Goの標準のutf8.RuneStart関数がエレガントすぎる
先日以下の記事を書きました。 ここでUTF-8の最初の文字かどうかの判定を以下の自作した関数で実装していました。 const ( t1 = 0b00000000 tx = 0b10000000 t2 = 0b00000110 t3 = 0b00001110 t4 = 0b00011110 ) func isUTF8LeadByte(tmp byte) bool { if tmp&tx == t1 { return true } tmp >>= 3 if tmp == t4 { return true } tmp >>= 1 if tmp == t3 { return true } tmp >>= 1 if tmp == t2 { return true } return false }
Decoding UTF8 with Parallel Extract
Decoding UTF8 with Parallel Extract 23 Mar 2024 As a side-quest I recently decided to write a branchless utf8 decoder utilizing the pext or "parallel extract" instruction. It's compliant with rfc-3629, meaning that it doesn't just naively decode the code-point but also checks for overlong encoding, surrogate pairs and such. Compiled with gcc -O3 -march=x86-64-v3 the entire decoder results in just
UTF-8のバリデーションとモノイドと半群
この記事はUTF-8のバリデーションとオートマトンの続きです。 前回はUTF-8のバリデーションが8状態のオートマトン (DFA) で表現できることを見ました。状態と遷移を擬似コードで書けば次のようになるでしょう： -- 8つの状態 data State = START | TAILx1 | TAILx2 | TAILx3 | A | B | C | D -- 入力バイトに応じて次の状態を返す。次の状態が該当しなかったら Nothing を返す next :: Word8 -> State -> Maybe State +----+----+-----+----+ | a0 | a1 | ... | aN | 8ビット整数列 +----+----+-----+----+ | | | v v v +----+----+-----+----+ | m0 | m1 | ... | mN | モノ
So Long Surrogates: How we moved to UTF-8 in Haskell
We released a blazingly fast Aho-Corasick implementation, written in Haskell, in 2019. This implementation was based on UTF-16 strings, since Haskell's text library uses that for its internal string representation. However, the most recent major update of text changed its internal string representation from UTF-16 to UTF-8. This is good news for us, since most of our customer’s data is ASCII, this
How does UTF-8 turn “😂” into “F09F9882”?
More often than not the mechanism being used to turn bytes into characters and emojis on your computer is "UTF-8". I recently learned how UTF-8 works and felt that the definition lended itself perfectly to creating diagrams explaining the implementation. I created these diagrams for my own enjoyment and wanted to share them. Hopefully this will inspire you to learn how other low-level protocols wo
UTF-8をデコードするオートマトンの実装 - Qiita
オートマトンを実装するための方法として、ある状態において、どの文字を受け取ったら、次の状態がどれであるかを表で表現する事ができます。今入力として1バイト受け取ることを考えると、1バイトは0-255の256通りなので、状態を整数で表すとして、以下のように2次元配列で表現できます。 static const signed char trans[][0x100] = { { /* S0 0 1 2 3 4 5 6 7 8 9 a b c d e f */ /* 0 */ A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, /* 1 */ A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, /* 2 */ A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, A, /* 3
Decoding UTF-8 with Parser Combinators
Now let’s talk about what it means. First, note that 0xxxxxxx is not hexadecimal, but a bit pattern that means the “control” bit 0 followed by seven “data” bits, which could be anything. The four rows in the table correspond to the four flavors of UTF-8 codepoints, distinguished by the number of bytes you need to encode them (one to four). “Lower bound” and “upper bound” tell us which codepoints l
1
リリース、障害情報などのサービスのお知らせ
最新の人気エントリーの配信
j次のブックマーク
k前のブックマーク
lあとで読む
eコメント一覧を開く
oページを開く
GitHub - zwegner/faster-utf8-validator: A very fast library for validating UTF-8 using AVX2/SSE4 instructions
UTF-8 String Indexing Strategies