Add read-only mode to CommandLine that optimizes HasSwitch(const char*).

base/command_line.h

 // 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.
 
 // This class works with command lines: building and parsing.
 // Arguments with prefixes ('--', '-', and on Windows, '/') are switches.
 // Switches will precede all other arguments without switch prefixes.
 // Switches can optionally have values, delimited by '=', e.g., "-switch=value".
 // An argument of "--" will terminate switch parsing during initialization,
 // interpreting subsequent tokens as non-switch arguments, regardless of prefix.
@@ skipping 138 matching lines @@
   bool HasSwitch(const char switch_constant[]) const;
 
   // Returns the value associated with the given switch. If the switch has no
   // value or isn't present, this method returns the empty string.
   std::string GetSwitchValueASCII(const std::string& switch_string) const;
   FilePath GetSwitchValuePath(const std::string& switch_string) const;
   StringType GetSwitchValueNative(const std::string& switch_string) const;
 
   // Get a copy of all switches, along with their values.
   const SwitchMap& GetSwitches() const { return switches_; }
+  const std::vector<std::string>& GetSwitchVector() const {
+    return switch_vector_;
+  }
 
   // Append a switch [with optional value] to the command line.
   // Note: Switches will precede arguments regardless of appending order.
   void AppendSwitch(const std::string& switch_string);
   void AppendSwitchPath(const std::string& switch_string,
                         const FilePath& path);
   void AppendSwitchNative(const std::string& switch_string,
                           const StringType& value);
   void AppendSwitchASCII(const std::string& switch_string,
                          const std::string& value);
@@ skipping 22 matching lines @@
   // Insert a command before the current command.
   // Common for debuggers, like "valgrind" or "gdb --args".
   void PrependWrapper(const StringType& wrapper);
 
 #if defined(OS_WIN)
   // Initialize by parsing the given command line string.
   // The program name is assumed to be the first item in the string.
   void ParseFromString(const base::string16& command_line);
 #endif
 
+  // Optimizes lookups into this CommandLine, but it can no longer be modified.
+  void MakeReadOnly();
+
  private:
   // Disallow default constructor; a program name must be explicitly specified.
   CommandLine();
   // Allow the copy constructor. A common pattern is to copy of the current
   // process's command line and then add some flags to it. For example:
   //   CommandLine cl(*CommandLine::ForCurrentProcess());
   //   cl.AppendSwitch(...);
 
   // Internal version of GetCommandLineString. If |quote_placeholders| is true,
   // also quotes parts with '%' in them.
   StringType GetCommandLineStringInternal(bool quote_placeholders) const;
 
   // Internal version of GetArgumentsString. If |quote_placeholders| is true,
   // also quotes parts with '%' in them.
   StringType GetArgumentsStringInternal(bool quote_placeholders) const;
 
+  // Search for the switch in |switch_vector_|.
+  bool HasSwitchVector(const char string_constant[]) const;
+
+  // Search for the switch assuming the input is lowercase.
+  bool HasSwitchLowerCase(const char string_constant[]) const;
+
   // The singleton CommandLine representing the current process's command line.
   static CommandLine* current_process_commandline_;
 
   // The argv array: { program, [(--|-|/)switch[=value]]*, [--], [argument]* }
   StringVector argv_;
 
   // Parsed-out switch keys and values.
   SwitchMap switches_;
 
   // The index after the program and switches, any arguments start here.
   size_t begin_args_;
+
+  // A vector of switches. This allows looking up a const char* switch without
+  // allocating a string. It is initialized when this CommandLine is made
+  // read-only.
+  std::vector<std::string> switch_vector_;
+
+  // This is un-set when this CommandLine is made read-only.
+  bool writeable_;
 };
 
 }  // namespace base
 
 #endif  // BASE_COMMAND_LINE_H_