hdfs.jsr203.HadoopUtils Maven / Gradle / Ivy

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/*
 * Copyright 2016 Damien Carol 
 *
 * 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 hdfs.jsr203;

import java.util.Arrays;
import java.util.regex.PatternSyntaxException;

class HadoopUtils {
    
    /* Keep private the constructor for this utility class */
    private HadoopUtils() {
    }

	/**
     * Append a slash at the end, if it does not have one yet
     */
    static byte[] toDirectoryPath(byte[] dir) {
        if (dir.length != 0 && dir[dir.length - 1] != '/') {
            dir = Arrays.copyOf(dir, dir.length + 1);
            dir[dir.length - 1] = '/';
        }
        return dir;
    }
    
    private static final String regexMetaChars = ".^$+{[]|()";
    private static final String globMetaChars = "\\*?[{";
    private static boolean isRegexMeta(char c) {
        return regexMetaChars.indexOf(c) != -1;
    }
    private static boolean isGlobMeta(char c) {
        return globMetaChars.indexOf(c) != -1;
    }
    private static char EOL = 0;  //TBD
    private static char next(String glob, int i) {
        if (i < glob.length()) {
            return glob.charAt(i);
        }
        return EOL;
    }
    
    /**
     * Creates a {@code regex} pattern from the given {@code glob} expression.
     *
     * @throws  PatternSyntaxException
     */
    static String toRegexPattern(String globPattern) {
        boolean inGroup = false;
        StringBuilder regex = new StringBuilder("^");

        int i = 0;
        while (i < globPattern.length()) {
            char c = globPattern.charAt(i++);
            switch (c) {
                case '\\':
                    // escape special characters
                    if (i == globPattern.length()) {
                        throw new PatternSyntaxException("No character to escape",
                                globPattern, i - 1);
                    }
                    char next = globPattern.charAt(i++);
                    if (isGlobMeta(next) || isRegexMeta(next)) {
                        regex.append('\\');
                    }
                    regex.append(next);
                    break;
                case '/':
                    regex.append(c);
                    break;
                case '[':
                    // don't match name separator in class
                    regex.append("[[^/]&&[");
                    if (next(globPattern, i) == '^') {
                        // escape the regex negation char if it appears
                        regex.append("\\^");
                        i++;
                    } else {
                        // negation
                        if (next(globPattern, i) == '!') {
                            regex.append('^');
                            i++;
                        }
                        // hyphen allowed at start
                        if (next(globPattern, i) == '-') {
                            regex.append('-');
                            i++;
                        }
                    }
                    boolean hasRangeStart = false;
                    char last = 0;
                    while (i < globPattern.length()) {
                        c = globPattern.charAt(i++);
                        if (c == ']') {
                            break;
                        }
                        if (c == '/') {
                            throw new PatternSyntaxException("Explicit 'name separator' in class",
                                    globPattern, i - 1);
                        }
                        // TBD: how to specify ']' in a class?
                        if (c == '\\' || c == '[' ||
                                c == '&' && next(globPattern, i) == '&') {
                            // escape '\', '[' or "&&" for regex class
                            regex.append('\\');
                        }
                        regex.append(c);

                        if (c == '-') {
                            if (!hasRangeStart) {
                                throw new PatternSyntaxException("Invalid range",
                                        globPattern, i - 1);
                            }
                            if ((c = next(globPattern, i++)) == EOL || c == ']') {
                                break;
                            }
                            if (c < last) {
                                throw new PatternSyntaxException("Invalid range",
                                        globPattern, i - 3);
                            }
                            regex.append(c);
                            hasRangeStart = false;
                        } else {
                            hasRangeStart = true;
                            last = c;
                        }
                    }
                    if (c != ']') {
                        throw new PatternSyntaxException("Missing ']", globPattern, i - 1);
                    }
                    regex.append("]]");
                    break;
                case '{':
                    if (inGroup) {
                        throw new PatternSyntaxException("Cannot nest groups",
                                globPattern, i - 1);
                    }
                    regex.append("(?:(?:");
                    inGroup = true;
                    break;
                case '}':
                    if (inGroup) {
                        regex.append("))");
                        inGroup = false;
                    } else {
                        regex.append('}');
                    }
                    break;
                case ',':
                    if (inGroup) {
                        regex.append(")|(?:");
                    } else {
                        regex.append(',');
                    }
                    break;
                case '*':
                    if (next(globPattern, i) == '*') {
                        // crosses directory boundaries
                        regex.append(".*");
                        i++;
                    } else {
                        // within directory boundary
                        regex.append("[^/]*");
                    }
                    break;
                case '?':
                   regex.append("[^/]");
                   break;
                default:
                    if (isRegexMeta(c)) {
                        regex.append('\\');
                    }
                    regex.append(c);
            }
        }
        if (inGroup) {
            throw new PatternSyntaxException("Missing '}", globPattern, i - 1);
        }
        return regex.append('$').toString();
    }
}