/src/node/deps/v8/include/v8-embedder-heap.h
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1 | | // Copyright 2021 the V8 project 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 INCLUDE_V8_EMBEDDER_HEAP_H_ |
6 | | #define INCLUDE_V8_EMBEDDER_HEAP_H_ |
7 | | |
8 | | #include "v8-traced-handle.h" // NOLINT(build/include_directory) |
9 | | #include "v8config.h" // NOLINT(build/include_directory) |
10 | | |
11 | | namespace v8 { |
12 | | namespace internal { |
13 | | class TracedHandles; |
14 | | } // namespace internal |
15 | | |
16 | | class Isolate; |
17 | | class Value; |
18 | | |
19 | | /** |
20 | | * Handler for embedder roots on non-unified heap garbage collections. |
21 | | */ |
22 | | class V8_EXPORT EmbedderRootsHandler { |
23 | | public: |
24 | | enum class RootHandling { |
25 | | kQueryEmbedderForNonDroppableReferences, |
26 | | kDontQueryEmbedderForAnyReference, |
27 | | }; |
28 | | |
29 | | virtual ~EmbedderRootsHandler() = default; |
30 | | |
31 | | EmbedderRootsHandler() = default; |
32 | | explicit EmbedderRootsHandler(RootHandling default_traced_reference_handling) |
33 | 0 | : default_traced_reference_handling_(default_traced_reference_handling) {} |
34 | | |
35 | | /** |
36 | | * Returns true if the |TracedReference| handle should be considered as root |
37 | | * for the currently running non-tracing garbage collection and false |
38 | | * otherwise. The default implementation will keep all |TracedReference| |
39 | | * references as roots. |
40 | | * |
41 | | * If this returns false, then V8 may decide that the object referred to by |
42 | | * such a handle is reclaimed. In that case, V8 calls |ResetRoot()| for the |
43 | | * |TracedReference|. |
44 | | * |
45 | | * Note that the `handle` is different from the handle that the embedder holds |
46 | | * for retaining the object. |
47 | | * |
48 | | * The concrete implementations must be thread-safe. |
49 | | */ |
50 | | virtual bool IsRoot(const v8::TracedReference<v8::Value>& handle) = 0; |
51 | | |
52 | | /** |
53 | | * Used in combination with |IsRoot|. Called by V8 when an |
54 | | * object that is backed by a handle is reclaimed by a non-tracing garbage |
55 | | * collection. It is up to the embedder to reset the original handle. |
56 | | * |
57 | | * Note that the |handle| is different from the handle that the embedder holds |
58 | | * for retaining the object. It is up to the embedder to find the original |
59 | | * handle via the object or class id. |
60 | | */ |
61 | | virtual void ResetRoot(const v8::TracedReference<v8::Value>& handle) = 0; |
62 | | |
63 | | /** |
64 | | * Similar to |ResetRoot()|, but opportunistic. The function is called in |
65 | | * parallel for different handles and as such must be thread-safe. In case, |
66 | | * |false| is returned, |ResetRoot()| will be recalled for the same handle. |
67 | | */ |
68 | 0 | virtual bool TryResetRoot(const v8::TracedReference<v8::Value>& handle) { |
69 | 0 | ResetRoot(handle); |
70 | 0 | return true; |
71 | 0 | } |
72 | | |
73 | | private: |
74 | | const RootHandling default_traced_reference_handling_ = |
75 | | RootHandling::kQueryEmbedderForNonDroppableReferences; |
76 | | |
77 | | friend class internal::TracedHandles; |
78 | | }; |
79 | | |
80 | | } // namespace v8 |
81 | | |
82 | | #endif // INCLUDE_V8_EMBEDDER_HEAP_H_ |