martin-g commented on a change in pull request #352:
URL: https://github.com/apache/tomcat/pull/352#discussion_r486993681
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File path: java/org/apache/catalina/webresources/JarContents.java
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@@ -0,0 +1,122 @@
+package org.apache.catalina.webresources;
+
+import java.util.BitSet;
+import java.util.Enumeration;
+import java.util.jar.JarEntry;
+import java.util.jar.JarFile;
+
+/**
+ * This class represents the contents of a jar by determining whether a given
+ * resource <b>might</b> be in the cache, based on a bloom filter. This is not
a
+ * general-purpose bloom filter because it contains logic to strip out
+ * characters from the beginning of the key.
+ *
+ * The hash methods are simple but good enough for this purpose.
+ */
+public final class JarContents {
+ private final BitSet bits1;
+ private final BitSet bits2;
+ /**
+ * Constant used by a typical hashing method.
+ */
+ private static final int HASH_PRIME_1 = 31;
+
+ /**
+ * Constant used by a typical hashing method.
+ */
+ private static final int HASH_PRIME_2 = 17;
+
+ /**
+ * Size of the fixed-length bit table. Larger reduces false positives,
+ * smaller saves memory.
+ */
+ private static final int TABLE_SIZE = 2048;
+
+ /**
+ * Parses the passed-in jar and populates the bit array.
+ *
+ * @param jar
+ */
+ public JarContents(JarFile jar) {
+ Enumeration<JarEntry> entries = jar.entries();
+ bits1 = new BitSet(TABLE_SIZE);
+ bits2 = new BitSet(TABLE_SIZE);
+
+ // Enumerations. When will they update this API?!
+ while (entries.hasMoreElements()) {
+ JarEntry entry = entries.nextElement();
+ String name = entry.getName();
+ int startPos = 0;
+
+ // If the path starts with a slash, that's not useful information.
+ // Skipping it increases the significance of our key by
+ // removing an insignificant character.
+ boolean precedingSlash = name.charAt(0) == '/';
+ if (precedingSlash) {
+ startPos = 1;
+ }
+
+ // Find the correct table slot
+ int pathHash1 = hashcode(name, startPos,HASH_PRIME_1);
Review comment:
missing space before the third argument
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