First step of porting VisitedLinkMaster to POSIX:

base/file_util.cc

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/file_util.h"
 
 #include <stdio.h>
 
 #include <fstream>
 
@@ skipping 258 matching lines @@
   *file_size = info.size;
   return true;
 }
 
 bool CloseFile(FILE* file) {
   if (file == NULL)
     return true;
   return fclose(file) == 0;
 }
 
+bool TruncateFile(FILE* file) {
+  if (file == NULL)
+    return false;
+  long current_offset = ftell(file);
+  if (current_offset == -1)
+    return false;
+#if defined(OS_WIN)
+  int fd = _fileno(file);
+  if (_chsize(fd, current_offset) != 0)
+    return false;
+#else
+  int fd = fileno(file);
+  if (ftruncate(fd, current_offset) != 0)
+    return false;
+#endif
+  return true;
+}
+
 bool ContainsPath(const FilePath &parent, const FilePath& child) {
   FilePath abs_parent = FilePath(parent);
   FilePath abs_child = FilePath(child);
 
   if (!file_util::AbsolutePath(&abs_parent) ||
       !file_util::AbsolutePath(&abs_child))
     return false;
 
 #if defined(OS_WIN)
   // file_util::AbsolutePath() does not flatten case on Windows, so we must do
@@ skipping 177 matching lines @@
   FilePath directory = path.DirName();
   // If there is no separator, we will get back kCurrentDirectory.
   // In this case, clear dir.
   if (directory == path || directory.value() == FilePath::kCurrentDirectory)
     dir->clear();
   else
     *dir = directory.ToWStringHack();
 }
 }  // namespace