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

base/command_line.cc

Index: base/command_line.cc
diff --git a/base/command_line.cc b/base/command_line.cc
index 3e143cc5d449f358936726f33c8d3fda95064f03..7dab0db479b6447119a9d1ea64c6a2e6c4174c67 100644
--- a/base/command_line.cc
+++ b/base/command_line.cc
@@ -5,6 +5,7 @@
 #include "base/command_line.h"
 
 #include <algorithm>
+#include <cstring>
 #include <ostream>
 
 #include "base/basictypes.h"
@@ -93,6 +94,14 @@ void AppendSwitchesAndArguments(CommandLine* command_line,
   }
 }
 
+bool ContainsUpperASCII(const char* string) {
+  for (; *string; ++string) {
+    if (*string >= 'A' && *string <= 'Z')
+      return true;
+  }
+  return false;
+}
+
 // Lowercase switches for backwards compatiblity *on Windows*.
 #if defined(OS_WIN)
 std::string LowerASCIIOnWindows(const std::string& string) {
@@ -104,6 +113,10 @@ const std::string& LowerASCIIOnWindows(const std::string& string) {
 }
 #endif
 
+// Comparator usable by std::lower_bound().
+bool CompareStringAndCharPtr(const std::string& s, const char* c) {
+  return strcmp(s.c_str(), c) <= 0;
+}
 
 #if defined(OS_WIN)
 // Quote a string as necessary for CommandLineToArgvW compatiblity *on Windows*.
@@ -158,25 +171,21 @@ string16 QuoteForCommandLineToArgvW(const string16& arg,
 }  // namespace
 
 CommandLine::CommandLine(NoProgram no_program)
-    : argv_(1),
-      begin_args_(1) {
+    : argv_(1), begin_args_(1), writeable_(true) {
 }
 
 CommandLine::CommandLine(const FilePath& program)
-    : argv_(1),
-      begin_args_(1) {
+    : argv_(1), begin_args_(1), writeable_(true) {
   SetProgram(program);
 }
 
 CommandLine::CommandLine(int argc, const CommandLine::CharType* const* argv)
-    : argv_(1),
-      begin_args_(1) {
+    : argv_(1), begin_args_(1), writeable_(true) {
   InitFromArgv(argc, argv);
 }
 
 CommandLine::CommandLine(const StringVector& argv)
-    : argv_(1),
-      begin_args_(1) {
+    : argv_(1), begin_args_(1), writeable_(true) {
   InitFromArgv(argv);
 }
 
@@ -207,6 +216,7 @@ bool CommandLine::Init(int argc, const char* const* argv) {
 #elif defined(OS_POSIX)
   current_process_commandline_->InitFromArgv(argc, argv);
 #endif
+  current_process_commandline_->MakeReadOnly();
 
   return true;
 }
@@ -240,6 +250,7 @@ CommandLine CommandLine::FromString(const string16& command_line) {
 
 void CommandLine::InitFromArgv(int argc,
                                const CommandLine::CharType* const* argv) {
+  DCHECK(writeable_);
   StringVector new_argv;
   for (int i = 0; i < argc; ++i)
     new_argv.push_back(argv[i]);
@@ -247,6 +258,7 @@ void CommandLine::InitFromArgv(int argc,
 }
 
 void CommandLine::InitFromArgv(const StringVector& argv) {
+  DCHECK(writeable_);
   argv_ = StringVector(1);
   switches_.clear();
   begin_args_ = 1;
@@ -259,15 +271,24 @@ FilePath CommandLine::GetProgram() const {
 }
 
 void CommandLine::SetProgram(const FilePath& program) {
+  DCHECK(writeable_);
   TrimWhitespace(program.value(), TRIM_ALL, &argv_[0]);
 }
 
 bool CommandLine::HasSwitch(const std::string& switch_string) const {
-  return switches_.find(LowerASCIIOnWindows(switch_string)) != switches_.end();
+#if defined(OS_WIN)
+  if (ContainsUpperASCII(switch_string.c_str()))
+    return switches_.find(LowerASCIIOnWindows(switch_string)) !=
+           switches_.end();
+#endif
+
+  return switches_.find(switch_string) != switches_.end();
 }
 
 bool CommandLine::HasSwitch(const char string_constant[]) const {
-  return HasSwitch(std::string(string_constant));
+  DCHECK(!ContainsUpperASCII(string_constant));
+  return writeable_ ? HasSwitchLowerCase(string_constant)
+                    : HasSwitchVector(string_constant);
 }
 
 std::string CommandLine::GetSwitchValueASCII(
@@ -291,8 +312,15 @@ FilePath CommandLine::GetSwitchValuePath(
 
 CommandLine::StringType CommandLine::GetSwitchValueNative(
     const std::string& switch_string) const {
-  SwitchMap::const_iterator result =
-    switches_.find(LowerASCIIOnWindows(switch_string));
+#if defined(OS_WIN)
+  if (ContainsUpperASCII(switch_string.c_str())) {
+    SwitchMap::const_iterator result =
+        switches_.find(LowerASCIIOnWindows(switch_string));
+    return result == switches_.end() ? StringType() : result->second;
+  }
+#endif
+
+  SwitchMap::const_iterator result = switches_.find(switch_string);
   return result == switches_.end() ? StringType() : result->second;
 }
 
@@ -307,6 +335,7 @@ void CommandLine::AppendSwitchPath(const std::string& switch_string,
 
 void CommandLine::AppendSwitchNative(const std::string& switch_string,
                                      const CommandLine::StringType& value) {
+  DCHECK(writeable_);
   std::string switch_key(LowerASCIIOnWindows(switch_string));
 #if defined(OS_WIN)
   StringType combined_switch_string(ASCIIToUTF16(switch_key));
@@ -326,6 +355,7 @@ void CommandLine::AppendSwitchNative(const std::string& switch_string,
 
 void CommandLine::AppendSwitchASCII(const std::string& switch_string,
                                     const std::string& value_string) {
+  DCHECK(writeable_);
 #if defined(OS_WIN)
   AppendSwitchNative(switch_string, ASCIIToUTF16(value_string));
 #elif defined(OS_POSIX)
@@ -336,6 +366,7 @@ void CommandLine::AppendSwitchASCII(const std::string& switch_string,
 void CommandLine::CopySwitchesFrom(const CommandLine& source,
                                    const char* const switches[],
                                    size_t count) {
+  DCHECK(writeable_);
   for (size_t i = 0; i < count; ++i) {
     if (source.HasSwitch(switches[i]))
       AppendSwitchNative(switches[i], source.GetSwitchValueNative(switches[i]));
@@ -367,17 +398,20 @@ void CommandLine::AppendArgPath(const FilePath& path) {
 }
 
 void CommandLine::AppendArgNative(const CommandLine::StringType& value) {
+  DCHECK(writeable_);
   argv_.push_back(value);
 }
 
 void CommandLine::AppendArguments(const CommandLine& other,
                                   bool include_program) {
+  DCHECK(writeable_);
   if (include_program)
     SetProgram(other.GetProgram());
   AppendSwitchesAndArguments(this, other.argv());
 }
 
 void CommandLine::PrependWrapper(const CommandLine::StringType& wrapper) {
+  DCHECK(writeable_);
   if (wrapper.empty())
     return;
   // The wrapper may have embedded arguments (like "gdb --args"). In this case,
@@ -391,6 +425,7 @@ void CommandLine::PrependWrapper(const CommandLine::StringType& wrapper) {
 
 #if defined(OS_WIN)
 void CommandLine::ParseFromString(const string16& command_line) {
+  DCHECK(writeable_);
   string16 command_line_string;
   TrimWhitespace(command_line, TRIM_ALL, &command_line_string);
   if (command_line_string.empty())
@@ -407,6 +442,12 @@ void CommandLine::ParseFromString(const string16& command_line) {
 }
 #endif
 
+void CommandLine::MakeReadOnly() {
+  for (const auto& i : switches_)
+    switch_vector_.push_back(i.first);
+  std::sort(switch_vector_.begin(), switch_vector_.end());
+}
+
 CommandLine::StringType CommandLine::GetCommandLineStringInternal(
     bool quote_placeholders) const {
   StringType string(argv_[0]);
@@ -452,4 +493,15 @@ CommandLine::StringType CommandLine::GetArgumentsStringInternal(
   return params;
 }
 
+bool CommandLine::HasSwitchVector(const char string_constant[]) const {
+  DCHECK(!writeable_);
+  auto lb = std::lower_bound(switch_vector_.begin(), switch_vector_.end(),
+                             string_constant, CompareStringAndCharPtr);
+  return lb != switch_vector_.end() && !strcmp(lb->c_str(), string_constant);
+}
+
+bool CommandLine::HasSwitchLowerCase(const char string_constant[]) const {
+  return switches_.find(std::string(string_constant)) != switches_.end();
+}
+
 }  // namespace base