base/environment.h

   1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_ENVIRONMENT_H_
   6 #define BASE_ENVIRONMENT_H_
   7
   8 #include <map>
   9 #include <string>
  10
  11 #include "base/base_export.h"
  12 #include "base/memory/scoped_ptr.h"
  13 #include "base/strings/string16.h"
  14 #include "build/build_config.h"
  15
  16 namespace base {
  17
  18 namespace env_vars {
  19
  20 #if defined(OS_POSIX)
  21 BASE_EXPORT extern const char kHome[];
  22 #endif
  23
  24 }  // namespace env_vars
  25
  26 class BASE_EXPORT Environment {
  27  public:
  28   virtual ~Environment();
  29
  30   // Static factory method that returns the implementation that provide the
  31   // appropriate platform-specific instance.
  32   static Environment* Create();
  33
  34   // Gets an environment variable's value and stores it in |result|.
  35   // Returns false if the key is unset.
  36   virtual bool GetVar(const char* variable_name, std::string* result) = 0;
  37
  38   // Syntactic sugar for GetVar(variable_name, NULL);
  39   virtual bool HasVar(const char* variable_name);
  40
  41   // Returns true on success, otherwise returns false.
  42   virtual bool SetVar(const char* variable_name,
  43                       const std::string& new_value) = 0;
  44
  45   // Returns true on success, otherwise returns false.
  46   virtual bool UnSetVar(const char* variable_name) = 0;
  47 };
  48
  49
  50 #if defined(OS_WIN)
  51
  52 typedef string16 NativeEnvironmentString;
  53 typedef std::map<NativeEnvironmentString, NativeEnvironmentString>
  54     EnvironmentMap;
  55
  56 // Returns a modified environment vector constructed from the given environment
  57 // and the list of changes given in |changes|. Each key in the environment is
  58 // matched against the first element of the pairs. In the event of a match, the
  59 // value is replaced by the second of the pair, unless the second is empty, in
  60 // which case the key-value is removed.
  61 //
  62 // This Windows version takes and returns a Windows-style environment block
  63 // which is a concatenated list of null-terminated 16-bit strings. The end is
  64 // marked by a double-null terminator. The size of the returned string will
  65 // include the terminators.
  66 BASE_EXPORT string16 AlterEnvironment(const wchar_t* env,
  67                                       const EnvironmentMap& changes);
  68
  69 #elif defined(OS_POSIX)
  70
  71 typedef std::string NativeEnvironmentString;
  72 typedef std::map<NativeEnvironmentString, NativeEnvironmentString>
  73     EnvironmentMap;
  74
  75 // See general comments for the Windows version above.
  76 //
  77 // This Posix version takes and returns a Posix-style environment block, which
  78 // is a null-terminated list of pointers to null-terminated strings. The
  79 // returned array will have appended to it the storage for the array itself so
  80 // there is only one pointer to manage, but this means that you can't copy the
  81 // array without keeping the original around.
  82 BASE_EXPORT scoped_ptr<char*[]> AlterEnvironment(
  83     const char* const* env,
  84     const EnvironmentMap& changes);
  85
  86 #endif
  87
  88 }  // namespace base
  89
  90 #endif  // BASE_ENVIRONMENT_H_