dart:io | Add Link.targetSync on all platforms.

runtime/bin/file_linux.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
 #if defined(TARGET_OS_LINUX)
 
 #include "bin/file.h"
 
 #include <errno.h>  // NOLINT
@@ skipping 175 matching lines @@
 
 time_t File::LastModified(const char* name) {
   struct stat st;
   if (TEMP_FAILURE_RETRY(stat(name, &st)) == 0) {
     return st.st_mtime;
   }
   return -1;
 }
 
 
+char* File::LinkTarget(const char* pathname) {
+  struct stat link_stats;
+  if (lstat(pathname, &link_stats) != 0) return NULL;
+  // TODO(whesse): return a better error than LinkIOException(OSError) here.
+  if (!S_ISLNK(link_stats.st_mode)) return NULL;
+  size_t target_size = link_stats.st_size;
+  char* target_name = reinterpret_cast<char*>(malloc(target_size + 1));
+  size_t read_size = readlink(pathname, target_name, target_size + 1);
+  if (read_size != target_size) {
+    free(target_name);
+    return NULL;
+  }
+  target_name[target_size] = '\0';
+  return target_name;
+}
+
+
 bool File::IsAbsolutePath(const char* pathname) {
   return (pathname != NULL && pathname[0] == '/');
 }
 
 
 char* File::GetCanonicalPath(const char* pathname) {
   char* abs_path = NULL;
   if (pathname != NULL) {
     do {
       abs_path = realpath(pathname, NULL);
@@ skipping 57 matching lines @@
     stat_success = TEMP_FAILURE_RETRY(lstat(pathname, &entry_info));
   }
   if (stat_success == -1) return File::kDoesNotExist;
   if (S_ISDIR(entry_info.st_mode)) return File::kIsDirectory;
   if (S_ISREG(entry_info.st_mode)) return File::kIsFile;
   if (S_ISLNK(entry_info.st_mode)) return File::kIsLink;
   return File::kDoesNotExist;
 }
 
 #endif  // defined(TARGET_OS_LINUX)