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55 lines
1.1 KiB
C++
55 lines
1.1 KiB
C++
#pragma once
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#include <DB/Core/Types.h>
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#include <DB/Common/BitHelpers.h>
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namespace DB
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{
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namespace UTF8
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{
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static const UInt8 CONTINUATION_OCTET_MASK = 0b11000000u;
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static const UInt8 CONTINUATION_OCTET = 0b10000000u;
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/// return true if `octet` binary repr starts with 10 (octet is a UTF-8 sequence continuation)
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inline bool isContinuationOctet(const UInt8 octet)
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{
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return (octet & CONTINUATION_OCTET_MASK) == CONTINUATION_OCTET;
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}
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/// moves `s` backward until either first non-continuation octet or begin
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inline void syncBackward(const UInt8 * & s, const UInt8 * const begin)
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{
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while (isContinuationOctet(*s) && s > begin)
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--s;
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}
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/// moves `s` forward until either first non-continuation octet or string end is met
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inline void syncForward(const UInt8 * & s, const UInt8 * const end)
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{
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while (s < end && isContinuationOctet(*s))
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++s;
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}
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/// returns UTF-8 code point sequence length judging by it's first octet
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inline std::size_t seqLength(const UInt8 first_octet)
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{
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if (first_octet < 0x80u)
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return 1;
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const std::size_t bits = 8;
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const auto first_zero = bit_scan_reverse(static_cast<UInt8>(~first_octet));
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return bits - 1 - first_zero;
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}
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}
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}
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