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src: simplify toggling the buffer zero-fill flag #43537

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src: simplify toggling the buffer zero-fill flag #43537

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7 changes: 0 additions & 7 deletions lib/internal/bootstrap/pre_execution.js
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,6 @@ const {
getEmbedderOptions,
refreshOptions,
} = require('internal/options');
const { reconnectZeroFillToggle } = require('internal/buffer');
const {
defineOperation,
emitExperimentalWarning,
Expand All @@ -30,12 +29,6 @@ const assert = require('internal/assert');

function prepareMainThreadExecution(expandArgv1 = false,
initialzeModules = true) {
refreshRuntimeOptions();

// TODO(joyeecheung): this is also necessary for workers when they deserialize
// this toggle from the snapshot.
reconnectZeroFillToggle();

// Patch the process object with legacy properties and normalizations
patchProcessObject(expandArgv1);
setupTraceCategoryState();
Expand Down
16 changes: 3 additions & 13 deletions lib/internal/buffer.js
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Expand Up @@ -30,7 +30,7 @@ const {
hexWrite,
ucs2Write,
utf8Write,
getZeroFillToggle
setZeroFillToggle
} = internalBinding('buffer');
const {
untransferable_object_private_symbol,
Expand Down Expand Up @@ -1055,30 +1055,20 @@ function markAsUntransferable(obj) {
// in C++.
// |zeroFill| can be undefined when running inside an isolate where we
// do not own the ArrayBuffer allocator. Zero fill is always on in that case.
let zeroFill = getZeroFillToggle();
function createUnsafeBuffer(size) {
zeroFill[0] = 0;
setZeroFillToggle(false);
try {
return new FastBuffer(size);
} finally {
zeroFill[0] = 1;
setZeroFillToggle(true)
}
}

// The connection between the JS land zero fill toggle and the
// C++ one in the NodeArrayBufferAllocator gets lost if the toggle
// is deserialized from the snapshot, because V8 owns the underlying
// memory of this toggle. This resets the connection.
function reconnectZeroFillToggle() {
zeroFill = getZeroFillToggle();
}

module.exports = {
FastBuffer,
addBufferPrototypeMethods,
markAsUntransferable,
createUnsafeBuffer,
readUInt16BE,
readUInt32BE,
reconnectZeroFillToggle
};
29 changes: 5 additions & 24 deletions src/node_buffer.cc
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Expand Up @@ -1186,33 +1186,14 @@ void SetBufferPrototype(const FunctionCallbackInfo<Value>& args) {
env->set_buffer_prototype_object(proto);
}

void GetZeroFillToggle(const FunctionCallbackInfo<Value>& args) {
void SetZeroFillToggle(const FunctionCallbackInfo<Value>& args) {
Environment* env = Environment::GetCurrent(args);
NodeArrayBufferAllocator* allocator = env->isolate_data()->node_allocator();
Local<ArrayBuffer> ab;
// It can be a nullptr when running inside an isolate where we
// do not own the ArrayBuffer allocator.
if (allocator == nullptr) {
// Create a dummy Uint32Array - the JS land can only toggle the C++ land
// setting when the allocator uses our toggle. With this the toggle in JS
// land results in no-ops.
ab = ArrayBuffer::New(env->isolate(), sizeof(uint32_t));
} else {
if (allocator != nullptr) {
uint32_t* zero_fill_field = allocator->zero_fill_field();
std::unique_ptr<BackingStore> backing =
ArrayBuffer::NewBackingStore(zero_fill_field,
sizeof(*zero_fill_field),
[](void*, size_t, void*) {},
nullptr);
ab = ArrayBuffer::New(env->isolate(), std::move(backing));
*zero_fill_field = args[0]->BooleanValue(env->isolate());
}

ab->SetPrivate(
env->context(),
env->untransferable_object_private_symbol(),
True(env->isolate())).Check();

args.GetReturnValue().Set(Uint32Array::New(ab, 0, 1));
}

void DetachArrayBuffer(const FunctionCallbackInfo<Value>& args) {
Expand Down Expand Up @@ -1321,7 +1302,7 @@ void Initialize(Local<Object> target,
env->SetMethod(target, "ucs2Write", StringWrite<UCS2>);
env->SetMethod(target, "utf8Write", StringWrite<UTF8>);

env->SetMethod(target, "getZeroFillToggle", GetZeroFillToggle);
env->SetMethod(target, "setZeroFillToggle", SetZeroFillToggle);
}

} // anonymous namespace
Expand Down Expand Up @@ -1361,7 +1342,7 @@ void RegisterExternalReferences(ExternalReferenceRegistry* registry) {
registry->Register(StringWrite<HEX>);
registry->Register(StringWrite<UCS2>);
registry->Register(StringWrite<UTF8>);
registry->Register(GetZeroFillToggle);
registry->Register(SetZeroFillToggle);

registry->Register(DetachArrayBuffer);
registry->Register(CopyArrayBuffer);
Expand Down