1 // Copyright (c) 2010 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 SANDBOX_SRC_SHARED_HANDLES_H__ 6 #define SANDBOX_SRC_SHARED_HANDLES_H__ 7 8 #include "base/basictypes.h" 9 10 #ifndef HANDLE 11 // We can provide our own windows compatilble handle definition, but 12 // in general we want to rely on the client of this api to include 13 // the proper windows headers. Note that we don't want to bring the 14 // whole <windows.h> into scope if we don't have to. 15 typedef void* HANDLE; 16 #endif 17 18 namespace sandbox { 19 20 // SharedHandles is a simple class to stash and find windows object handles 21 // given a raw block of memory which is shared between two processes. 22 // It addresses the need to communicate a handle value between two windows 23 // processes given that they are already sharing some memory. 24 // 25 // This class is not exposed directly to users of the sanbox API, instead 26 // we expose the wrapper methods TargetProcess::TransferHandle( ) and 27 // TargetServices::GetTransferHandle() 28 // 29 // Use it for a small number of items, since internaly uses linear seach 30 // 31 // The use is very simple. Given a shared memory between proces A and B: 32 // process A: 33 // HANDLE handle = SomeFunction(..); 34 // SharedHandles shared_handes; 35 // shared_handles.Init(memory) 36 // shared_handles.SetHandle(3, handle); 37 // 38 // process B: 39 // SharedHandles shared_handes; 40 // shared_handles.Init(memory) 41 // HANDLE handle = shared_handles.GetHandle(3); 42 // 43 // Note that '3' in this example is a unique id, that must be agreed before 44 // transfer 45 // 46 // Note2: While this class can be used in a single process, there are 47 // better alternatives such as STL 48 // 49 // Note3: Under windows a kernel object handle in one process does not 50 // make sense for another process unless there is a DuplicateHandle( ) 51 // call involved which this class DOES NOT do that for you. 52 // 53 // Note4: Under windows, shared memory when created is initialized to 54 // zeros always. If you are not using shared memory it is your responsability 55 // to zero it for the setter process and to copy it to the getter process. 56 class SharedHandles { 57 public: 58 SharedHandles(); 59 60 // Initializes the shared memory for use. 61 // Pass the shared memory base and size. It will internally compute 62 // how many handles can it store. If initialization fails the return value 63 // is false. 64 bool Init(void* raw_mem, size_t size_bytes); 65 66 // Sets a handle in the shared memory for transfer. 67 // Parameters: 68 // tag : an integer, different from zero that uniquely identfies the 69 // handle to transfer. 70 // handle: the handle value associated with 'tag' to tranfer 71 // Returns false if there is not enough space in the shared memory for 72 // this handle. 73 bool SetHandle(uint32 tag, HANDLE handle); 74 75 // Gets a handle previously stored by SetHandle. 76 // Parameters: 77 // tag: an integer different from zero that uniquely identfies the handle 78 // to retrieve. 79 // *handle: output handle value if the call was succesful. 80 // If a handle with the provided tag is not found the return value is false. 81 // If the tag is found the return value is true. 82 bool GetHandle(uint32 tag, HANDLE* handle); 83 84 private: 85 // A single item is the tuple handle/tag 86 struct SharedItem { 87 uint32 tag; 88 void* item; 89 }; 90 91 // SharedMem is used to layout the memory as an array of SharedItems 92 struct SharedMem { 93 size_t max_items; 94 SharedItem* items; 95 }; 96 97 // Finds an Item tuple provided the handle tag. 98 // Uses linear search because we expect the number of handles to be 99 // small (say less than ~100). 100 SharedItem* FindByTag(uint32 tag); 101 102 SharedMem shared_; 103 DISALLOW_COPY_AND_ASSIGN(SharedHandles); 104 }; 105 106 } // namespace sandbox 107 108 #endif // SANDBOX_SRC_SHARED_HANDLES_H__ 109
