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…d surrogate characters
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やったー |
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私Java読めませんけど？🫠 |
Siro256
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Jan 28, 2026
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| private static int calcBufferLength(String src) { | ||
| int srcCodePointCount = src.codePointCount(0, src.length()); | ||
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| int offset = src.offsetByCodePoints(0, srcCodePointCount - 1); | ||
| int lastCodePoint = src.codePointAt(offset); | ||
| boolean isSevenBitsCode = lastCodePoint <= SEVEN_BITS_CP_FINAL; | ||
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| return (isSevenBitsCode ? (srcCodePointCount - 1) * 15 + 7 : srcCodePointCount * 15) / 8; | ||
| } |
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文字を総舐めしてcp数を数えるより、入力された文字が正しいBase32768エンコーディングであると仮定して文字数からバッファ長を計算したほうが良いかもしれない？
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| final int n = src.length(); | ||
| if (n == 0) return new byte[0]; | ||
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| int srcCodePointCount = src.codePointCount(0, src.length()); | ||
| byte[] bytes = new byte[calcBufferLength(src)]; | ||
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| // Multithread-safeではない | ||
| final var ref = new Object() { | ||
| int srcIndex = 0; | ||
| int dstIndex = 0; | ||
| int buf = 0; | ||
| int bufCount = 0; | ||
| }; | ||
| src.codePoints().forEachOrdered(codePoint -> { | ||
| Integer byteBase = TABLE.get(codePoint & ~31); | ||
| if (byteBase == null) throw new IllegalBase32768TextException(ref.srcIndex + 1, codePoint); | ||
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| if (codePoint <= SEVEN_BITS_CP_FINAL) { | ||
| if (ref.srcIndex != srcCodePointCount - 1) throw new IllegalBase32768TextException(codePoint); | ||
| ref.buf = (ref.buf << 7) + byteBase + codePoint % 32; | ||
| ref.bufCount += 7; | ||
| } else { | ||
| ref.buf = (ref.buf << 15) + byteBase + codePoint % 32; | ||
| ref.bufCount += 15; | ||
| final char last = src.charAt(n - 1); | ||
| final int lastBits = LAST_BITS[last] & 0xFF; | ||
| if (lastBits == 0) throw new IllegalBase32768TextException(n - 1, last); | ||
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| final int outLen = ((n - 1) * 15 + lastBits) >>> 3; |
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これをcalcBufferLengthの実装にすると良いかもしれません？
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calcBufferLengthと同じ実装になりましたが、そもそもの実装が意図していないものだったらこちらも同様かもしれません
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| private static final char[] DECODE = new char[1 << 16]; | ||
| private static final byte[] LAST_BITS = new byte[1 << 16]; |
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15bits範囲と7bits範囲のテーブルを分けると、テーブルサイズが2^17から2^11 + 2^8に削減できそうな気がします
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とりあえず変更量が少なくて済む方法としてDECODEのサイズを削れるだけ削ってみました。これで分割とほぼ同じ削減量を得られる気がしますがどうでしょうか🤔
LAST_BITSはブロック単位にして、大幅削減しました。シフト演算が1回増えるけどパフォーマンスへの影響は誤差の範囲なはずです
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なんで最初からこうしなかったのかは不明なんですが、それはそうと破壊してないか不安です
テストは通ってますが...
Co-authored-by: Siro / MIYAGI Naoki <[email protected]>
…r length calculation
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