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1 // Copyright 2014 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 MOJO_EDK_EMBEDDER_PLATFORM_SHARED_BUFFER_H_ | |
6 #define MOJO_EDK_EMBEDDER_PLATFORM_SHARED_BUFFER_H_ | |
7 | |
8 #include <stddef.h> | |
9 | |
10 #include "base/macros.h" | |
11 #include "base/memory/ref_counted.h" | |
12 #include "base/memory/scoped_ptr.h" | |
13 #include "mojo/edk/embedder/scoped_platform_handle.h" | |
14 #include "mojo/edk/system/system_impl_export.h" | |
15 | |
16 namespace mojo { | |
17 namespace embedder { | |
18 | |
19 class PlatformSharedBufferMapping; | |
20 | |
21 // |PlatformSharedBuffer| is an interface for a thread-safe, ref-counted wrapper | |
22 // around OS-specific shared memory. It has the following features: | |
23 // - A |PlatformSharedBuffer| simply represents a piece of shared memory that | |
24 // *may* be mapped and *may* be shared to another process. | |
25 // - A single |PlatformSharedBuffer| may be mapped multiple times. The | |
26 // lifetime of the mapping (owned by |PlatformSharedBufferMapping|) is | |
27 // separate from the lifetime of the |PlatformSharedBuffer|. | |
28 // - Sizes/offsets (of the shared memory and mappings) are arbitrary, and not | |
29 // restricted by page size. However, more memory may actually be mapped than | |
30 // requested. | |
31 // | |
32 // It currently does NOT support the following: | |
33 // - Sharing read-only. (This will probably eventually be supported.) | |
34 // | |
35 // TODO(vtl): Rectify this with |base::SharedMemory|. | |
36 class MOJO_SYSTEM_IMPL_EXPORT PlatformSharedBuffer | |
37 : public base::RefCountedThreadSafe<PlatformSharedBuffer> { | |
38 public: | |
39 // Gets the size of shared buffer (in number of bytes). | |
40 virtual size_t GetNumBytes() const = 0; | |
41 | |
42 // Maps (some) of the shared buffer into memory; [|offset|, |offset + length|] | |
43 // must be contained in [0, |num_bytes|], and |length| must be at least 1. | |
44 // Returns null on failure. | |
45 virtual scoped_ptr<PlatformSharedBufferMapping> Map(size_t offset, | |
46 size_t length) = 0; | |
47 | |
48 // Checks if |offset| and |length| are valid arguments. | |
49 virtual bool IsValidMap(size_t offset, size_t length) = 0; | |
50 | |
51 // Like |Map()|, but doesn't check its arguments (which should have been | |
52 // preflighted using |IsValidMap()|). | |
53 virtual scoped_ptr<PlatformSharedBufferMapping> MapNoCheck(size_t offset, | |
54 size_t length) = 0; | |
55 | |
56 // Duplicates the underlying platform handle and passes it to the caller. | |
57 // TODO(vtl): On POSIX, we'll need two FDs to support sharing read-only. | |
58 virtual ScopedPlatformHandle DuplicatePlatformHandle() = 0; | |
59 | |
60 // Passes the underlying platform handle to the caller. This should only be | |
61 // called if there's a unique reference to this object (owned by the caller). | |
62 // After calling this, this object should no longer be used, but should only | |
63 // be disposed of. | |
64 virtual ScopedPlatformHandle PassPlatformHandle() = 0; | |
65 | |
66 protected: | |
67 friend class base::RefCountedThreadSafe<PlatformSharedBuffer>; | |
68 | |
69 PlatformSharedBuffer() {} | |
70 virtual ~PlatformSharedBuffer() {} | |
71 | |
72 private: | |
73 DISALLOW_COPY_AND_ASSIGN(PlatformSharedBuffer); | |
74 }; | |
75 | |
76 // An interface for a mapping of a |PlatformSharedBuffer| (compararable to a | |
77 // "file view" in Windows); see above. Created by (implementations of) | |
78 // |PlatformSharedBuffer::Map()|. Automatically unmaps memory on destruction. | |
79 // | |
80 // Mappings are NOT thread-safe. | |
81 // | |
82 // Note: This is an entirely separate class (instead of | |
83 // |PlatformSharedBuffer::Mapping|) so that it can be forward-declared. | |
84 class MOJO_SYSTEM_IMPL_EXPORT PlatformSharedBufferMapping { | |
85 public: | |
86 // IMPORTANT: Implementations must implement a destructor that unmaps memory. | |
87 virtual ~PlatformSharedBufferMapping() {} | |
88 | |
89 virtual void* GetBase() const = 0; | |
90 virtual size_t GetLength() const = 0; | |
91 | |
92 protected: | |
93 PlatformSharedBufferMapping() {} | |
94 | |
95 private: | |
96 DISALLOW_COPY_AND_ASSIGN(PlatformSharedBufferMapping); | |
97 }; | |
98 | |
99 } // namespace embedder | |
100 } // namespace mojo | |
101 | |
102 #endif // MOJO_EDK_EMBEDDER_PLATFORM_SHARED_BUFFER_H_ | |
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