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("$FreeBSD$"); 29 30 #include <ctype.h> 31 #include <stdbool.h> 32 #include <stdio.h> 33 #include <stdlib.h> 34 35 static char *queue = NULL; 36 static size_t queuelen = 0, queuesize = 0; 37 static off_t column = 0; 38 39 static void 40 savebyte(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 66 static bool 67 peekbyte(size_t back, char c) 68 { 69 70 return (queuelen >= back && queue[queuelen - back] == c); 71 } 72 73 static void 74 savewhite(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 } 109 110 static void 111 printwhite(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 } 133 134 static char 135 readchar(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 } 146 147 static void 148 writechar(char c) 149 { 150 151 if (putchar(c) == EOF) { 152 perror("write"); 153 exit(1); 154 } 155 /* XXX: Multi-byte characters. */ 156 column++; 157 } 158 159 int 160 main(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