Fix ByteBufUtil#writeUtf8 subsequence split surrogate edge-case bug #9437
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Motivation netty#9224 introduced overrides of ByteBufUtil#writeUtf8(...) and related methods to operate on a sub-CharSequence directly to save having to allocate substrings, but it missed an edge case where the subsequence does not extend to the end of the CharSequence and the last char in the sequence is a high surrogate. Due to the catch-IndexOutOfBoundsException optimization that avoids an additional bounds check, it would be possible to read past the specified end char index and successfully decode a surrogate pair which would otherwise result in a '?' byte being written. Modifications - Check for end-of-subsequence before reading next char after a high surrogate is encountered in the writeUtf8(AbstractByteBuf,int,CharSequence,int,int) and utf8BytesNonAscii methods - Add unit test for this edge case Result Bug is fixed. This removes the bounds-check-avoidance optimization but it does not appear to have a measurable impact on benchmark results, including when the char sequence contains many surrogate pairs (which should be rare in any case).
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Can one of the admins verify this patch? |
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@netty-bot test this please |
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@netty-bot test this please |
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@njhill thanks a lot! |
normanmaurer
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Aug 10, 2019
…9437) Motivation: #9224 introduced overrides of ByteBufUtil#writeUtf8(...) and related methods to operate on a sub-CharSequence directly to save having to allocate substrings, but it missed an edge case where the subsequence does not extend to the end of the CharSequence and the last char in the sequence is a high surrogate. Due to the catch-IndexOutOfBoundsException optimization that avoids an additional bounds check, it would be possible to read past the specified end char index and successfully decode a surrogate pair which would otherwise result in a '?' byte being written. Modifications: - Check for end-of-subsequence before reading next char after a high surrogate is encountered in the writeUtf8(AbstractByteBuf,int,CharSequence,int,int) and utf8BytesNonAscii methods - Add unit test for this edge case Result: Bug is fixed. This removes the bounds-check-avoidance optimization but it does not appear to have a measurable impact on benchmark results, including when the char sequence contains many surrogate pairs (which should be rare in any case).
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Motivation
#9224 introduced overloads of
ByteBufUtil#writeUtf8(...)and related methods to operate on a sub-charsequence directly to save having to allocate substrings, but it missed an edge case where the subsequence does not extend to the end of theCharSequenceand the last char in the sequence is a high surrogate.Due to the catch-
IndexOutOfBoundsExceptionoptimization that avoids an additional bounds check, it would be possible to read past the specified end char and successfully decode a surrogate pair that would otherwise result in a'?'byte being written.Modifications
writeUtf8(AbstractByteBuf,int,CharSequence,int,int)andutf8BytesNonAsciimethodsResult
Bug is fixed.
This removes the bounds-check-avoidance optimization but it does not appear to have a measurable impact on benchmark results, including when the char sequence contains many surrogate pairs (which should be rare in any case).