src/nibswap.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause
   3  *
   4  * Copyright (c) 2022 Alessio Chiapperini
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  25  * SUCH DAMAGE.
  26  */
  27
  28 #ifndef _POSIX_C_SOURCE
  29 #  define _POSIX_C_SOURCE 200112L
  30 #elif _POSIX_C_SOURCE < 200112L
  31 #  error incompatible _POSIX_C_SOURCE level
  32 #endif
  33
  34 #include <limits.h>
  35 #include <stdio.h>
  36 #include <stdlib.h>
  37 #include <string.h>
  38 #include <unistd.h>
  39
  40 static void
  41 usage(void)
  42 {
  43         (void)fprintf(stderr, "usage: nibswap [-h] [file ...]\n");
  44         exit(1);
  45 }
  46
  47 static int
  48 nibswap(const char *src)
  49 {
  50         char line[LINE_MAX] = {0};
  51         FILE *ifile;
  52         size_t i, len;
  53         int ret;
  54
  55         ret = 0;
  56         ifile = stdin;
  57         if (src[0] != '-' || src[1] != '\0') {
  58                 ifile = fopen(src, "r");
  59                 if (ifile == 0) {
  60                         ret = 1;
  61                         perror("nibswap");
  62                         goto open_err;
  63                 }
  64         }
  65
  66         while (fgets(line, LINE_MAX, ifile) != 0) {
  67                 line[strcspn(line, "\n")] = 0;
  68
  69                 len = strlen(line);
  70                 if (len % 2 != 0) {
  71                         ret = 1;
  72                         (void)fprintf(stderr, "nibswap: the length of the "
  73                             "string '%s' must be even\n", line);
  74                         break;
  75                 }
  76
  77                 for (i = 0; i+1 < len; i+=2) {
  78                         char tmp = 0;
  79                         tmp = line[i];
  80                         line[i] = line[i+1];
  81                         line[i+1] = tmp;
  82                 }
  83                 (void)printf("%s\n", line);
  84         }
  85
  86         (void)fclose(ifile);
  87 open_err:
  88         return (ret);
  89 }
  90
  91 int
  92 main(int argc, char *argv[])
  93 {
  94         char *def[] = { "-" };
  95         int opt;
  96
  97         while ((opt = getopt(argc, argv, "hu")) != -1) {
  98                 switch (opt) {
  99                 case 'h':
 100                         usage();
 101                         break;
 102                 case '?':
 103                         /* FALLTHROUGH */
 104                 default:
 105                         usage();
 106                 }
 107         }
 108
 109         argc -= optind;
 110         argv += optind;
 111
 112         if (argc == 0) {
 113                 argc = 1;
 114                 argv = def;
 115         }
 116
 117         for (int i = 0; i < argc; i++) {
 118                 if (nibswap(argv[i]) > 0) {
 119                         return (1);
 120                 }
 121         }
 122
 123         return (0);
 124 }
 125