if (++nspaces != 8)
+					continue;
+				c = '\t';
+				nspaces = 0;
+			}
+			/* FALLTHROUGH */
+		case '\r':
+		case '\b':
+		case '\t':
+			newchar(c);
+			break;
+		case '\n':
+			linefeed(1, 1);
+			break;
+		default:
+			if (!iscntrl(c))
+				newchar(c);
+			break;
+		}
+	}
+}
+
+static void
+allocbuf(void)
+{
+	char **bp;
+
+	buff = emalloc(sizeof(*buff) * pagsize);
+	for (bp = buff; bp < &buff[pagsize]; ++bp)
+		*bp = emalloc(NCOLS);	
+}
+
+int
+main(int argc, char *argv[])
+{
+	ARGBEGIN {
+	case 'b':
+		obackspace = 1;
+		break;
+	case 'f':
+		ohalfline = 1;
+		break;
+	case 'l':
+		pagsize = estrtonum(EARGF(usage()), 0, SIZE_MAX);
+		break;
+	case 'p':
+		oescape = 1;
+		break;
+	case 'x':
+		onotabs = 1;
+		break;
+	default:
+		usage();
+	} ARGEND;
+
+	if (argc > 0)
+		usage();
+
+	allocbuf();
+	col();
+	flush();
+
+	if (ferror(stdin))
+		enprintf(1, "error reading input");
+	if (ferror(stdout))
+		enprintf(2, "error writing output");
+
+	return 0;
+}