Add an AddExtension() method in FilePath

base/file_path.cc

 // Copyright (c) 2012 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_path.h"
 
 #include <string.h>
 #include <algorithm>
 
 #include "base/basictypes.h"
@@ skipping 141 matching lines @@
       (last_separator == StringType::npos ||
       penultimate_dot > last_separator) &&
       last_dot - penultimate_dot <= 5U &&
       last_dot - penultimate_dot > 1U) {
     return penultimate_dot;
   }
 
   return last_dot;
 }
 
+// Returns true if path is "", ".", or "..".
+bool IsEmptyOrSpecialCase(const StringType& path) {
+  if (path.empty())
+    return true;
+  if (*(path.end() - 1) == FilePath::kExtensionSeparator) {

[Mark Mentovai, 2012/04/19 20:59:09]

What’s this actually buy, other than making the code obtuse? Why don’t you just
get rid of this check and proceed directly to the
kCurrentDirectory/kParentDirectory check?

[Devlin, 2012/04/21 01:37:36]

I didn't write this portion of the code (just refactored it), and noticed the
same thing.  My only guess was that it was to save that minor amount of work
since comparing the end character to see if a special case is even a concern is
faster than comparing the entirety of the path.  I'm not sure this will ever be
a concern (I'm unfamiliar with any instances of where a FilePath would be long
enough for this to matter), but I've realized a general pattern of people
preferring to not alter what is not broken.  If you like, I can simplify it.

+    // Special case "." and ".."
+    if (path == FilePath::kCurrentDirectory ||
+        path == FilePath::kParentDirectory) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
 }  // namespace
 
 FilePath::FilePath() {
 }
 
 FilePath::FilePath(const FilePath& that) : path_(that.path_) {
 }
 
 FilePath::FilePath(const StringType& path) : path_(path) {
 }
@@ skipping 199 matching lines @@
   return FilePath(path_.substr(0, dot));
 }
 
 FilePath FilePath::InsertBeforeExtension(const StringType& suffix) const {
   if (suffix.empty())
     return FilePath(path_);
 
   if (path_.empty())
     return FilePath();
 
-  StringType base = BaseName().value();
-  if (base.empty())
+  if (IsEmptyOrSpecialCase(BaseName().value()))
     return FilePath();
-  if (*(base.end() - 1) == kExtensionSeparator) {
-    // Special case "." and ".."
-    if (base == kCurrentDirectory || base == kParentDirectory) {
-      return FilePath();
-    }
-  }
 
   StringType ext = Extension();
   StringType ret = RemoveExtension().value();
   ret.append(suffix);
   ret.append(ext);
   return FilePath(ret);
 }
 
 FilePath FilePath::InsertBeforeExtensionASCII(const base::StringPiece& suffix)
     const {
   DCHECK(IsStringASCII(suffix));
 #if defined(OS_WIN)
   return InsertBeforeExtension(ASCIIToUTF16(suffix.as_string()));
 #elif defined(OS_POSIX)
   return InsertBeforeExtension(suffix.as_string());
 #endif
 }
 
+FilePath FilePath::AddExtension(const StringType& extension) const {
+  if (path_.empty())
+    return FilePath();
+
+  if (IsEmptyOrSpecialCase(BaseName().value()))
+    return FilePath();
+
+  // If the new extension is "" or ".", then just return the current FilePath.
+  if (extension.empty() || extension == StringType(1, kExtensionSeparator))
+    return *this;
+
+  StringType str = path_;
+  if (extension[0] != kExtensionSeparator &&
+      *(str.end() - 1) != kExtensionSeparator) {
+    str.append(1, kExtensionSeparator);
+  }
+  str.append(extension);
+  return FilePath(str);
+}
+
 FilePath FilePath::ReplaceExtension(const StringType& extension) const {
   if (path_.empty())
     return FilePath();
 
-  StringType base = BaseName().value();
-  if (base.empty())
+  if (IsEmptyOrSpecialCase(BaseName().value()))
     return FilePath();
-  if (*(base.end() - 1) == kExtensionSeparator) {
-    // Special case "." and ".."
-    if (base == kCurrentDirectory || base == kParentDirectory) {
-      return FilePath();
-    }
-  }
 
   FilePath no_ext = RemoveExtension();
   // If the new extension is "" or ".", then just remove the current extension.
   if (extension.empty() || extension == StringType(1, kExtensionSeparator))
     return no_ext;
 
   StringType str = no_ext.value();
   if (extension[0] != kExtensionSeparator)
     str.append(1, kExtensionSeparator);
   str.append(extension);
@@ skipping 783 matching lines @@
 #if defined(FILE_PATH_USES_WIN_SEPARATORS)
   StringType copy = path_;
   for (size_t i = 1; i < arraysize(kSeparators); ++i) {
     std::replace(copy.begin(), copy.end(), kSeparators[i], kSeparators[0]);
   }
   return FilePath(copy);
 #else
   return *this;
 #endif
 }