| // Copyright (c) 2009 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. |
| |
| #ifndef BASE_GLOBAL_DESCRIPTORS_POSIX_H_ |
| #define BASE_GLOBAL_DESCRIPTORS_POSIX_H_ |
| #pragma once |
| |
| #include "build/build_config.h" |
| |
| #include <vector> |
| #include <utility> |
| |
| #include <stdint.h> |
| |
| #include "base/singleton.h" |
| |
| namespace base { |
| |
| // It's common practice to install file descriptors into well known slot |
| // numbers before execing a child; stdin, stdout and stderr are ubiqutous |
| // examples. |
| // |
| // However, when using a zygote model, this becomes troublesome. Since the |
| // descriptors which need to be in these slots generally aren't known, any code |
| // could open a resource and take one of the reserved descriptors. Simply |
| // overwriting the slot isn't a viable solution. |
| // |
| // We could try to fill the reserved slots as soon as possible, but this is a |
| // fragile solution since global constructors etc are able to open files. |
| // |
| // Instead, we retreat from the idea of installing descriptors in specific |
| // slots and add a layer of indirection in the form of this singleton object. |
| // It maps from an abstract key to a descriptor. If independent modules each |
| // need to define keys, then values should be chosen randomly so as not to |
| // collide. |
| class GlobalDescriptors { |
| public: |
| typedef uint32_t Key; |
| // Often we want a canonical descriptor for a given Key. In this case, we add |
| // the following constant to the key value: |
| static const int kBaseDescriptor = 3; // 0, 1, 2 are already taken. |
| |
| // Get a descriptor given a key. It is a fatal error if the key is not known. |
| int Get(Key key) const; |
| // Get a descriptor give a key. Returns -1 on error. |
| int MaybeGet(Key key) const; |
| |
| typedef std::vector<std::pair<Key, int> > Mapping; |
| |
| // Set the descriptor for the given key. |
| void Set(Key key, int fd); |
| |
| void Reset(const Mapping& mapping) { |
| descriptors_ = mapping; |
| } |
| |
| private: |
| GlobalDescriptors(); |
| ~GlobalDescriptors(); |
| friend struct DefaultSingletonTraits<GlobalDescriptors>; |
| |
| Mapping descriptors_; |
| }; |
| |
| } // namespace base |
| |
| #endif // BASE_GLOBAL_DESCRIPTORS_POSIX_H_ |