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package com.seaofnodes.simple.fuzzer;
import java.util.Arrays;
import java.util.function.BiConsumer;
import java.util.function.Consumer;
import java.util.function.Predicate;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* This class is used to reduce test cases created by the fuzzer.
* It applies rewrite rules to the test case and checks that the
* test still produces the same exception.
* This is done in a fixpoint iteration until every rewrite produces
* no or a different exception.
*/
public class Reducer {
private interface Replacer extends BiConsumer<StringBuilder, Matcher> {}
/**
* Holder for the rewrite rules
*/
private record Replace(Pattern pattern, boolean iterate, Replacer... replacements) {
Replace(Pattern p, Object... replacements) {
this(p, replacements[0] == Boolean.TRUE, Arrays.stream(replacements).filter(o->!(o instanceof Boolean)).map(Replace::from).toArray(Replacer[]::new));
}
private static Replacer from(Object o) {
if (o instanceof Replacer r) return r;
if (o instanceof Integer i) return (s, m)->s.append(m.group(i));
if (o instanceof String r) return (s, m)->s.append(r);
throw new IllegalArgumentException();
}
}
/**
* List of rewrite rules.
*/
private static final Replace[] REPLACEMENTS = {
new Replace(Pattern.compile("\\b(?:[^\\W0]|\\w\\w+)\\b"), "0", "1"),
new Replace(Pattern.compile("(?<=\\n|^)[^\\n]+(?=\\n|$)"), true, ""),
new Replace(Pattern.compile("(?<=[+\\-*/<>=(])--"), ""),
new Replace(Pattern.compile("\\b--"), "+"),
new Replace(Pattern.compile("[-!]"), ""),
new Replace(Pattern.compile("\\b\\+-"), "-"),
new Replace(Pattern.compile("(?<![+\\-*/<>=&|])(?:-|\\*|/|>=|<=|>>>|>>|>|<<|<|!=|==|&&|\\|\\||&|\\||^)(?![+*/<>=&|])"), "+"),
new Replace(Pattern.compile("\\?([^;]+):"), "+"),
new Replace(Pattern.compile("\\{((?:[^{}]|\\{})+)(?:\\n[ \\t]*)?}"), "", "{}", 1),
new Replace(Pattern.compile("(?<=\\n|^)([ \\t]*)\\{\\n(.*?)\\n\\1}", Pattern.DOTALL), 2),
new Replace(Pattern.compile("\\(([^()]+)\\)"), 1),
new Replace(Pattern.compile("\\d+ ?\\+ ?"), ""),
new Replace(Pattern.compile(" ?\\+ ?\\d+"), ""),
new Replace(Pattern.compile("\\n\\n+"), "\n"),
new Replace(Pattern.compile("^\\n+|\\n+$"), ""),
new Replace(Pattern.compile("else *"), ""),
new Replace(Pattern.compile("\\bif\\([^()]+\\) *"), ""),
new Replace(Pattern.compile("\\bwhile\\([^()]+\\) *"), ""),
new Replace(Pattern.compile("\\bstruct \\w+ \\{[^{}]*}"), "")
};
/**
* Predicate to test if the reduced script generates the same error.
*/
private final Predicate<String> tester;
/**
* Create a reducer with a test function.
* @param tester Test function which returns true when the same issue is found in the script.
*/
private Reducer(Predicate<String> tester) {
this.tester = tester;
}
/**
* Rewrites the script with one rewrite rule.
*/
private String doReplacement(String script, Pattern pattern, Replacer[] replacements) {
var matcher = pattern.matcher(script);
var sb = new StringBuilder();
var last = 0;
var skip = 0;
outer:
while (matcher.find(last + skip)) {
sb.append(script, last, matcher.start());
last = matcher.end();
skip = last == matcher.start() ? 1 : 0;
var pos = sb.length();
for (var replacement : replacements) {
replacement.accept(sb, matcher);
var tail = sb.length();
sb.append(script, last, script.length());
if (tester.test(sb.toString())) {
sb.setLength(tail);
continue outer;
}
sb.setLength(pos);
}
last = matcher.start();
skip = 1;
}
sb.append(script, last, script.length());
return sb.toString();
}
/**
* Clean up variable names from the random ones generated by the fuzzer.
*/
private String cleanVariables(String script) {
var matcher = Pattern.compile("\\b([0-9a-zA-Z_]+) !?([0-9a-zA-Z_]+)").matcher(script);
int[] num = {0, 0};
while (matcher.find()) {
var type = matcher.group(1);
var var = matcher.group(2);
if (type.equals("new")) continue;
String prefix = "v";
int t = 0;
if (type.equals("struct")) {
t = 1;
prefix = "s";
}
if (var.matches(prefix+"\\d+")) continue;
while (script.contains(prefix+num[t])) num[t]++;
var n = script.replaceAll("\\b"+var+"\\b", prefix + num[t]);
if (tester.test(n)) {
script = n;
}
}
return script;
}
/**
* Run all rewrite rules once.
*/
private String doAllReplacements(String script) {
for (var replace: REPLACEMENTS) {
String old;
do {
old = script;
script = doReplacement(script, replace.pattern, replace.replacements);
} while (replace.iterate && !old.equals(script));
}
return script;
}
/**
* Reduce the script to a minimal version which produces the same problem with a test function.
* @param tester Test function which returns true when the same issue is found in the script.
*/
public static String reduce(String script, Predicate<String> tester) {
var reducer = new Reducer(tester);
String old;
do {
old = script;
script = reducer.doAllReplacements(script);
script = reducer.cleanVariables(script);
} while (!script.equals(old));
return script;
}
/**
* Reduce the script to a minimal version which produces the same problem with a reproducer.
* @param ex The exception originally caused by the script
* @param reproducer Test function which throws an exception which will be checked against ex.
*/
public static String reduce(String script, Throwable ex, Consumer<String> reproducer) {
return reduce(script, s->{
Throwable nex = null;
try {
reproducer.accept(s);
} catch (Throwable e) {
nex = e;
}
return FuzzerUtils.isExceptionFromSameCause(nex, ex);
});
}
}
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