fixwhite.c revision 299826 
1/*-
2 * Copyright (c) 2012 Ed Schouten <ed@FreeBSD.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27#include <sys/cdefs.h>
28__FBSDID("$FreeBSD: stable/10/tools/tools/fixwhite/fixwhite.c 299826 2016-05-15 03:15:36Z pfg $");
29
30#include <ctype.h>
31#include <stdbool.h>
32#include <stdio.h>
33#include <stdlib.h>
34
35static char *queue = NULL;
36static size_t queuelen = 0, queuesize = 0;
37static off_t column = 0;
38
39static void
40savebyte(char c)
41{
42
43	if (queuelen >= queuesize) {
44		queuesize += 128;
45		queue = realloc(queue, queuesize);
46		if (queue == NULL) {
47			perror("malloc");
48			exit(1);
49		}
50	}
51	queue[queuelen++] = c;
52
53	switch (c) {
54	case '\n':
55		column = 0;
56		break;
57	case ' ':
58		column++;
59		break;
60	case '\t':
61		column = (column / 8 + 1) * 8;
62		break;
63	}
64}
65
66static bool
67peekbyte(size_t back, char c)
68{
69
70	return (queuelen >= back && queue[queuelen - back] == c);
71}
72
73static void
74savewhite(char c, bool leading)
75{
76	off_t ncolumn;
77
78	switch (c) {
79	case '\n':
80		if (leading) {
81			/* Remove empty lines before input. */
82			queuelen = 0;
83			column = 0;
84		} else {
85			/* Remove trailing whitespace. */
86			while (peekbyte(1, ' ') || peekbyte(1, '\t'))
87				queuelen--;
88			/* Remove redundant empty lines. */
89			if (peekbyte(2, '\n') && peekbyte(1, '\n'))
90				return;
91			savebyte('\n');
92		}
93		break;
94	case ' ':
95		savebyte(' ');
96		break;
97	case '\t':
98		/* Convert preceding spaces to tabs. */
99		ncolumn = (column / 8 + 1) * 8;
100		while (peekbyte(1, ' ')) {
101			queuelen--;
102			column--;
103		}
104		while (column < ncolumn)
105			savebyte('\t');
106		break;
107	}
108}
109
110static void
111printwhite(void)
112{
113	off_t i;
114
115	/* Merge spaces at the start of a sentence to tabs if possible. */
116	if ((column % 8) == 0) {
117		for (i = 0; i < column; i++)
118			if (!peekbyte(i + 1, ' '))
119				break;
120		if (i == column) {
121			queuelen -= column;
122			for (i = 0; i < column; i += 8)
123				queue[queuelen++] = '\t';
124		}
125	}
126
127	if (fwrite(queue, 1, queuelen, stdout) != queuelen) {
128		perror("write");
129		exit(1);
130	}
131	queuelen = 0;
132}
133
134static char
135readchar(void)
136{
137	int c;
138
139	c = getchar();
140	if (c == EOF && ferror(stdin)) {
141		perror("read");
142		exit(1);
143	}
144	return (c);
145}
146
147static void
148writechar(char c)
149{
150
151	if (putchar(c) == EOF) {
152		perror("write");
153		exit(1);
154	}
155	/* XXX: Multi-byte characters. */
156	column++;
157}
158
159int
160main(void)
161{
162	int c;
163	bool leading = true;
164
165	while ((c = readchar()) != EOF) {
166		if (isspace(c))
167			/* Save whitespace. */
168			savewhite(c, leading);
169		else {
170			/* Reprint whitespace and print regular character. */
171			printwhite();
172			writechar(c);
173			leading = false;
174		}
175	}
176	/* Terminate non-empty files with a newline. */
177	if (!leading)
178		writechar('\n');
179	return (0);
180}
181