static inline JSC::EncodedJSValue flattenArrayOfBuffersIntoArrayBufferOrUint8Array()

in src/bun.js/bindings/BunObject.cpp [71:213]
120 lines of code
23 McCabe index (conditional complexity)

static inline JSC::EncodedJSValue flattenArrayOfBuffersIntoArrayBufferOrUint8Array(JSGlobalObject* lexicalGlobalObject, JSValue arrayValue, size_t maxLength, bool asUint8Array)
{
    auto& vm = lexicalGlobalObject->vm();

    if (arrayValue.isUndefinedOrNull() || !arrayValue) {
        return JSC::JSValue::encode(JSC::JSArrayBuffer::create(vm, lexicalGlobalObject->arrayBufferStructure(), JSC::ArrayBuffer::create(static_cast<size_t>(0), 1)));
    }

    auto throwScope = DECLARE_THROW_SCOPE(vm);

    auto array = JSC::jsDynamicCast<JSC::JSArray*>(arrayValue);
    if (UNLIKELY(!array)) {
        throwTypeError(lexicalGlobalObject, throwScope, "Argument must be an array"_s);
        return JSValue::encode(jsUndefined());
    }

    size_t arrayLength = array->length();
    const auto returnEmptyArrayBufferView = [&]() -> EncodedJSValue {
        if (asUint8Array) {
            return JSValue::encode(
                JSC::JSUint8Array::create(
                    lexicalGlobalObject,
                    lexicalGlobalObject->m_typedArrayUint8.get(lexicalGlobalObject),
                    0));
        }

        RELEASE_AND_RETURN(throwScope, JSValue::encode(JSC::JSArrayBuffer::create(vm, lexicalGlobalObject->arrayBufferStructure(), JSC::ArrayBuffer::create(static_cast<size_t>(0), 1))));
    };

    if (arrayLength < 1) {
        return returnEmptyArrayBufferView();
    }

    size_t byteLength = 0;
    bool any_buffer = false;
    bool any_typed = false;

    // Use an argument buffer to avoid calling `getIndex` more than once per element.
    // This is a small optimization
    MarkedArgumentBuffer args;
    args.ensureCapacity(arrayLength);
    if (UNLIKELY(args.hasOverflowed())) {
        throwOutOfMemoryError(lexicalGlobalObject, throwScope);
        return JSValue::encode({});
    }

    for (size_t i = 0; i < arrayLength; i++) {
        auto element = array->getIndex(lexicalGlobalObject, i);
        RETURN_IF_EXCEPTION(throwScope, {});

        if (auto* typedArray = JSC::jsDynamicCast<JSC::JSArrayBufferView*>(element)) {
            if (UNLIKELY(typedArray->isDetached())) {
                throwTypeError(lexicalGlobalObject, throwScope, "ArrayBufferView is detached"_s);
                return JSValue::encode(jsUndefined());
            }
            size_t current = typedArray->byteLength();
            any_typed = true;
            byteLength += current;

            if (current > 0) {
                args.append(typedArray);
            }
        } else if (auto* arrayBuffer = JSC::jsDynamicCast<JSC::JSArrayBuffer*>(element)) {
            auto* impl = arrayBuffer->impl();
            if (UNLIKELY(!impl)) {
                throwTypeError(lexicalGlobalObject, throwScope, "ArrayBuffer is detached"_s);
                return JSValue::encode(jsUndefined());
            }

            size_t current = impl->byteLength();
            any_buffer = true;

            if (current > 0) {
                args.append(arrayBuffer);
            }

            byteLength += current;
        } else {
            throwTypeError(lexicalGlobalObject, throwScope, "Expected TypedArray"_s);
            return JSValue::encode(jsUndefined());
        }
    }
    byteLength = std::min(byteLength, maxLength);

    if (byteLength == 0) {
        return returnEmptyArrayBufferView();
    }

    auto buffer = JSC::ArrayBuffer::tryCreateUninitialized(byteLength, 1);
    if (UNLIKELY(!buffer)) {
        throwTypeError(lexicalGlobalObject, throwScope, "Failed to allocate ArrayBuffer"_s);
        return JSValue::encode(jsUndefined());
    }

    size_t remain = byteLength;
    auto* head = reinterpret_cast<char*>(buffer->data());

    if (!any_buffer) {
        for (size_t i = 0; i < args.size(); i++) {
            auto element = args.at(i);
            RETURN_IF_EXCEPTION(throwScope, {});
            auto* view = JSC::jsCast<JSC::JSArrayBufferView*>(element);
            size_t length = std::min(remain, view->byteLength());
            memcpy(head, view->vector(), length);
            remain -= length;
            head += length;
        }
    } else if (!any_typed) {
        for (size_t i = 0; i < args.size(); i++) {
            auto element = args.at(i);
            RETURN_IF_EXCEPTION(throwScope, {});
            auto* view = JSC::jsCast<JSC::JSArrayBuffer*>(element);
            size_t length = std::min(remain, view->impl()->byteLength());
            memcpy(head, view->impl()->data(), length);
            remain -= length;
            head += length;
        }
    } else {
        for (size_t i = 0; i < args.size(); i++) {
            auto element = args.at(i);
            RETURN_IF_EXCEPTION(throwScope, {});
            size_t length = 0;
            if (auto* view = JSC::jsDynamicCast<JSC::JSArrayBuffer*>(element)) {
                length = std::min(remain, view->impl()->byteLength());
                memcpy(head, view->impl()->data(), length);
            } else {
                auto* typedArray = JSC::jsCast<JSC::JSArrayBufferView*>(element);
                length = std::min(remain, typedArray->byteLength());
                memcpy(head, typedArray->vector(), length);
            }

            remain -= length;
            head += length;
        }
    }

    if (asUint8Array) {
        auto uint8array = JSC::JSUint8Array::create(lexicalGlobalObject, lexicalGlobalObject->m_typedArrayUint8.get(lexicalGlobalObject), WTFMove(buffer), 0, byteLength);
        return JSValue::encode(uint8array);
    }

    RELEASE_AND_RETURN(throwScope, JSValue::encode(JSC::JSArrayBuffer::create(vm, lexicalGlobalObject->arrayBufferStructure(), WTFMove(buffer))));
}