org.apache.hadoop.fs.GlobPattern.java Source code

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Here is the source code for org.apache.hadoop.fs.GlobPattern.java

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/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.hadoop.fs;

import com.google.re2j.Pattern;
import com.google.re2j.PatternSyntaxException;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;

/**
 * A class for POSIX glob pattern with brace expansions.
 */
@InterfaceAudience.Private
@InterfaceStability.Evolving
public class GlobPattern {
    private static final char BACKSLASH = '\\';
    private Pattern compiled;
    private boolean hasWildcard = false;

    /**
     * Construct the glob pattern object with a glob pattern string
     * @param globPattern the glob pattern string
     */
    public GlobPattern(String globPattern) {
        set(globPattern);
    }

    /**
     * @return the compiled pattern
     */
    public Pattern compiled() {
        return compiled;
    }

    /**
     * Compile glob pattern string
     * @param globPattern the glob pattern
     * @return the pattern object
     */
    public static Pattern compile(String globPattern) {
        return new GlobPattern(globPattern).compiled();
    }

    /**
     * Match input against the compiled glob pattern
     * @param s input chars
     * @return true for successful matches
     */
    public boolean matches(CharSequence s) {
        return compiled.matcher(s).matches();
    }

    /**
     * Set and compile a glob pattern
     * @param glob  the glob pattern string
     */
    public void set(String glob) {
        StringBuilder regex = new StringBuilder();
        int setOpen = 0;
        int curlyOpen = 0;
        int len = glob.length();
        hasWildcard = false;

        for (int i = 0; i < len; i++) {
            char c = glob.charAt(i);

            switch (c) {
            case BACKSLASH:
                if (++i >= len) {
                    error("Missing escaped character", glob, i);
                }
                regex.append(c).append(glob.charAt(i));
                continue;
            case '.':
            case '$':
            case '(':
            case ')':
            case '|':
            case '+':
                // escape regex special chars that are not glob special chars
                regex.append(BACKSLASH);
                break;
            case '*':
                regex.append('.');
                hasWildcard = true;
                break;
            case '?':
                regex.append('.');
                hasWildcard = true;
                continue;
            case '{': // start of a group
                regex.append("(?:"); // non-capturing
                curlyOpen++;
                hasWildcard = true;
                continue;
            case ',':
                regex.append(curlyOpen > 0 ? '|' : c);
                continue;
            case '}':
                if (curlyOpen > 0) {
                    // end of a group
                    curlyOpen--;
                    regex.append(")");
                    continue;
                }
                break;
            case '[':
                if (setOpen > 0) {
                    error("Unclosed character class", glob, i);
                }
                setOpen++;
                hasWildcard = true;
                break;
            case '^': // ^ inside [...] can be unescaped
                if (setOpen == 0) {
                    regex.append(BACKSLASH);
                }
                break;
            case '!': // [! needs to be translated to [^
                regex.append(setOpen > 0 && '[' == glob.charAt(i - 1) ? '^' : '!');
                continue;
            case ']':
                // Many set errors like [][] could not be easily detected here,
                // as []], []-] and [-] are all valid POSIX glob and java regex.
                // We'll just let the regex compiler do the real work.
                setOpen = 0;
                break;
            default:
            }
            regex.append(c);
        }

        if (setOpen > 0) {
            error("Unclosed character class", glob, len);
        }
        if (curlyOpen > 0) {
            error("Unclosed group", glob, len);
        }
        compiled = Pattern.compile(regex.toString(), Pattern.DOTALL);
    }

    /**
     * @return true if this is a wildcard pattern (with special chars)
     */
    public boolean hasWildcard() {
        return hasWildcard;
    }

    private static void error(String message, String pattern, int pos) {
        String fullMessage = String.format("%s at pos %d", message, pos);
        throw new PatternSyntaxException(fullMessage, pattern);
    }
}