abspath.c

   1 #include "git-compat-util.h"
   2 #include "abspath.h"
   3 #include "strbuf.h"
   4
   5 /*
   6  * Do not use this for inspecting *tracked* content.  When path is a
   7  * symlink to a directory, we do not want to say it is a directory when
   8  * dealing with tracked content in the working tree.
   9  */
  10 int is_directory(const char *path)
  11 {
  12         struct stat st;
  13         return (!stat(path, &st) && S_ISDIR(st.st_mode));
  14 }
  15
  16 /* removes the last path component from 'path' except if 'path' is root */
  17 static void strip_last_component(struct strbuf *path)
  18 {
  19         size_t offset = offset_1st_component(path->buf);
  20         size_t len = path->len;
  21
  22         /* Find start of the last component */
  23         while (offset < len && !is_dir_sep(path->buf[len - 1]))
  24                 len--;
  25         /* Skip sequences of multiple path-separators */
  26         while (offset < len && is_dir_sep(path->buf[len - 1]))
  27                 len--;
  28
  29         strbuf_setlen(path, len);
  30 }
  31
  32 /* get (and remove) the next component in 'remaining' and place it in 'next' */
  33 static void get_next_component(struct strbuf *next, struct strbuf *remaining)
  34 {
  35         char *start = NULL;
  36         char *end = NULL;
  37
  38         strbuf_reset(next);
  39
  40         /* look for the next component */
  41         /* Skip sequences of multiple path-separators */
  42         for (start = remaining->buf; is_dir_sep(*start); start++)
  43                 ; /* nothing */
  44         /* Find end of the path component */
  45         for (end = start; *end && !is_dir_sep(*end); end++)
  46                 ; /* nothing */
  47
  48         strbuf_add(next, start, end - start);
  49         /* remove the component from 'remaining' */
  50         strbuf_remove(remaining, 0, end - remaining->buf);
  51 }
  52
  53 /* copies root part from remaining to resolved, canonicalizing it on the way */
  54 static void get_root_part(struct strbuf *resolved, struct strbuf *remaining)
  55 {
  56         int offset = offset_1st_component(remaining->buf);
  57
  58         strbuf_reset(resolved);
  59         strbuf_add(resolved, remaining->buf, offset);
  60 #ifdef GIT_WINDOWS_NATIVE
  61         convert_slashes(resolved->buf);
  62 #endif
  63         strbuf_remove(remaining, 0, offset);
  64 }
  65
  66 /* We allow "recursive" symbolic links. Only within reason, though. */
  67 #ifndef MAXSYMLINKS
  68 #define MAXSYMLINKS 32
  69 #endif
  70
  71 /*
  72  * If set, any number of trailing components may be missing; otherwise, only one
  73  * may be.
  74  */
  75 #define REALPATH_MANY_MISSING (1 << 0)
  76 /* Should we die if there's an error? */
  77 #define REALPATH_DIE_ON_ERROR (1 << 1)
  78
  79 static char *strbuf_realpath_1(struct strbuf *resolved, const char *path,
  80                                int flags)
  81 {
  82         struct strbuf remaining = STRBUF_INIT;
  83         struct strbuf next = STRBUF_INIT;
  84         struct strbuf symlink = STRBUF_INIT;
  85         char *retval = NULL;
  86         int num_symlinks = 0;
  87         struct stat st;
  88
  89         if (!*path) {
  90                 if (flags & REALPATH_DIE_ON_ERROR)
  91                         die("The empty string is not a valid path");
  92                 else
  93                         goto error_out;
  94         }
  95
  96         strbuf_addstr(&remaining, path);
  97         get_root_part(resolved, &remaining);
  98
  99         if (!resolved->len) {
 100                 /* relative path; can use CWD as the initial resolved path */
 101                 if (strbuf_getcwd(resolved)) {
 102                         if (flags & REALPATH_DIE_ON_ERROR)
 103                                 die_errno("unable to get current working directory");
 104                         else
 105                                 goto error_out;
 106                 }
 107         }
 108
 109         /* Iterate over the remaining path components */
 110         while (remaining.len > 0) {
 111                 get_next_component(&next, &remaining);
 112
 113                 if (next.len == 0) {
 114                         continue; /* empty component */
 115                 } else if (next.len == 1 && !strcmp(next.buf, ".")) {
 116                         continue; /* '.' component */
 117                 } else if (next.len == 2 && !strcmp(next.buf, "..")) {
 118                         /* '..' component; strip the last path component */
 119                         strip_last_component(resolved);
 120                         continue;
 121                 }
 122
 123                 /* append the next component and resolve resultant path */
 124                 if (!is_dir_sep(resolved->buf[resolved->len - 1]))
 125                         strbuf_addch(resolved, '/');
 126                 strbuf_addbuf(resolved, &next);
 127
 128                 if (lstat(resolved->buf, &st)) {
 129                         /* error out unless this was the last component */
 130                         if (errno != ENOENT ||
 131                            (!(flags & REALPATH_MANY_MISSING) && remaining.len)) {
 132                                 if (flags & REALPATH_DIE_ON_ERROR)
 133                                         die_errno("Invalid path '%s'",
 134                                                   resolved->buf);
 135                                 else
 136                                         goto error_out;
 137                         }
 138                 } else if (S_ISLNK(st.st_mode)) {
 139                         ssize_t len;
 140                         strbuf_reset(&symlink);
 141
 142                         if (num_symlinks++ > MAXSYMLINKS) {
 143                                 errno = ELOOP;
 144
 145                                 if (flags & REALPATH_DIE_ON_ERROR)
 146                                         die("More than %d nested symlinks "
 147                                             "on path '%s'", MAXSYMLINKS, path);
 148                                 else
 149                                         goto error_out;
 150                         }
 151
 152                         len = strbuf_readlink(&symlink, resolved->buf,
 153                                               st.st_size);
 154                         if (len < 0) {
 155                                 if (flags & REALPATH_DIE_ON_ERROR)
 156                                         die_errno("Invalid symlink '%s'",
 157                                                   resolved->buf);
 158                                 else
 159                                         goto error_out;
 160                         }
 161
 162                         if (is_absolute_path(symlink.buf)) {
 163                                 /* absolute symlink; set resolved to root */
 164                                 get_root_part(resolved, &symlink);
 165                         } else {
 166                                 /*
 167                                  * relative symlink
 168                                  * strip off the last component since it will
 169                                  * be replaced with the contents of the symlink
 170                                  */
 171                                 strip_last_component(resolved);
 172                         }
 173
 174                         /*
 175                          * if there are still remaining components to resolve
 176                          * then append them to symlink
 177                          */
 178                         if (remaining.len) {
 179                                 strbuf_addch(&symlink, '/');
 180                                 strbuf_addbuf(&symlink, &remaining);
 181                         }
 182
 183                         /*
 184                          * use the symlink as the remaining components that
 185                          * need to be resolved
 186                          */
 187                         strbuf_swap(&symlink, &remaining);
 188                 }
 189         }
 190
 191         retval = resolved->buf;
 192
 193 error_out:
 194         strbuf_release(&remaining);
 195         strbuf_release(&next);
 196         strbuf_release(&symlink);
 197
 198         if (!retval)
 199                 strbuf_reset(resolved);
 200
 201         return retval;
 202 }
 203
 204 /*
 205  * Return the real path (i.e., absolute path, with symlinks resolved
 206  * and extra slashes removed) equivalent to the specified path.  (If
 207  * you want an absolute path but don't mind links, use
 208  * absolute_path().)  Places the resolved realpath in the provided strbuf.
 209  *
 210  * The directory part of path (i.e., everything up to the last
 211  * dir_sep) must denote a valid, existing directory, but the last
 212  * component need not exist.  If die_on_error is set, then die with an
 213  * informative error message if there is a problem.  Otherwise, return
 214  * NULL on errors (without generating any output).
 215  */
 216 char *strbuf_realpath(struct strbuf *resolved, const char *path,
 217                       int die_on_error)
 218 {
 219         return strbuf_realpath_1(resolved, path,
 220                                  die_on_error ? REALPATH_DIE_ON_ERROR : 0);
 221 }
 222
 223 /*
 224  * Just like strbuf_realpath, but allows an arbitrary number of path
 225  * components to be missing.
 226  */
 227 char *strbuf_realpath_forgiving(struct strbuf *resolved, const char *path,
 228                                 int die_on_error)
 229 {
 230         return strbuf_realpath_1(resolved, path,
 231                                  ((die_on_error ? REALPATH_DIE_ON_ERROR : 0) |
 232                                   REALPATH_MANY_MISSING));
 233 }
 234
 235 char *real_pathdup(const char *path, int die_on_error)
 236 {
 237         struct strbuf realpath = STRBUF_INIT;
 238         char *retval = NULL;
 239
 240         if (strbuf_realpath(&realpath, path, die_on_error))
 241                 retval = strbuf_detach(&realpath, NULL);
 242
 243         strbuf_release(&realpath);
 244
 245         return retval;
 246 }
 247
 248 /*
 249  * Use this to get an absolute path from a relative one. If you want
 250  * to resolve links, you should use strbuf_realpath.
 251  */
 252 const char *absolute_path(const char *path)
 253 {
 254         static struct strbuf sb = STRBUF_INIT;
 255         strbuf_reset(&sb);
 256         strbuf_add_absolute_path(&sb, path);
 257         return sb.buf;
 258 }
 259
 260 char *absolute_pathdup(const char *path)
 261 {
 262         struct strbuf sb = STRBUF_INIT;
 263         strbuf_add_absolute_path(&sb, path);
 264         return strbuf_detach(&sb, NULL);
 265 }
 266
 267 char *prefix_filename(const char *pfx, const char *arg)
 268 {
 269         struct strbuf path = STRBUF_INIT;
 270         size_t pfx_len = pfx ? strlen(pfx) : 0;
 271
 272         if (!pfx_len)
 273                 ; /* nothing to prefix */
 274         else if (is_absolute_path(arg))
 275                 pfx_len = 0;
 276         else
 277                 strbuf_add(&path, pfx, pfx_len);
 278
 279         strbuf_addstr(&path, arg);
 280 #ifdef GIT_WINDOWS_NATIVE
 281         convert_slashes(path.buf + pfx_len);
 282 #endif
 283         return strbuf_detach(&path, NULL);
 284 }
 285
 286 char *prefix_filename_except_for_dash(const char *pfx, const char *arg)
 287 {
 288         if (!strcmp(arg, "-"))
 289                 return xstrdup(arg);
 290         return prefix_filename(pfx, arg);
 291 }