Index: base/memory/shared_memory_allocator.h |
diff --git a/base/memory/shared_memory_allocator.h b/base/memory/shared_memory_allocator.h |
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+// Copyright (c) 2015 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_MEMORY_SHARED_MEMORY_ALLOCATOR_H_ |
+#define BASE_MEMORY_SHARED_MEMORY_ALLOCATOR_H_ |
+ |
+#include "base/base_export.h" |
+#include "base/basictypes.h" |
+ |
+namespace base { |
+ |
+// Simple allocator for pieces of a memory block that may be shared across |
+// multiple processes. |
chrisha
2015/10/29 21:05:14
More detailed comments about the thread safety gua
bcwhite
2015/10/29 23:40:58
Done.
|
+class BASE_EXPORT SharedMemoryAllocator { |
+ public: |
+ struct Iterator { |
+ int32 last; |
+ }; |
+ |
+ struct MemoryInfo { |
+ int32 total; |
+ int32 free; |
+ }; |
+ |
+ // The allocator operates on any arbitrary block of memory. Creation and |
+ // sharing of that block with another process is the responsibility of the |
+ // caller. The allocator needs to know only the block's |base| address, the |
chrisha
2015/10/29 21:05:14
micronit: The more common pattern in Chrome is a s
bcwhite
2015/10/29 23:40:58
I can't. I'm sorry. <hanging head in shame> Bla
chrisha
2015/10/30 14:36:46
http://www.slate.com/articles/technology/technolog
bcwhite
2015/10/30 15:15:35
Heh! Yeah, I've read that. It even makes sense.
|
+ // total |size| of the block, and any internal |page| size (zero if not |
+ // paged) across which allocations should not span. |
+ // |
+ // SharedMemoryAllocator does NOT take ownership of this memory block. The |
+ // caller must manage it and ensure it stays available throughout the lifetime |
+ // of this object. |
+ SharedMemoryAllocator(void* base, int32 size, int32 page); |
chrisha
2015/10/29 21:05:14
(We now use int32_t instead of int32.)
Shouldn't
bcwhite
2015/10/29 23:40:57
Awww.... shoot.
chrisha
2015/10/30 14:36:46
Okay, sounds like a reasonable reason to me. Worth
bcwhite
2015/10/30 15:15:35
Done.
|
+ ~SharedMemoryAllocator(); |
+ |
+ // Get an object referenced by an |offset|. For safety reasons, the |type| |
+ // code and size-of |unused| are compared to ensure the reference is valid |
+ // and cannot return an object outside of the memory segment. A |type| of |
+ // zero will match any though the size is still checked. NULL is returned |
+ // if any problem is detected, such as corrupted storage or incorrect |
+ // parameters. Callers MUST check that the returned value is not-null EVERY |
+ // TIME before accessing it or risk crashing! Once dereferenced, the pointer |
+ // is safe to reuse forever. |
+ template<typename T> T* GetObject(int32 offset, int32 type, T* unused) { |
chrisha
2015/10/29 21:05:14
Why pass a T* unused instead of just getting havin
bcwhite
2015/10/29 23:40:58
That works. Done.
chrisha
2015/10/30 14:36:46
The offset isn't sufficient in this case, because
bcwhite
2015/10/30 15:15:35
Acknowledged.
|
+ return static_cast<T*>(GetBlockData(offset, type, sizeof(T), false)); |
+ } |
+ |
+ // Reserve space in the memory segment of the desired |size| and |type|. |
+ // A return value of zero indicates the allocation failed, otherwise the |
+ // returned offset can be used by any process to get a real pointer via |
+ // the GetObject() call. |
+ int32 Allocate(int32 size, int32 type); |
+ |
+ // Get the information about the amount of free space in the allocator. The |
+ // amount of free space should be treated as approximate due to extras from |
+ // alignment and meta-data, but will never return less than could actually |
+ // be allocated. |
+ void GetMemoryInfo(MemoryInfo* meminfo); |
+ |
+ // Allocated objects can be added to an internal list that can then be |
+ // iterated over by other processes. |
+ void MakeIterable(int32 offset); |
chrisha
2015/10/29 21:05:14
Why do you need this? The implementation already h
bcwhite
2015/10/29 23:40:58
Unfortunately, it doesn't. If you try to make it
chrisha
2015/10/30 14:36:46
Still implementation details. This should be entir
bcwhite
2015/10/30 15:15:35
Acknowledged.
|
+ |
+ // Iterating uses a |state| structure (initialized by GetFirstIterable) and |
+ // returns both the offset reference to the object as well as the |type| of |
+ // that object. A zero return value indicates there are currently no more |
+ // objects to be found but future attempts can be made without having to |
+ // reset the iterator to "first". |
+ int32 GetFirstIterable(Iterator* state, int32* type); |
+ int32 GetNextIterable(Iterator* state, int32* type); |
+ |
+ // If there is some indication that the shared memory has become corrupted, |
+ // calling this will attempt to prevent further damage by indicating to |
+ // all processes that something is not as expected. |
+ void SetCorrupted(); |
+ bool IsCorrupted(); |
+ |
+ // Flag set if an allocation has failed because memory was full. |
+ bool IsFull(); |
+ |
+ private: |
+ struct SharedMetaData; |
chrisha
2015/10/29 21:05:14
Metadata is a single word, no need to capitalize D
bcwhite
2015/10/29 23:40:58
Done.
|
+ struct BlockHeader; |
+ |
+ BlockHeader* GetBlock(int32 offset, int32 type, int32 size, bool special); |
+ void* GetBlockData(int32 offset, int32 type, int32 size, bool special); |
+ |
+ SharedMetaData* shared_meta_; |
+ char* mem_base_; // char because sizeof guaranteed 1 -- easy offset calc |
+ int32 mem_size_; |
+ int32 mem_page_; |
chrisha
2015/10/29 21:05:14
Do we really care about page sizes? What's the har
bcwhite
2015/10/29 23:40:58
Probably not. However, if this were to be used ag
chrisha
2015/10/30 14:36:46
Okay, I'm fine with that.
|
+ int32 last_seen_; |
+ bool corrupted_; |
+ |
+ DISALLOW_COPY_AND_ASSIGN(SharedMemoryAllocator); |
+}; |
+} // namespace base |
+ |
+#endif // BASE_MEMORY_SHARED_MEMORY_ALLOCATOR_H_ |