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The UnboundID LDAP SDK for Java is a fast, comprehensive, and easy-to-use Java API for communicating with LDAP directory servers and performing related tasks like reading and writing LDIF, encoding and decoding data using base64 and ASN.1 BER, and performing secure communication. This package contains the Standard Edition of the LDAP SDK, which is a complete, general-purpose library for communicating with LDAPv3 directory servers.
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/*
 * Copyright 2018-2024 Ping Identity Corporation
 * All Rights Reserved.
 */
/*
 * Copyright 2018-2024 Ping Identity Corporation
 *
 * 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.
 */
/*
 * Copyright (C) 2018-2024 Ping Identity Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License (GPLv2 only)
 * or the terms of the GNU Lesser General Public License (LGPLv2.1 only)
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see .
 */
package com.unboundid.util;



import java.io.File;
import java.io.IOException;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;

import com.unboundid.ldap.sdk.LDAPException;
import com.unboundid.ldap.sdk.LDAPRuntimeException;
import com.unboundid.ldap.sdk.ResultCode;

import static com.unboundid.util.UtilityMessages.*;



/**
 * This class defines a stream file value pattern component, which may be used
 * to provide string values read from a specified local file.  Values will only
 * be accessed in sequential order, and only a relatively small amount of data
 * will be held in memory at any given time, so this may be a suitable option
 * for dealing with very large files.
 */
final class StreamFileValuePatternComponent
      extends ValuePatternComponent
{
  /**
   * The serial version UID for this serializable class.
   */
  private static final long serialVersionUID = -4557045230341165225L;



  // A value that tracks the position at which the next line of data should be
  // read from the file.
  @NotNull private final AtomicLong nextReadPosition;

  // A reference that holds this thread and makes it available to the associated
  // StreamFileValuePatternComponent.
  @NotNull private final AtomicReference
       threadRef;

  // The file from which the data will be read.
  @NotNull private final File file;

  // The queue that will be used to hold the lines of data read from the file.
  @NotNull private final LinkedBlockingQueue lineQueue;

  // The maximum length of time in milliseconds that an attempt to offer a
  // string to the queue will be allowed to block before the associated reader
  // thread will exit.
  private final long maxOfferBlockTimeMillis;



  /**
   * Creates a new stream file value pattern component that will read data from
   * the specified file.  It will use a queue size of 1000 strings and a maximum
   * block time of 60,000 milliseconds (1 minute).
   *
   * @param  path  The path to the file from which data is to be read.
   *
   * @throws  IOException  If a problem is encountered while trying to open the
   *                       specified file for reading.
   */
  StreamFileValuePatternComponent(@NotNull final String path)
       throws IOException
  {
    this(path, 10_000, 60_000L);
  }



  /**
   * Creates a new stream file value pattern component that will read data from
   * the specified file.
   *
   * @param  path                     The path to the file from which data is to
   *                                  be read.  It must not be {@code null}, and
   *                                  it must reference a file that exists.
   * @param  queueSize                The maximum number of lines read from the
   *                                  file that should be held in memory at any
   *                                  given time.  It must be greater than zero.
   * @param  maxOfferBlockTimeMillis  The maximum length of time in milliseconds
   *                                  that an attempt to offer a string into the
   *                                  queue will be allowed to block before the
   *                                  associated reader thread will exit.  It
   *                                  must be greater than zero.
   *
   * @throws  IOException  If a problem is encountered while trying to open the
   *                       specified file for reading.
   */
  StreamFileValuePatternComponent(@NotNull final String path,
                                  final int queueSize,
                                  final long maxOfferBlockTimeMillis)
       throws IOException
  {
    Validator.ensureNotNull(path);
    Validator.ensureTrue(queueSize > 0);
    Validator.ensureTrue(maxOfferBlockTimeMillis > 0L);

    this.maxOfferBlockTimeMillis = maxOfferBlockTimeMillis;

    file = new File(path);
    if (! file.exists())
    {
      throw new IOException(ERR_STREAM_FILE_VALUE_PATTERN_PATH_MISSING.get(
           file.getAbsolutePath()));
    }

    if (! file.isFile())
    {
      throw new IOException(ERR_STREAM_FILE_VALUE_PATTERN_PATH_NOT_FILE.get(
           file.getAbsolutePath()));
    }

    if (file.length() <= 0)
    {
      throw new IOException(ERR_STREAM_FILE_VALUE_PATTERN_FILE_EMPTY.get(
           file.getAbsolutePath()));
    }

    lineQueue = new LinkedBlockingQueue<>(queueSize);
    nextReadPosition = new AtomicLong(0L);
    threadRef = new AtomicReference<>();

    final StreamFileValuePatternReaderThread readerThread =
         new StreamFileValuePatternReaderThread(file, lineQueue,
              maxOfferBlockTimeMillis, nextReadPosition, threadRef);
    threadRef.set(readerThread);
    readerThread.start();
  }



  /**
   * {@inheritDoc}
   */
  @Override()
  void append(@NotNull final StringBuilder buffer)
  {
    String line = lineQueue.poll();
    if (line != null)
    {
      buffer.append(line);
      return;
    }

    while (true)
    {
      try
      {
        StreamFileValuePatternReaderThread readerThread;
        synchronized (this)
        {
          readerThread = threadRef.get();
          if (readerThread == null)
          {
            readerThread = new StreamFileValuePatternReaderThread(file,
                 lineQueue, maxOfferBlockTimeMillis, nextReadPosition,
                 threadRef);
            threadRef.set(readerThread);
            readerThread.start();
          }
        }

        line = lineQueue.poll(10L, TimeUnit.MILLISECONDS);
        if (line != null)
        {
          buffer.append(line);
          return;
        }
      }
      catch (final Exception e)
      {
        Debug.debugException(e);
        throw new LDAPRuntimeException(
             new LDAPException(ResultCode.LOCAL_ERROR,
                  ERR_STREAM_FILE_VALUE_PATTERN_ERROR_GETTING_NEXT_VALUE.get(
                       file.getAbsolutePath(),
                       StaticUtils.getExceptionMessage(e)),
                  e));
      }
    }
  }



  /**
   * {@inheritDoc}
   */
  @Override()
  boolean supportsBackReference()
  {
    return true;
  }
}