Add unexpand(1)

unexpand.c

@@ -0,0 +1,140 @@
+/* See LICENSE file for copyright and license details. */
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <wchar.h>
+#include "util.h"
+
+typedef struct {
+	FILE *fp;
+	const char *name;
+} Fdescr;
+
+static void unexpand(Fdescr *dsc);
+
+static bool aflag = false;
+static int tabsize = 8;
+
+static void
+usage(void)
+{
+	eprintf("usage: %s [-a] [-t n] [file ...]\n", argv0);
+}
+
+int
+main(int argc, char *argv[])
+{
+	Fdescr dsc;
+	FILE *fp;
+
+	ARGBEGIN {
+	case 't':
+		tabsize = estrtol(EARGF(usage()), 0);
+		if(tabsize <= 0)
+			eprintf("unexpand: invalid tabsize\n", argv[0]);
+		/* Fallthrough: -t implies -a */
+	case 'a':
+		aflag = true;
+		break;
+	default:
+		usage();
+	} ARGEND;
+
+	if (argc == 0) {
+		dsc.name = "<stdin>";
+		dsc.fp = stdin;
+		unexpand(&dsc);
+	} else {
+		for (; argc > 0; argc--, argv++) {
+			if (!(fp = fopen(*argv, "r"))) {
+				weprintf("fopen %s:", *argv);
+				continue;
+			}
+			dsc.name = *argv;
+			dsc.fp = fp;
+			unexpand(&dsc);
+			fclose(fp);
+		}
+	}
+
+	return EXIT_SUCCESS;
+}
+
+static wint_t
+in(Fdescr *f)
+{
+	wint_t c = fgetwc(f->fp);
+
+	if (c == WEOF && ferror(f->fp))
+		eprintf("'%s' read error:", f->name);
+
+	return c;
+}
+
+static void
+out(wint_t c)
+{
+	putwchar(c);
+	if (ferror(stdout))
+		eprintf("write error:");
+}
+
+static void
+unexpandspan(unsigned int n, unsigned int col)
+{
+	unsigned int off = (col-n) % tabsize;
+
+	if(n + off >= tabsize && n > 1)
+		n += off;
+
+	for(; n >= tabsize; n -= tabsize)
+		out('\t');
+	while(n--)
+		out(' ');
+}
+
+static void
+unexpand(Fdescr *dsc)
+{
+	unsigned int n = 0, col = 0;
+	bool bol = true;
+	wint_t c;
+
+	while ((c = in(dsc)) != EOF) {
+		switch (c) {
+		case ' ':
+			if (bol || aflag)
+				n++;
+			col++;
+			break;
+		case '\t':
+			if (bol || aflag)
+				n += tabsize - col % tabsize;
+			col += tabsize - col % tabsize;
+			break;
+		case '\b':
+			if (bol || aflag)
+				unexpandspan(n, col);
+			col -= (col > 0);
+			n = 0;
+			bol = false;
+			break;
+		case '\n':
+			if (bol || aflag)
+				unexpandspan(n, col);
+			n = col = 0;
+			bol = true;
+			break;
+		default:
+			if (bol || aflag)
+				unexpandspan(n, col);
+			n = 0;
+			col++;
+			bol = false;
+		}
+		if ((c != ' ' && c != '\t') || (!aflag && !bol))
+			out(c);
+	}
+	if (n > 0 && (bol || aflag))
+		unexpandspan(n, col);
+}