sparklemotion/nokogiri

JRuby: UtfHelpper.writeCharToUtf8 cannot handle unicode supplementary character

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#2410 opened on Jan 5, 2022

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 (9 comments) (0 reactions) (0 assignees)Ruby (5,615 stars) (806 forks)batch import
blockedhelp wantedplatform/jrubytopic/encoding

Description

https://github.com/sparklemotion/nokogiri/blob/55029bfba481338825c99e78af2b182b1cc49e04/ext/java/nokogiri/internals/c14n/UtfHelpper.java#L51

since the Canonicalizer process input String character by character. Java uses 16 bits to represent a character; when the input string contains Unicode characters whose code pen are larger than 0Xffff（65535) it will be split into two char, since neither char will not be
recognized, the Unicode characters will be transferred to 2 ??(3f) instead.

for example, if I want to canonicalize an input that contains 𡏅 via c14n, in the output, 𡏅 will be replaced with ??

Contributor guide

Tech stack
java
Domain
backend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Understanding of Unicode and Java char encoding
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
The issue is in UtfHelpper.java, specifically the method writeCharToUtf8 that processes characters individually, failing for supplementary characters (code points > U+FFFF). The fix should handle surrogate pairs, iterating over the string using codePointAt or similar. Refer to the file line 51 in the linked source.