js/public/MemoryCallbacks.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #ifndef js_MemoryCallbacks_h
   7 #define js_MemoryCallbacks_h
   8
   9 #include "jstypes.h"
  10
  11 struct JS_PUBLIC_API JSContext;
  12
  13 namespace JS {
  14
  15 /**
  16  * If a large allocation fails when calling pod_{calloc,realloc}CanGC, the JS
  17  * engine may call the large-allocation-failure callback, if set, to allow the
  18  * embedding to flush caches, possibly perform shrinking GCs, etc. to make some
  19  * room. The allocation will then be retried (and may still fail.) This callback
  20  * can be called on any thread and must be set at most once in a process.
  21  */
  22
  23 using LargeAllocationFailureCallback = void (*)();
  24
  25 extern JS_PUBLIC_API void SetProcessLargeAllocationFailureCallback(
  26     LargeAllocationFailureCallback afc);
  27
  28 /**
  29  * Unlike the error reporter, which is only called if the exception for an OOM
  30  * bubbles up and is not caught, the OutOfMemoryCallback is called immediately
  31  * at the OOM site to allow the embedding to capture the current state of heap
  32  * allocation before anything is freed. If the large-allocation-failure callback
  33  * is called at all (not all allocation sites call the large-allocation-failure
  34  * callback on failure), it is called before the out-of-memory callback; the
  35  * out-of-memory callback is only called if the allocation still fails after the
  36  * large-allocation-failure callback has returned.
  37  */
  38
  39 using OutOfMemoryCallback = void (*)(JSContext*, void*);
  40
  41 extern JS_PUBLIC_API void SetOutOfMemoryCallback(JSContext* cx,
  42                                                  OutOfMemoryCallback cb,
  43                                                  void* data);
  44
  45 }  // namespace JS
  46
  47 #endif  // js_MemoryCallbacks_h