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LibTextCodec: Use AK facilities to validate and convert UTF-16 to UTF-8

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This allows LibTextCodec to make use of simdutf, and also reduces the
number of places with manual UTF-16 implementations.
This commit is contained in:
Timothy Flynn 2024-07-18 12:07:37 -04:00 committed by Andreas Kling
parent 71c29504af
commit 368dad54ef
Notes: sideshowbarker 2024-07-19 06:22:43 +09:00 
Author: https://github.com/trflynn89
Commit: https://github.com/LadybirdBrowser/ladybird/commit/368dad54ef2
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/698
2 changed files with 30 additions and 112 deletions
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12
Tests/LibTextCodec/TestTextDecoders.cpp
View file

@ -15,6 +15,8 @@ TEST_CASE(test_utf8_decode)
// Bytes for U+1F600 GRINNING FACE
auto test_string = "\xf0\x9f\x98\x80"sv;
EXPECT(decoder.validate(test_string));
Vector<u32> processed_code_points;
MUST(decoder.process(test_string, [&](u32 code_point) {
return processed_code_points.try_append(code_point);
@ -31,6 +33,8 @@ TEST_CASE(test_utf16be_decode)
// This is the output of `python3 -c "print('säk😀'.encode('utf-16be'))"`.
auto test_string = "\x00s\x00\xe4\x00k\xd8=\xde\x00"sv;
EXPECT(decoder.validate(test_string));
Vector<u32> processed_code_points;
MUST(decoder.process(test_string, [&](u32 code_point) {
return processed_code_points.try_append(code_point);
@ -40,6 +44,9 @@ TEST_CASE(test_utf16be_decode)
EXPECT(processed_code_points[1] == 0xE4);
EXPECT(processed_code_points[2] == 0x6B);
EXPECT(processed_code_points[3] == 0x1F600);
auto utf8 = MUST(decoder.to_utf8(test_string));
EXPECT_EQ(utf8, "säk😀"sv);
}
TEST_CASE(test_utf16le_decode)
@ -48,6 +55,8 @@ TEST_CASE(test_utf16le_decode)
// This is the output of `python3 -c "print('säk😀'.encode('utf-16le'))"`.
auto test_string = "s\x00\xe4\x00k\x00=\xd8\x00\xde"sv;
EXPECT(decoder.validate(test_string));
Vector<u32> processed_code_points;
MUST(decoder.process(test_string, [&](u32 code_point) {
return processed_code_points.try_append(code_point);
@ -57,4 +66,7 @@ TEST_CASE(test_utf16le_decode)
EXPECT(processed_code_points[1] == 0xE4);
EXPECT(processed_code_points[2] == 0x6B);
EXPECT(processed_code_points[3] == 0x1F600);
auto utf8 = MUST(decoder.to_utf8(test_string));
EXPECT_EQ(utf8, "säk😀"sv);
}

130
Userland/Libraries/LibTextCodec/Decoder.cpp
View file

@ -375,150 +375,56 @@ ErrorOr<String> UTF8Decoder::to_utf8(StringView input)
return Decoder::to_utf8(bomless_input);
}
static Utf16View as_utf16(StringView view, AK::Endianness endianness)
{
return Utf16View {
{ reinterpret_cast<u16 const*>(view.bytes().data()), view.length() / 2 },
endianness
};
}
ErrorOr<void> UTF16BEDecoder::process(StringView input, Function<ErrorOr<void>(u32)> on_code_point)
{
// rfc2781, 2.2 Decoding UTF-16
size_t utf16_length = input.length() - (input.length() % 2);
for (size_t i = 0; i < utf16_length; i += 2) {
// 1) If W1 < 0xD800 or W1 > 0xDFFF, the character value U is the value
// of W1. Terminate.
u16 w1 = (static_cast<u8>(input[i]) << 8) | static_cast<u8>(input[i + 1]);
if (!is_unicode_surrogate(w1)) {
TRY(on_code_point(w1));
continue;
}
// 2) Determine if W1 is between 0xD800 and 0xDBFF. If not, the sequence
// is in error and no valid character can be obtained using W1.
// Terminate.
// 3) If there is no W2 (that is, the sequence ends with W1), or if W2
// is not between 0xDC00 and 0xDFFF, the sequence is in error.
// Terminate.
if (!Utf16View::is_high_surrogate(w1) || i + 2 == utf16_length) {
TRY(on_code_point(replacement_code_point));
continue;
}
u16 w2 = (static_cast<u8>(input[i + 2]) << 8) | static_cast<u8>(input[i + 3]);
if (!Utf16View::is_low_surrogate(w2)) {
TRY(on_code_point(replacement_code_point));
continue;
}
// 4) Construct a 20-bit unsigned integer U', taking the 10 low-order
// bits of W1 as its 10 high-order bits and the 10 low-order bits of
// W2 as its 10 low-order bits.
// 5) Add 0x10000 to U' to obtain the character value U. Terminate.
TRY(on_code_point(Utf16View::decode_surrogate_pair(w1, w2)));
i += 2;
}
for (auto code_point : as_utf16(input, AK::Endianness::Big))
TRY(on_code_point(code_point));
return {};
}
bool UTF16BEDecoder::validate(StringView input)
{
size_t utf16_length = input.length() - (input.length() % 2);
for (size_t i = 0; i < utf16_length; i += 2) {
u16 w1 = (static_cast<u8>(input[i]) << 8) | static_cast<u8>(input[i + 1]);
if (!is_unicode_surrogate(w1))
continue;
if (!Utf16View::is_high_surrogate(w1) || i + 2 == utf16_length)
return false;
u16 w2 = (static_cast<u8>(input[i + 2]) << 8) | static_cast<u8>(input[i + 3]);
if (!Utf16View::is_low_surrogate(w2))
return false;
i += 2;
}
return true;
return as_utf16(input, AK::Endianness::Big).validate();
}
ErrorOr<String> UTF16BEDecoder::to_utf8(StringView input)
{
// Discard the BOM
auto bomless_input = input;
if (auto bytes = input.bytes(); bytes.size() >= 2 && bytes[0] == 0xFE && bytes[1] == 0xFF)
bomless_input = input.substring_view(2);
input = input.substring_view(2);
StringBuilder builder(bomless_input.length() / 2);
TRY(process(bomless_input, [&builder](u32 c) { return builder.try_append_code_point(c); }));
return builder.to_string();
return String::from_utf16(as_utf16(input, AK::Endianness::Big));
}
ErrorOr<void> UTF16LEDecoder::process(StringView input, Function<ErrorOr<void>(u32)> on_code_point)
{
// rfc2781, 2.2 Decoding UTF-16
size_t utf16_length = input.length() - (input.length() % 2);
for (size_t i = 0; i < utf16_length; i += 2) {
// 1) If W1 < 0xD800 or W1 > 0xDFFF, the character value U is the value
// of W1. Terminate.
u16 w1 = static_cast<u8>(input[i]) | (static_cast<u8>(input[i + 1]) << 8);
if (!is_unicode_surrogate(w1)) {
TRY(on_code_point(w1));
continue;
}
// 2) Determine if W1 is between 0xD800 and 0xDBFF. If not, the sequence
// is in error and no valid character can be obtained using W1.
// Terminate.
// 3) If there is no W2 (that is, the sequence ends with W1), or if W2
// is not between 0xDC00 and 0xDFFF, the sequence is in error.
// Terminate.
if (!Utf16View::is_high_surrogate(w1) || i + 2 == utf16_length) {
TRY(on_code_point(replacement_code_point));
continue;
}
u16 w2 = static_cast<u8>(input[i + 2]) | (static_cast<u8>(input[i + 3]) << 8);
if (!Utf16View::is_low_surrogate(w2)) {
TRY(on_code_point(replacement_code_point));
continue;
}
// 4) Construct a 20-bit unsigned integer U', taking the 10 low-order
// bits of W1 as its 10 high-order bits and the 10 low-order bits of
// W2 as its 10 low-order bits.
// 5) Add 0x10000 to U' to obtain the character value U. Terminate.
TRY(on_code_point(Utf16View::decode_surrogate_pair(w1, w2)));
i += 2;
}
for (auto code_point : as_utf16(input, AK::Endianness::Little))
TRY(on_code_point(code_point));
return {};
}
bool UTF16LEDecoder::validate(StringView input)
{
size_t utf16_length = input.length() - (input.length() % 2);
for (size_t i = 0; i < utf16_length; i += 2) {
u16 w1 = static_cast<u8>(input[i]) | (static_cast<u8>(input[i + 1]) << 8);
if (!is_unicode_surrogate(w1))
continue;
if (!Utf16View::is_high_surrogate(w1) || i + 2 == utf16_length)
return false;
u16 w2 = static_cast<u8>(input[i + 2]) | (static_cast<u8>(input[i + 3]) << 8);
if (!Utf16View::is_low_surrogate(w2))
return false;
i += 2;
}
return true;
return as_utf16(input, AK::Endianness::Little).validate();
}
ErrorOr<String> UTF16LEDecoder::to_utf8(StringView input)
{
// Discard the BOM
auto bomless_input = input;
if (auto bytes = input.bytes(); bytes.size() >= 2 && bytes[0] == 0xFF && bytes[1] == 0xFE)
bomless_input = input.substring_view(2);
input = input.substring_view(2);
StringBuilder builder(bomless_input.length() / 2);
TRY(process(bomless_input, [&builder](u32 c) { return builder.try_append_code_point(c); }));
return builder.to_string();
return String::from_utf16(as_utf16(input, AK::Endianness::Little));
}
ErrorOr<void> Latin1Decoder::process(StringView input, Function<ErrorOr<void>(u32)> on_code_point)