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fix quadratic time when removing doctype declarations

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Athou
2026-11-03 16:37:01 +01:00
parent 69cf674a02
commit ae707a2602
2 changed files with 55 additions and 2 deletions
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21
commafeed-server/src/main/java/com/commafeed/backend/feed/parser/XMLCleaner.java
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@@ -8,12 +8,13 @@ import org.apache.commons.lang3.StringUtils;
import org.jdom2.Verifier;
import java.util.Collection;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
@Singleton
public class XMLCleaner {
private static final Pattern DOCTYPE_PATTERN = Pattern.compile("<!DOCTYPE[^>]*>", Pattern.CASE_INSENSITIVE);
private static final Pattern DOCTYPE_START_PATTERN = Pattern.compile("<!DOCTYPE", Pattern.CASE_INSENSITIVE);
private final Trie trie = Trie.builder().ignoreOverlaps().addKeywords(HtmlEntities.HTML_ENTITIES).build();
@@ -76,6 +77,22 @@ public class XMLCleaner {
return null;
}
return DOCTYPE_PATTERN.matcher(xml).replaceAll("");
// Equivalent to removing all matches of "<!DOCTYPE[^>]*>", without the quadratic cost of that regex when the
// input contains many "<!DOCTYPE" and no closing bracket after them.
Matcher matcher = DOCTYPE_START_PATTERN.matcher(xml);
StringBuilder sb = new StringBuilder(xml.length());
int pos = 0;
while (matcher.find(pos)) {
int end = xml.indexOf('>', matcher.end());
if (end < 0) {
break;
}
sb.append(xml, pos, matcher.start());
pos = end + 1;
}
return sb.append(xml, pos, xml.length()).toString();
}
}