0c42aece36
LibJS parses JavaScript as UTF-8, so when creating a string, we must
transcode it to UTF-16 to handle encoded surrogate pairs.
For example, consider the following string:
"\ud83d\ude00"
The UTF-8 encoding of this surrogate pair is:
0xf0 0x9f 0x98 0x80
However, LibJS will currently store the two surrogates individually as
UTF-8 encoded bytes, rather than combining the pair:
0xed 0xa0 0xb8, 0xed 0xb8 0x80
These are not equivalent. So, as String.prototype becomes UTF-16 aware,
this encoding will no longer work for abstractions like strict equality.
85 lines
2.3 KiB
C++
85 lines
2.3 KiB
C++
/*
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* Copyright (c) 2020, Andreas Kling <kling@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/CharacterTypes.h>
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#include <AK/Utf16View.h>
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#include <LibJS/Runtime/PrimitiveString.h>
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#include <LibJS/Runtime/VM.h>
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namespace JS {
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PrimitiveString::PrimitiveString(String string)
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: m_string(move(string))
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{
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}
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PrimitiveString::~PrimitiveString()
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{
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}
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Vector<u16> const& PrimitiveString::utf16_string() const
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{
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if (m_utf16_string.is_empty() && !m_string.is_empty())
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m_utf16_string = AK::utf8_to_utf16(m_string);
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return m_utf16_string;
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}
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Utf16View PrimitiveString::utf16_string_view() const
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{
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return Utf16View { utf16_string() };
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}
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PrimitiveString* js_string(Heap& heap, Utf16View const& string)
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{
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if (string.is_empty())
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return &heap.vm().empty_string();
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if (string.length_in_code_units() == 1) {
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u16 code_unit = string.code_unit_at(0);
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if (is_ascii(code_unit))
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return &heap.vm().single_ascii_character_string(static_cast<u8>(code_unit));
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}
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auto utf8_string = string.to_utf8(Utf16View::AllowInvalidCodeUnits::Yes);
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return heap.allocate_without_global_object<PrimitiveString>(move(utf8_string));
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}
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PrimitiveString* js_string(VM& vm, Utf16View const& string)
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{
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return js_string(vm.heap(), string);
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}
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PrimitiveString* js_string(Heap& heap, String string)
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{
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if (string.is_empty())
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return &heap.vm().empty_string();
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if (string.length() == 1) {
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auto ch = static_cast<u8>(string.characters()[0]);
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if (is_ascii(ch))
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return &heap.vm().single_ascii_character_string(ch);
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}
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// UTF-8 strings must first be transcoded to UTF-16, even though they are stored as String objects
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// internally, to parse encoded surrogate pairs. As an optimization to reduce string copying, only
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// perform that transcoding if there are non-ASCII codepoints in the string.
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for (auto it : string) {
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auto ch = static_cast<u8>(it);
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if (!is_ascii(ch)) {
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auto utf16_string = AK::utf8_to_utf16(string);
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return js_string(heap, Utf16View { utf16_string });
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}
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}
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return heap.allocate_without_global_object<PrimitiveString>(move(string));
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}
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PrimitiveString* js_string(VM& vm, String string)
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{
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return js_string(vm.heap(), move(string));
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}
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}
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