Implement IsAsciiUpper and IsAsciiLower in base/strings/string_util.h

base/environment.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/environment.h"
 
 #include <stddef.h>
 
 #include <vector>
 
@@ skipping 17 matching lines @@
   bool GetVar(const char* variable_name, std::string* result) override {
     if (GetVarImpl(variable_name, result))
       return true;
 
     // Some commonly used variable names are uppercase while others
     // are lowercase, which is inconsistent. Let's try to be helpful
     // and look for a variable name with the reverse case.
     // I.e. HTTP_PROXY may be http_proxy for some users/systems.
     char first_char = variable_name[0];
     std::string alternate_case_var;
-    if (first_char >= 'a' && first_char <= 'z')
+    if (IsAsciiLower(first_char))
       alternate_case_var = ToUpperASCII(variable_name);
-    else if (first_char >= 'A' && first_char <= 'Z')
+    else if (IsAsciiUpper(first_char))
       alternate_case_var = ToLowerASCII(variable_name);
     else
       return false;
     return GetVarImpl(alternate_case_var.c_str(), result);
   }
 
   bool SetVar(const char* variable_name,
               const std::string& new_value) override {
     return SetVarImpl(variable_name, new_value);
   }
@@ skipping 179 matching lines @@
   for (size_t i = 0; i < result_indices.size(); i++)
     result[i] = &storage_data[result_indices[i]];
   result[result_indices.size()] = 0;  // Null terminator.
 
   return result;
 }
 
 #endif  // OS_POSIX
 
 }  // namespace base