Quelle  ArrayBufferObjectMaybeShared.cpp

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

#include <stdint.h>  // uint8_t, uint32_t

#include "jstypes.h"  // JS_PUBLIC_API

#include "js/ArrayBufferMaybeShared.h"
#include "vm/ArrayBufferObject.h"  // js::ArrayBufferObject
#include "vm/JSObject.h"           // JSObject
#include "vm/SharedArrayObject.h"  // js::SharedArrayBufferObject
#include "vm/SharedMem.h"          // SharedMem

using namespace js;

JS_PUBLIC_API bool JS::IsArrayBufferObjectMaybeShared(JSObject* obj) {
  return obj->canUnwrapAs<ArrayBufferObjectMaybeShared>();
}

JS_PUBLIC_API JSObject* JS::UnwrapArrayBufferMaybeShared(JSObject* obj) {
  return obj->maybeUnwrapIf<ArrayBufferObjectMaybeShared>();
}

JS_PUBLIC_API void JS::GetArrayBufferMaybeSharedLengthAndData(
    JSObject* obj, size_t* length, bool* isSharedMemory, uint8_t** data) {
  MOZ_ASSERT(obj->is<ArrayBufferObjectMaybeShared>());

  if (obj->is<SharedArrayBufferObject>()) {
    auto* buffer = &obj->as<SharedArrayBufferObject>();
    *length = buffer->byteLength();
    *data = buffer->dataPointerShared().unwrap();
    *isSharedMemory = true;
  } else {
    auto* buffer = &obj->as<ArrayBufferObject>();
    *length = buffer->byteLength();
    *data = buffer->dataPointer();
    *isSharedMemory = false;
  }
}

JS_PUBLIC_API uint8_t* JS::GetArrayBufferMaybeSharedData(
    JSObject* obj, bool* isSharedMemory, const JS::AutoRequireNoGC&) {
  MOZ_ASSERT(obj->maybeUnwrapIf<ArrayBufferObjectMaybeShared>());

  if (ArrayBufferObject* aobj = obj->maybeUnwrapIf<ArrayBufferObject>()) {
    *isSharedMemory = false;
    return aobj->dataPointer();
  } else if (SharedArrayBufferObject* saobj =
                 obj->maybeUnwrapIf<SharedArrayBufferObject>()) {
    *isSharedMemory = true;
    return saobj->dataPointerShared().unwrap();
  }

  return nullptr;
}

JS_PUBLIC_API bool JS::IsLargeArrayBufferMaybeShared(JSObject* obj) {
#ifdef JS_64BIT
  obj = UnwrapArrayBufferMaybeShared(obj);
  MOZ_ASSERT(obj);
  size_t len = obj->is<ArrayBufferObject>()
                   ? obj->as<ArrayBufferObject>().byteLength()
                   : obj->as<SharedArrayBufferObject>().byteLength();
  return len > ArrayBufferObject::ByteLengthLimitForSmallBuffer;
#else
  // Large ArrayBuffers are not supported on 32-bit.
  static_assert(ArrayBufferObject::ByteLengthLimit ==
                ArrayBufferObject::ByteLengthLimitForSmallBuffer);
  return false;
#endif
}

JS_PUBLIC_API bool JS::IsResizableArrayBufferMaybeShared(JSObject* obj) {
  obj = UnwrapArrayBufferMaybeShared(obj);
  MOZ_ASSERT(obj);

  if (obj->is<ArrayBufferObject>()) {
    return obj->as<ArrayBufferObject>().isResizable();
  }
  return obj->as<SharedArrayBufferObject>().isGrowable();
}