native_client_sdk/src/libraries/nacl_io/syscalls/realpath.c

   1 /* Copyright 2013 The Chromium Authors. All rights reserved.
   2  * Use of this source code is governed by a BSD-style license that can be
   3  * found in the LICENSE file. */
   4
   5 #include <assert.h>
   6 #include <stdlib.h>
   7 #include <errno.h>
   8 #include <limits.h>
   9 #include <stdlib.h>
  10 #include <string.h>
  11 #include <sys/stat.h>
  12 #include <unistd.h>
  13
  14 #include "sdk_util/macros.h"
  15
  16 EXTERN_C_BEGIN
  17
  18 #if defined(__native_client__)
  19
  20 // TODO(binji): glibc has realpath, but it fails for all tests. Investigate.
  21
  22 char* realpath(const char* path, char* resolved_path) {
  23   if (path == NULL) {
  24     errno = EINVAL;
  25     return NULL;
  26   }
  27
  28   int needs_free = 0;
  29   if (resolved_path == NULL) {
  30     resolved_path = (char*)malloc(PATH_MAX);
  31     needs_free = 1;
  32   }
  33
  34   struct stat statbuf;
  35   const char* in = path;
  36   char* out = resolved_path;
  37   char* out_end = resolved_path + PATH_MAX - 1;
  38   int done = 0;
  39
  40   *out = 0;
  41
  42   if (*in == '/') {
  43     // Absolute path.
  44     strcat(out, "/");
  45     in++;
  46     out++;
  47   } else {
  48     // Relative path.
  49     if (getcwd(out, out_end - out) == NULL)
  50       goto fail;
  51
  52     out += strlen(out);
  53   }
  54
  55   if (stat(resolved_path, &statbuf) != 0)
  56     goto fail;
  57
  58   while (!done) {
  59     const char* next_slash = strchr(in, '/');
  60     size_t namelen;
  61     const char* next_in;
  62     if (next_slash) {
  63       namelen = next_slash - in;
  64       next_in = next_slash + 1;
  65     } else {
  66       namelen = strlen(in);
  67       next_in = in + namelen;  // Move to the '\0'
  68       done = 1;
  69     }
  70
  71     if (namelen == 0) {
  72       // Empty name, do nothing.
  73     } else if (namelen == 1 && strncmp(in, ".", 1) == 0) {
  74       // Current directory, do nothing.
  75     } else if (namelen == 2 && strncmp(in, "..", 2) == 0) {
  76       // Parent directory, find previous slash in resolved_path.
  77       char* prev_slash = strrchr(resolved_path, '/');
  78       assert(prev_slash != NULL);
  79
  80       out = prev_slash;
  81       if (prev_slash == resolved_path) {
  82         // Moved to the root. Keep the slash.
  83         ++out;
  84       }
  85
  86       *out = 0;
  87     } else {
  88       // Append a slash if not at root.
  89       if (out != resolved_path + 1) {
  90         if (out + 1 > out_end) {
  91           errno = ENAMETOOLONG;
  92           goto fail;
  93         }
  94
  95         strncat(out, "/", namelen);
  96         out++;
  97       }
  98
  99       if (out + namelen > out_end) {
 100         errno = ENAMETOOLONG;
 101         goto fail;
 102       }
 103
 104       strncat(out, in, namelen);
 105       out += namelen;
 106     }
 107
 108     in = next_in;
 109
 110     if (stat(resolved_path, &statbuf) != 0)
 111       goto fail;
 112
 113     // If there is more to the path, then the current path must be a directory.
 114     if (!done && !S_ISDIR(statbuf.st_mode)) {
 115       errno = ENOTDIR;
 116       goto fail;
 117     }
 118   }
 119
 120   return resolved_path;
 121
 122 fail:
 123   if (needs_free) {
 124     free(resolved_path);
 125   }
 126   return NULL;
 127 }
 128
 129 EXTERN_C_END
 130
 131 #endif  // defined(__native_client__)