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_EMBEDDER_PLATFORM_SHARED_BUFFER_H_ 6 #define MOJO_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/embedder/scoped_platform_handle.h" 14 #include "mojo/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 PlatformSharedBuffer()69 PlatformSharedBuffer() {} ~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. ~PlatformSharedBufferMapping()87 virtual ~PlatformSharedBufferMapping() {} 88 89 virtual void* GetBase() const = 0; 90 virtual size_t GetLength() const = 0; 91 92 protected: PlatformSharedBufferMapping()93 PlatformSharedBufferMapping() {} 94 95 private: 96 DISALLOW_COPY_AND_ASSIGN(PlatformSharedBufferMapping); 97 }; 98 99 } // namespace embedder 100 } // namespace mojo 101 102 #endif // MOJO_EMBEDDER_PLATFORM_SHARED_BUFFER_H_ 103