js/public/MemoryFunctions.h
author Jon Coppeard <jcoppeard@mozilla.com>
Wed, 22 May 2019 17:45:03 +0100
changeset 475397 740009023b1b6867a18b8f2f44e0ba84bfa229ec
parent 472078 24e75c822fd37393db9b1237ca42defe4ac89639
child 478500 0943e5feaa8dba351ac8fdd1a9f3b6a66e98c78b
permissions -rw-r--r--
Bug 1395509 - Pack MemoryTracker hashtable keys into a single word on 64bit platforms r=sfink This code is debug-only, but it seems a shame to waste have this key structure take up two words when it will fix into one. This also moves the MemoryUse enum definition to gc/GCEnum.h. Differential Revision: https://phabricator.services.mozilla.com/D32170

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/* Low-level memory-allocation functions. */

#ifndef js_MemoryFunctions_h
#define js_MemoryFunctions_h

#include "mozilla/Assertions.h"  // MOZ_ASSERT
#include "mozilla/Attributes.h"  // MOZ_MUST_USE

#include <stddef.h>  // size_t

#include "jstypes.h"  // JS_PUBLIC_API

struct JSContext;
class JSObject;
struct JSRuntime;

struct JSFreeOp {
 protected:
  JSRuntime* runtime_;

  explicit JSFreeOp(JSRuntime* rt) : runtime_(rt) {}

 public:
  JSRuntime* runtime() const {
    MOZ_ASSERT(runtime_);
    return runtime_;
  }
};

extern JS_PUBLIC_API void* JS_malloc(JSContext* cx, size_t nbytes);

extern JS_PUBLIC_API void* JS_realloc(JSContext* cx, void* p, size_t oldBytes,
                                      size_t newBytes);

/**
 * A wrapper for |js_free(p)| that may delay |js_free(p)| invocation as a
 * performance optimization.  |cx| may be nullptr.
 */
extern JS_PUBLIC_API void JS_free(JSContext* cx, void* p);

/**
 * Same as above, but for buffers that will be used with the BYOB
 * (Bring Your Own Buffer) JSString creation functions, such as
 * JS_NewLatin1String and JS_NewUCString
 */
extern JS_PUBLIC_API void* JS_string_malloc(JSContext* cx, size_t nbytes);

extern JS_PUBLIC_API void* JS_string_realloc(JSContext* cx, void* p,
                                             size_t oldBytes, size_t newBytes);

extern JS_PUBLIC_API void JS_string_free(JSContext* cx, void* p);

/**
 * A wrapper for |js_free(p)| that may delay |js_free(p)| invocation as a
 * performance optimization as specified by the given JSFreeOp instance.
 */
extern JS_PUBLIC_API void JS_freeop(JSFreeOp* fop, void* p);

namespace JS {

/**
 * The different possible memory uses to pass to Add/RemoveAssociatedMemory.
 */
#define JS_FOR_EACH_PUBLIC_MEMORY_USE(_) \
  _(XPCWrappedNative)                    \
  _(DOMBinding)

enum class MemoryUse : uint8_t {
#define DEFINE_MEMORY_USE(Name) Name,
  JS_FOR_EACH_PUBLIC_MEMORY_USE(DEFINE_MEMORY_USE)
#undef DEFINE_MEMORY_USE
};

/**
 * Advise the GC of external memory owned by a JSObject. This is used to
 * determine when to collect zones. Calls must be matched by calls to
 * RemoveAssociatedMemory() when the memory is deallocated or no longer owned by
 * the object.
 */
extern JS_PUBLIC_API void AddAssociatedMemory(JSObject* obj, size_t nbytes,
                                              MemoryUse use);

/**
 * Advise the GC that external memory reported by JS::AddAssociatedMemory() is
 * no longer owned by a JSObject. Calls must match those to
 * AddAssociatedMemory().
 */
extern JS_PUBLIC_API void RemoveAssociatedMemory(JSObject* obj, size_t nbytes,
                                                 MemoryUse use);

}  // namespace JS

#endif /* js_MemoryFunctions_h */