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745b998774
The spec version of canonical_numeric_index_string is absurdly complex, and ends up converting from a string to a number, and then back again which is both slow and also requires a few allocations and a string compare. Instead this patch moves away from using Values to represent canonical a canonical index. In most cases all we need to know is whether a PropertyKey is an integer between 0 and 2^^32-2, which we already compute when we construct a PropertyKey so the existing is_number() check is sufficient. The more expensive case is handling strings containing numbers that don't roundtrip through string conversion. In most cases these turn into regular string properties, but for TypedArray access these property names are not treated as normal named properties. TypedArrays treat these numeric properties as magic indexes that are ignored on read and are not stored (but are evaluated) on assignment. For that reason there's now a mode flag on canonical_numeric_index_string so that only TypedArrays take the cost of the ToString round trip test. In order to improve the performance of this path this patch includes some early returns to avoid conversion in cases where we can quickly know whether a property can round trip.
86 lines
3.1 KiB
C++
86 lines
3.1 KiB
C++
/*
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* Copyright (c) 2021, Luke Wilde <lukew@serenityos.org>
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* Copyright (c) 2021, Linus Groh <linusg@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/ByteBuffer.h>
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#include <AK/NumericLimits.h>
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#include <LibJS/Runtime/AbstractOperations.h>
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#include <LibJS/Runtime/ArrayBuffer.h>
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#include <LibJS/Runtime/DataView.h>
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#include <LibJS/Runtime/PropertyKey.h>
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#include <LibJS/Runtime/TypedArray.h>
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#include <LibWeb/Bindings/IDLAbstractOperations.h>
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namespace Web::Bindings::IDL {
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// https://webidl.spec.whatwg.org/#dfn-get-buffer-source-copy
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Optional<ByteBuffer> get_buffer_source_copy(JS::Object const& buffer_source)
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{
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// 1. Let esBufferSource be the result of converting bufferSource to an ECMAScript value.
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// 2. Let esArrayBuffer be esBufferSource.
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JS::ArrayBuffer* es_array_buffer;
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// 3. Let offset be 0.
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u32 offset = 0;
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// 4. Let length be 0.
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u32 length = 0;
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// 5. If esBufferSource has a [[ViewedArrayBuffer]] internal slot, then:
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if (is<JS::TypedArrayBase>(buffer_source)) {
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auto const& es_buffer_source = static_cast<JS::TypedArrayBase const&>(buffer_source);
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// 1. Set esArrayBuffer to esBufferSource.[[ViewedArrayBuffer]].
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es_array_buffer = es_buffer_source.viewed_array_buffer();
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// 2. Set offset to esBufferSource.[[ByteOffset]].
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offset = es_buffer_source.byte_offset();
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// 3. Set length to esBufferSource.[[ByteLength]].
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length = es_buffer_source.byte_length();
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} else if (is<JS::DataView>(buffer_source)) {
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auto const& es_buffer_source = static_cast<JS::DataView const&>(buffer_source);
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// 1. Set esArrayBuffer to esBufferSource.[[ViewedArrayBuffer]].
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es_array_buffer = es_buffer_source.viewed_array_buffer();
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// 2. Set offset to esBufferSource.[[ByteOffset]].
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offset = es_buffer_source.byte_offset();
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// 3. Set length to esBufferSource.[[ByteLength]].
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length = es_buffer_source.byte_length();
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}
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// 6. Otherwise:
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else {
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// 1. Assert: esBufferSource is an ArrayBuffer or SharedArrayBuffer object.
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auto const& es_buffer_source = static_cast<JS::ArrayBuffer const&>(buffer_source);
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es_array_buffer = &const_cast<JS ::ArrayBuffer&>(es_buffer_source);
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// 2. Set length to esBufferSource.[[ArrayBufferByteLength]].
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length = es_buffer_source.byte_length();
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}
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// 7. If ! IsDetachedBuffer(esArrayBuffer) is true, then return the empty byte sequence.
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if (es_array_buffer->is_detached())
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return ByteBuffer {};
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// 8. Let bytes be a new byte sequence of length equal to length.
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auto bytes = ByteBuffer::create_zeroed(length);
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if (bytes.is_error())
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return {};
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// 9. For i in the range offset to offset + length − 1, inclusive, set bytes[i − offset] to ! GetValueFromBuffer(esArrayBuffer, i, Uint8, true, Unordered).
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for (u64 i = offset; i <= offset + length - 1; ++i) {
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auto value = es_array_buffer->get_value<u8>(i, true, JS::ArrayBuffer::Unordered);
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bytes.value()[i - offset] = (u8)value.as_u32();
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}
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// 10. Return bytes.
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return bytes.release_value();
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}
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}
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