JS_DetachArrayBuffer(JSContext* cx, HandleObject obj,
DetachDataDisposition changeData)
{
if (!obj->is<ArrayBufferObject>()) {
JS_ReportError(cx, "ArrayBuffer object required");
return false;
}
Rooted<ArrayBufferObject*> buffer(cx, &obj->as<ArrayBufferObject>());
if (changeData == ChangeData && buffer->hasStealableContents()) {
ArrayBufferObject::BufferContents newContents =
AllocateArrayBufferContents(cx, buffer->byteLength());
if (!newContents)
return false;
if (!ArrayBufferObject::detach(cx, buffer, newContents)) {
js_free(newContents.data());
return false;
}
} else {
if (!ArrayBufferObject::detach(cx, buffer, buffer->contents()))
return false;
}
return true;
}
static void
NoteViewBufferWasDetached(ArrayBufferViewObject* view,
ArrayBufferObject::BufferContents newContents,
JSContext* cx)
{
view->notifyBufferDetached(newContents.data());
// Notify compiled jit code that the base pointer has moved.
MarkObjectStateChange(cx, view);
}
static bool
TransferAsmJSMappedBuffer(JSContext* cx, const CallArgs& args,
Handle<ArrayBufferObject*> oldBuffer, size_t newByteLength)
{
size_t oldByteLength = oldBuffer->byteLength();
MOZ_ASSERT(oldByteLength % AsmJSPageSize == 0);
MOZ_ASSERT(newByteLength % AsmJSPageSize == 0);
ArrayBufferObject::BufferContents stolen =
ArrayBufferObject::stealContents(cx, oldBuffer, /* hasStealableContents = */ true);
if (!stolen)
return false;
MOZ_ASSERT(stolen.kind() == ArrayBufferObject::ASMJS_MAPPED);
uint8_t* data = stolen.data();
if (newByteLength > oldByteLength) {
void* diffStart = data + oldByteLength;
size_t diffLength = newByteLength - oldByteLength;
# ifdef XP_WIN
if (!VirtualAlloc(diffStart, diffLength, MEM_COMMIT, PAGE_READWRITE)) {
ReleaseAsmJSMappedData(data);
ReportOutOfMemory(cx);
return false;
}
# else
// To avoid memset, use MAP_FIXED to clobber the newly-accessible pages
// with zero pages.
int flags = MAP_FIXED | MAP_PRIVATE | MAP_ANON;
if (mmap(diffStart, diffLength, PROT_READ | PROT_WRITE, flags, -1, 0) == MAP_FAILED) {
ReleaseAsmJSMappedData(data);
ReportOutOfMemory(cx);
return false;
}
# endif
MemProfiler::SampleNative(diffStart, diffLength);
} else if (newByteLength < oldByteLength) {
void* diffStart = data + newByteLength;
size_t diffLength = oldByteLength - newByteLength;
# ifdef XP_WIN
if (!VirtualFree(diffStart, diffLength, MEM_DECOMMIT)) {
ReleaseAsmJSMappedData(data);
ReportOutOfMemory(cx);
return false;
}
# else
if (madvise(diffStart, diffLength, MADV_DONTNEED) ||
mprotect(diffStart, diffLength, PROT_NONE))
{
ReleaseAsmJSMappedData(data);
ReportOutOfMemory(cx);
return false;
}
# endif
}
ArrayBufferObject::BufferContents newContents =
ArrayBufferObject::BufferContents::create<ArrayBufferObject::ASMJS_MAPPED>(data);
RootedObject newBuffer(cx, ArrayBufferObject::create(cx, newByteLength, newContents));
if (!newBuffer) {
ReleaseAsmJSMappedData(data);
return false;
}
args.rval().setObject(*newBuffer);
return true;
}