abspath.c

   1 #include "cache.h"
   2
   3 /*
   4  * Do not use this for inspecting *tracked* content.  When path is a
   5  * symlink to a directory, we do not want to say it is a directory when
   6  * dealing with tracked content in the working tree.
   7  */
   8 int is_directory(const char *path)
   9 {
  10         struct stat st;
  11         return (!stat(path, &st) && S_ISDIR(st.st_mode));
  12 }
  13
  14 /* We allow "recursive" symbolic links. Only within reason, though. */
  15 #define MAXDEPTH 5
  16
  17 /*
  18  * Return the real path (i.e., absolute path, with symlinks resolved
  19  * and extra slashes removed) equivalent to the specified path.  (If
  20  * you want an absolute path but don't mind links, use
  21  * absolute_path().)  The return value is a pointer to a static
  22  * buffer.
  23  *
  24  * The input and all intermediate paths must be shorter than MAX_PATH.
  25  * The directory part of path (i.e., everything up to the last
  26  * dir_sep) must denote a valid, existing directory, but the last
  27  * component need not exist.  If die_on_error is set, then die with an
  28  * informative error message if there is a problem.  Otherwise, return
  29  * NULL on errors (without generating any output).
  30  *
  31  * If path is our buffer, then return path, as it's already what the
  32  * user wants.
  33  */
  34 static const char *real_path_internal(const char *path, int die_on_error)
  35 {
  36         static char bufs[2][PATH_MAX + 1], *buf = bufs[0], *next_buf = bufs[1];
  37         char *retval = NULL;
  38
  39         /*
  40          * If we have to temporarily chdir(), store the original CWD
  41          * here so that we can chdir() back to it at the end of the
  42          * function:
  43          */
  44         char cwd[1024] = "";
  45
  46         int buf_index = 1;
  47
  48         int depth = MAXDEPTH;
  49         char *last_elem = NULL;
  50         struct stat st;
  51
  52         /* We've already done it */
  53         if (path == buf || path == next_buf)
  54                 return path;
  55
  56         if (!*path) {
  57                 if (die_on_error)
  58                         die("The empty string is not a valid path");
  59                 else
  60                         goto error_out;
  61         }
  62
  63         if (strlcpy(buf, path, PATH_MAX) >= PATH_MAX) {
  64                 if (die_on_error)
  65                         die("Too long path: %.*s", 60, path);
  66                 else
  67                         goto error_out;
  68         }
  69
  70         while (depth--) {
  71                 if (!is_directory(buf)) {
  72                         char *last_slash = find_last_dir_sep(buf);
  73                         if (last_slash) {
  74                                 last_elem = xstrdup(last_slash + 1);
  75                                 last_slash[1] = '\0';
  76                         } else {
  77                                 last_elem = xstrdup(buf);
  78                                 *buf = '\0';
  79                         }
  80                 }
  81
  82                 if (*buf) {
  83                         if (!*cwd && !getcwd(cwd, sizeof(cwd))) {
  84                                 if (die_on_error)
  85                                         die_errno("Could not get current working directory");
  86                                 else
  87                                         goto error_out;
  88                         }
  89
  90                         if (chdir(buf)) {
  91                                 if (die_on_error)
  92                                         die_errno("Could not switch to '%s'", buf);
  93                                 else
  94                                         goto error_out;
  95                         }
  96                 }
  97                 if (!getcwd(buf, PATH_MAX)) {
  98                         if (die_on_error)
  99                                 die_errno("Could not get current working directory");
 100                         else
 101                                 goto error_out;
 102                 }
 103
 104                 if (last_elem) {
 105                         size_t len = strlen(buf);
 106                         if (len + strlen(last_elem) + 2 > PATH_MAX) {
 107                                 if (die_on_error)
 108                                         die("Too long path name: '%s/%s'",
 109                                             buf, last_elem);
 110                                 else
 111                                         goto error_out;
 112                         }
 113                         if (len && !is_dir_sep(buf[len-1]))
 114                                 buf[len++] = '/';
 115                         strcpy(buf + len, last_elem);
 116                         free(last_elem);
 117                         last_elem = NULL;
 118                 }
 119
 120                 if (!lstat(buf, &st) && S_ISLNK(st.st_mode)) {
 121                         ssize_t len = readlink(buf, next_buf, PATH_MAX);
 122                         if (len < 0) {
 123                                 if (die_on_error)
 124                                         die_errno("Invalid symlink '%s'", buf);
 125                                 else
 126                                         goto error_out;
 127                         }
 128                         if (PATH_MAX <= len) {
 129                                 if (die_on_error)
 130                                         die("symbolic link too long: %s", buf);
 131                                 else
 132                                         goto error_out;
 133                         }
 134                         next_buf[len] = '\0';
 135                         buf = next_buf;
 136                         buf_index = 1 - buf_index;
 137                         next_buf = bufs[buf_index];
 138                 } else
 139                         break;
 140         }
 141
 142         retval = buf;
 143 error_out:
 144         free(last_elem);
 145         if (*cwd && chdir(cwd))
 146                 die_errno ("Could not change back to '%s'", cwd);
 147
 148         return retval;
 149 }
 150
 151 const char *real_path(const char *path)
 152 {
 153         return real_path_internal(path, 1);
 154 }
 155
 156 const char *real_path_if_valid(const char *path)
 157 {
 158         return real_path_internal(path, 0);
 159 }
 160
 161 static const char *get_pwd_cwd(void)
 162 {
 163         static char cwd[PATH_MAX + 1];
 164         char *pwd;
 165         struct stat cwd_stat, pwd_stat;
 166         if (getcwd(cwd, PATH_MAX) == NULL)
 167                 return NULL;
 168         pwd = getenv("PWD");
 169         if (pwd && strcmp(pwd, cwd)) {
 170                 stat(cwd, &cwd_stat);
 171                 if ((cwd_stat.st_dev || cwd_stat.st_ino) &&
 172                     !stat(pwd, &pwd_stat) &&
 173                     pwd_stat.st_dev == cwd_stat.st_dev &&
 174                     pwd_stat.st_ino == cwd_stat.st_ino) {
 175                         strlcpy(cwd, pwd, PATH_MAX);
 176                 }
 177         }
 178         return cwd;
 179 }
 180
 181 /*
 182  * Use this to get an absolute path from a relative one. If you want
 183  * to resolve links, you should use real_path.
 184  *
 185  * If the path is already absolute, then return path. As the user is
 186  * never meant to free the return value, we're safe.
 187  */
 188 const char *absolute_path(const char *path)
 189 {
 190         static char buf[PATH_MAX + 1];
 191
 192         if (!*path) {
 193                 die("The empty string is not a valid path");
 194         } else if (is_absolute_path(path)) {
 195                 if (strlcpy(buf, path, PATH_MAX) >= PATH_MAX)
 196                         die("Too long path: %.*s", 60, path);
 197         } else {
 198                 size_t len;
 199                 const char *fmt;
 200                 const char *cwd = get_pwd_cwd();
 201                 if (!cwd)
 202                         die_errno("Cannot determine the current working directory");
 203                 len = strlen(cwd);
 204                 fmt = (len > 0 && is_dir_sep(cwd[len-1])) ? "%s%s" : "%s/%s";
 205                 if (snprintf(buf, PATH_MAX, fmt, cwd, path) >= PATH_MAX)
 206                         die("Too long path: %.*s", 60, path);
 207         }
 208         return buf;
 209 }
 210
 211 /*
 212  * Unlike prefix_path, this should be used if the named file does
 213  * not have to interact with index entry; i.e. name of a random file
 214  * on the filesystem.
 215  */
 216 const char *prefix_filename(const char *pfx, int pfx_len, const char *arg)
 217 {
 218         static char path[PATH_MAX];
 219 #ifndef WIN32
 220         if (!pfx_len || is_absolute_path(arg))
 221                 return arg;
 222         memcpy(path, pfx, pfx_len);
 223         strcpy(path + pfx_len, arg);
 224 #else
 225         char *p;
 226         /* don't add prefix to absolute paths, but still replace '\' by '/' */
 227         if (is_absolute_path(arg))
 228                 pfx_len = 0;
 229         else if (pfx_len)
 230                 memcpy(path, pfx, pfx_len);
 231         strcpy(path + pfx_len, arg);
 232         for (p = path + pfx_len; *p; p++)
 233                 if (*p == '\\')
 234                         *p = '/';
 235 #endif
 236         return path;
 237 }