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/*
* =========================================================================================
* Copyright 2013-2014 the kamon project <http://kamon.io/>
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the
* License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
* either express or implied. See the License for the specific language governing permissions
* and limitations under the License.
* =========================================================================================
*/
package kamon.util;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* Default implementation of PathFilter. Uses glob based includes and excludes to determine whether to export.
*
* @author John E. Bailey
* @author <a href="mailto:david.lloyd@redhat.com">David M. Lloyd</a>
*/
public final class GlobPathFilter implements PathFilter {
private static final Pattern GLOB_PATTERN = Pattern.compile("(\\*\\*?)|(\\?)|(\\\\.)|(/+)|([^*?]+)");
private final String glob;
private final Pattern pattern;
/**
* Construct a new instance.
*
* @param glob the path glob to match
*/
public GlobPathFilter(final String glob) {
pattern = getGlobPattern(glob);
this.glob = glob;
}
/**
* Determine whether a path should be accepted.
*
* @param path the path to check
* @return true if the path should be accepted, false if not
*/
public boolean accept(final String path) {
return pattern.matcher(path).matches();
}
/**
* Get a regular expression pattern which accept any path names which match the given glob. The glob patterns
* function similarly to {@code ant} file patterns. Valid metacharacters in the glob pattern include:
* <ul>
* <li><code>"\"</code> - escape the next character (treat it literally, even if it is itself a recognized metacharacter)</li>
* <li><code>"?"</code> - match any non-slash character</li>
* <li><code>"*"</code> - match zero or more non-slash characters</li>
* <li><code>"**"</code> - match zero or more characters, including slashes</li>
* <li><code>"/"</code> - match one or more slash characters. Consecutive {@code /} characters are collapsed down into one.</li>
* </ul>
* In addition, any glob pattern matches all subdirectories thereof. A glob pattern ending in {@code /} is equivalent
* to a glob pattern ending in <code>/**</code> in that the named directory is not itself included in the glob.
* <p/>
* <b>See also:</b> <a href="http://ant.apache.org/manual/dirtasks.html#patterns">"Patterns" in the Ant Manual</a>
*
* @param glob the glob to match
*
* @return the pattern
*/
private static Pattern getGlobPattern(final String glob) {
StringBuilder patternBuilder = new StringBuilder();
final Matcher m = GLOB_PATTERN.matcher(glob);
boolean lastWasSlash = false;
while (m.find()) {
lastWasSlash = false;
String grp;
if ((grp = m.group(1)) != null) {
// match a * or **
if (grp.length() == 2) {
// it's a *workers are able to process multiple metrics*
patternBuilder.append(".*");
} else {
// it's a *
patternBuilder.append("[^/]*");
}
} else if ((grp = m.group(2)) != null) {
// match a '?' glob pattern; any non-slash character
patternBuilder.append("[^/]");
} else if ((grp = m.group(3)) != null) {
// backslash-escaped value
patternBuilder.append(Pattern.quote(m.group().substring(1)));
} else if ((grp = m.group(4)) != null) {
// match any number of / chars
patternBuilder.append("/+");
lastWasSlash = true;
} else {
// some other string
patternBuilder.append(Pattern.quote(m.group()));
}
}
if (lastWasSlash) {
// ends in /, append **
patternBuilder.append(".*");
}
return Pattern.compile(patternBuilder.toString());
}
}
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