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ProGuardCORE is a free library to read, analyze, modify, and write Java class files.

There is a newer version: 9.1.6

/*
 * ProGuardCORE -- library to process Java bytecode.
 *
 * Copyright (c) 2002-2021 Guardsquare NV
 *
 * 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 proguard.util;

/**
 * This {@link StringMatcher} tests whether strings start with a given fixed string and then match
 * another optional given {@link StringMatcher}.
 *
 * @author Eric Lafortune
 */
public class FixedStringMatcher extends StringMatcher {
  private final String fixedString;
  private final StringMatcher nextMatcher;

  /**
   * Creates a new FixedStringMatcher.
   *
   * @param fixedString the string to match.
   */
  public FixedStringMatcher(String fixedString) {
    this(fixedString, null);
  }

  /**
   * Creates a new FixedStringMatcher.
   *
   * @param fixedString the string prefix to match.
   * @param nextMatcher an optional string matcher to match the remainder of the string.
   */
  public FixedStringMatcher(String fixedString, StringMatcher nextMatcher) {
    this.fixedString = fixedString;
    this.nextMatcher = nextMatcher;
  }

  // Implementations for StringMatcher.

  @Override
  public String prefix() {
    // Append the next matcher's prefix if applicable
    return (nextMatcher != null && nextMatcher.prefix() != null)
        ? fixedString + nextMatcher.prefix()
        : fixedString;
  }

  @Override
  protected boolean matches(String string, int beginOffset, int endOffset) {
    int stringLength = endOffset - beginOffset;
    int fixedStringLength = fixedString.length();
    return stringLength >= fixedStringLength
        && string.startsWith(fixedString, beginOffset)
        && ((nextMatcher == null && stringLength == fixedStringLength)
            || (nextMatcher != null
                && nextMatcher.matches(string, beginOffset + fixedStringLength, endOffset)));
  }
}