patch_cmds/patch/backupfile.c

   1 /*      $OpenBSD: backupfile.c,v 1.20 2009/10/27 23:59:41 deraadt Exp $ */
   2
   3 /*
   4  * backupfile.c -- make Emacs style backup file names Copyright (C) 1990 Free
   5  * Software Foundation, Inc.
   6  *
   7  * This program is free software; you can redistribute it and/or modify it
   8  * without restriction.
   9  *
  10  * This program is distributed in the hope that it will be useful, but WITHOUT
  11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12  * FITNESS FOR A PARTICULAR PURPOSE.
  13  */
  14
  15 /*
  16  * David MacKenzie <djm@ai.mit.edu>. Some algorithms adapted from GNU Emacs.
  17  */
  18
  19 #include <ctype.h>
  20 #include <dirent.h>
  21 #include <libgen.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <unistd.h>
  26
  27 #include "backupfile.h"
  28
  29
  30 #define ISDIGIT(c) (isascii (c) && isdigit (c))
  31
  32 /* Which type of backup file names are generated. */
  33 enum backup_type backup_type = none;
  34
  35 /*
  36  * The extension added to file names to produce a simple (as opposed to
  37  * numbered) backup file name.
  38  */
  39 char            *simple_backup_suffix = "~";
  40
  41 static char     *concat(const char *, const char *);
  42 static char     *make_version_name(const char *, int);
  43 static int      max_backup_version(const char *, const char *);
  44 static int      version_number(const char *, const char *, size_t);
  45 static int      argmatch(const char *, const char **);
  46 static void     invalid_arg(const char *, const char *, int);
  47
  48 /*
  49  * Return the name of the new backup file for file FILE, allocated with
  50  * malloc.  Return 0 if out of memory. FILE must not end with a '/' unless it
  51  * is the root directory. Do not call this function if backup_type == none.
  52  */
  53 char *
  54 find_backup_file_name(const char *file)
  55 {
  56         char    *dir, *base_versions;
  57         int     highest_backup;
  58
  59         if (backup_type == simple)
  60                 return concat(file, simple_backup_suffix);
  61         base_versions = concat(basename((char *)file), ".~");
  62         if (base_versions == NULL)
  63                 return NULL;
  64         dir = dirname((char *)file);
  65         if (dir == NULL) {
  66                 free(base_versions);
  67                 return NULL;
  68         }
  69         highest_backup = max_backup_version(base_versions, dir);
  70         free(base_versions);
  71         if (backup_type == numbered_existing && highest_backup == 0)
  72                 return concat(file, simple_backup_suffix);
  73         return make_version_name(file, highest_backup + 1);
  74 }
  75
  76 /*
  77  * Return the number of the highest-numbered backup file for file FILE in
  78  * directory DIR.  If there are no numbered backups of FILE in DIR, or an
  79  * error occurs reading DIR, return 0. FILE should already have ".~" appended
  80  * to it.
  81  */
  82 static int
  83 max_backup_version(const char *file, const char *dir)
  84 {
  85         DIR     *dirp;
  86         struct dirent   *dp;
  87         int     highest_version, this_version;
  88         size_t  file_name_length;
  89
  90         dirp = opendir(dir);
  91         if (dirp == NULL)
  92                 return 0;
  93
  94         highest_version = 0;
  95         file_name_length = strlen(file);
  96
  97         while ((dp = readdir(dirp)) != NULL) {
  98                 if (dp->d_namlen <= file_name_length)
  99                         continue;
 100
 101                 this_version = version_number(file, dp->d_name, file_name_length);
 102                 if (this_version > highest_version)
 103                         highest_version = this_version;
 104         }
 105         closedir(dirp);
 106         return highest_version;
 107 }
 108
 109 /*
 110  * Return a string, allocated with malloc, containing "FILE.~VERSION~".
 111  * Return 0 if out of memory.
 112  */
 113 static char *
 114 make_version_name(const char *file, int version)
 115 {
 116         char    *backup_name;
 117
 118         if (asprintf(&backup_name, "%s.~%d~", file, version) == -1)
 119                 return NULL;
 120         return backup_name;
 121 }
 122
 123 /*
 124  * If BACKUP is a numbered backup of BASE, return its version number;
 125  * otherwise return 0.  BASE_LENGTH is the length of BASE. BASE should
 126  * already have ".~" appended to it.
 127  */
 128 static int
 129 version_number(const char *base, const char *backup, size_t base_length)
 130 {
 131         int             version;
 132         const char      *p;
 133
 134         version = 0;
 135         if (!strncmp(base, backup, base_length) && ISDIGIT(backup[base_length])) {
 136                 for (p = &backup[base_length]; ISDIGIT(*p); ++p)
 137                         version = version * 10 + *p - '0';
 138                 if (p[0] != '~' || p[1])
 139                         version = 0;
 140         }
 141         return version;
 142 }
 143
 144 /*
 145  * Return the newly-allocated concatenation of STR1 and STR2. If out of
 146  * memory, return 0.
 147  */
 148 static char  *
 149 concat(const char *str1, const char *str2)
 150 {
 151         char    *newstr;
 152
 153         if (asprintf(&newstr, "%s%s", str1, str2) == -1)
 154                 return NULL;
 155         return newstr;
 156 }
 157
 158 /*
 159  * If ARG is an unambiguous match for an element of the null-terminated array
 160  * OPTLIST, return the index in OPTLIST of the matched element, else -1 if it
 161  * does not match any element or -2 if it is ambiguous (is a prefix of more
 162  * than one element).
 163  */
 164 static int
 165 argmatch(const char *arg, const char **optlist)
 166 {
 167         int     i;      /* Temporary index in OPTLIST. */
 168         size_t  arglen; /* Length of ARG. */
 169         int     matchind = -1;  /* Index of first nonexact match. */
 170         int     ambiguous = 0;  /* If nonzero, multiple nonexact match(es). */
 171
 172         arglen = strlen(arg);
 173
 174         /* Test all elements for either exact match or abbreviated matches.  */
 175         for (i = 0; optlist[i]; i++) {
 176                 if (!strncmp(optlist[i], arg, arglen)) {
 177                         if (strlen(optlist[i]) == arglen)
 178                                 /* Exact match found.  */
 179                                 return i;
 180                         else if (matchind == -1)
 181                                 /* First nonexact match found.  */
 182                                 matchind = i;
 183                         else
 184                                 /* Second nonexact match found.  */
 185                                 ambiguous = 1;
 186                 }
 187         }
 188         if (ambiguous)
 189                 return -2;
 190         else
 191                 return matchind;
 192 }
 193
 194 /*
 195  * Error reporting for argmatch. KIND is a description of the type of entity
 196  * that was being matched. VALUE is the invalid value that was given. PROBLEM
 197  * is the return value from argmatch.
 198  */
 199 static void
 200 invalid_arg(const char *kind, const char *value, int problem)
 201 {
 202         fprintf(stderr, "patch: ");
 203         if (problem == -1)
 204                 fprintf(stderr, "invalid");
 205         else                    /* Assume -2. */
 206                 fprintf(stderr, "ambiguous");
 207         fprintf(stderr, " %s `%s'\n", kind, value);
 208 }
 209
 210 static const char *backup_args[] = {
 211         "never", "simple", "nil", "existing", "t", "numbered", 0
 212 };
 213
 214 static enum backup_type backup_types[] = {
 215         simple, simple, numbered_existing,
 216         numbered_existing, numbered, numbered
 217 };
 218
 219 /*
 220  * Return the type of backup indicated by VERSION. Unique abbreviations are
 221  * accepted.
 222  */
 223 enum backup_type
 224 get_version(const char *version)
 225 {
 226         int     i;
 227
 228         if (version == NULL || *version == '\0')
 229                 return numbered_existing;
 230         i = argmatch(version, backup_args);
 231         if (i >= 0)
 232                 return backup_types[i];
 233         invalid_arg("version control type", version, i);
 234         exit(2);
 235 }