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https://github.com/RGBCube/serenity
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AK: Replace UTF-8 string validation with a constexpr implementation
This will allow validating UTF-8 strings at compile time, such as from String::from_utf8_short_string.
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parent
f6f62d7ff6
commit
796a615bc1
2 changed files with 91 additions and 78 deletions
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@ -7,6 +7,7 @@
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#pragma once
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#include <AK/CharacterTypes.h>
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#include <AK/DeprecatedString.h>
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#include <AK/Format.h>
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#include <AK/StringView.h>
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@ -105,13 +106,6 @@ public:
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return byte_offset_of(it);
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}
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bool validate(size_t& valid_bytes) const;
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bool validate() const
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{
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size_t valid_bytes;
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return validate(valid_bytes);
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}
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size_t length() const
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{
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if (!m_have_length) {
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@ -121,11 +115,99 @@ public:
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return m_length;
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}
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constexpr bool validate() const
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{
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size_t valid_bytes = 0;
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return validate(valid_bytes);
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}
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constexpr bool validate(size_t& valid_bytes) const
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{
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valid_bytes = 0;
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for (auto it = m_string.begin(); it != m_string.end(); ++it) {
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auto [byte_length, code_point, is_valid] = decode_leading_byte(static_cast<u8>(*it));
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if (!is_valid)
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return false;
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for (size_t i = 1; i < byte_length; ++i) {
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if (++it == m_string.end())
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return false;
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auto [code_point_bits, is_valid] = decode_continuation_byte(static_cast<u8>(*it));
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if (!is_valid)
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return false;
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code_point <<= 6;
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code_point |= code_point_bits;
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}
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if (!is_unicode(code_point))
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return false;
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valid_bytes += byte_length;
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}
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return true;
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}
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private:
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friend class Utf8CodePointIterator;
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u8 const* begin_ptr() const { return (u8 const*)m_string.characters_without_null_termination(); }
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u8 const* end_ptr() const { return begin_ptr() + m_string.length(); }
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size_t calculate_length() const;
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struct Utf8EncodedByteData {
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size_t byte_length { 0 };
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u8 encoding_bits { 0 };
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u8 encoding_mask { 0 };
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};
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static constexpr Array<Utf8EncodedByteData, 4> utf8_encoded_byte_data { {
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{ 1, 0b0000'0000, 0b1000'0000 },
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{ 2, 0b1100'0000, 0b1110'0000 },
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{ 3, 0b1110'0000, 0b1111'0000 },
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{ 4, 0b1111'0000, 0b1111'1000 },
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} };
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struct LeadingByte {
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size_t byte_length { 0 };
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u32 code_point_bits { 0 };
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bool is_valid { false };
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};
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static constexpr LeadingByte decode_leading_byte(u8 byte)
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{
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for (auto const& data : utf8_encoded_byte_data) {
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if ((byte & data.encoding_mask) != data.encoding_bits)
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continue;
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byte &= ~data.encoding_mask;
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return { data.byte_length, byte, true };
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}
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return { .is_valid = false };
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}
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struct ContinuationByte {
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u32 code_point_bits { 0 };
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bool is_valid { false };
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};
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static constexpr ContinuationByte decode_continuation_byte(u8 byte)
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{
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constexpr u8 continuation_byte_encoding_bits = 0b1000'0000;
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constexpr u8 continuation_byte_encoding_mask = 0b1100'0000;
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if ((byte & continuation_byte_encoding_mask) == continuation_byte_encoding_bits) {
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byte &= ~continuation_byte_encoding_mask;
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return { byte, true };
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}
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return { .is_valid = false };
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}
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StringView m_string;
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mutable size_t m_length { 0 };
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mutable bool m_have_length { false };
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