PushReader.java

/*
 * Copyright 2000-2016 JetBrains s.r.o.
 *
 * 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 com.intellij.lang.ant.segments;

import gnu.trove.TIntArrayList;
import org.jetbrains.annotations.NonNls;

import java.io.IOException;
import java.io.Reader;

/**
 * @author dyoma
 */
public class PushReader {
  private final Reader mySource;
  private final TIntArrayList myReadAhead = new TIntArrayList();
  @NonNls
  protected static final String INTERNAL_ERROR_UNEXPECTED_END_OF_PIPE = "Unexpected end of pipe";

  public PushReader(final Reader source) {
    mySource = source;
  }

  public int next() throws IOException {
    return myReadAhead.isEmpty() ? mySource.read() : myReadAhead.remove(myReadAhead.size() - 1);
  }

  public void pushBack(final char[] chars) {
    for (int i = chars.length - 1; i >= 0; i--) {
      final char aChar = chars[i];
      myReadAhead.add(aChar);
    }
  }

  public void close() throws IOException {
    mySource.close();
  }

  public boolean ready() throws IOException {
    return !myReadAhead.isEmpty() || mySource.ready();
  }

  public void pushBack(final int aChar) {
    myReadAhead.add(aChar);
  }

  public char[] next(final int charCount) throws IOException {
    final char[] chars = new char[charCount];
    int offset = 0;
    for (; offset < chars.length && offset < myReadAhead.size(); offset++)
      chars[offset] = (char)myReadAhead.remove(myReadAhead.size() - 1);

    while (offset < chars.length) {
      int bytesRead = mySource.read(chars, offset, chars.length - offset);
      if (bytesRead == -1)
        throw new IOException (INTERNAL_ERROR_UNEXPECTED_END_OF_PIPE);
      offset += bytesRead;
    }

    return chars;
  }
}