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
16namespace base {
17
18namespace env_vars {
19
20#if defined(OS_POSIX)
21BASE_EXPORT extern const char kHome[];
22#endif
23
24}  // namespace env_vars
25
26class 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
52typedef string16 NativeEnvironmentString;
53typedef 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.
66BASE_EXPORT string16 AlterEnvironment(const wchar_t* env,
67                                      const EnvironmentMap& changes);
68
69#elif defined(OS_POSIX)
70
71typedef std::string NativeEnvironmentString;
72typedef 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.
82BASE_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_
91