/*
 * 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.tomcat.util.http.fileupload;

import java.io.Closeable;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * General IO stream manipulation utilities.
 * <p>
 * This class provides static utility methods for input/output operations.
 * <ul>
 * <li>closeQuietly - these methods close a stream ignoring nulls and exceptions
 * <li>toXxx/read - these methods read data from a stream
 * <li>write - these methods write data to a stream
 * <li>copy - these methods copy all the data from one stream to another
 * <li>contentEquals - these methods compare the content of two streams
 * </ul>
 * <p>
 * The byte-to-char methods and char-to-byte methods involve a conversion step.
 * Two methods are provided in each case, one that uses the platform default
 * encoding and the other which allows you to specify an encoding. You are
 * encouraged to always specify an encoding because relying on the platform
 * default can lead to unexpected results, for example when moving from
 * development to production.
 * <p>
 * All the methods in this class that read a stream are buffered internally.
 * This means that there is no cause to use a <code>BufferedInputStream</code>
 * or <code>BufferedReader</code>. The default buffer size of 4K has been shown
 * to be efficient in tests.
 * <p>
 * Wherever possible, the methods in this class do <em>not</em> flush or close
 * the stream. This is to avoid making non-portable assumptions about the
 * streams' origin and further use. Thus the caller is still responsible for
 * closing streams after use.
 * <p>
 * Origin of code: Excalibur.
 */
public class IOUtils {
    // NOTE: This class is focussed on InputStream, OutputStream, Reader and
    // Writer. Each method should take at least one of these as a parameter,
    // or return one of them.

    private static final int EOF = -1;

    /**
     * The default buffer size ({@value}) to use for
     * {@link #copyLarge(InputStream, OutputStream)}
     * and
     * {@link #copyLarge(Reader, Writer)}
     */
    private static final int DEFAULT_BUFFER_SIZE = 1024 * 4;

    /**
     * Instances should NOT be constructed in standard programming.
     */
    public IOUtils() {
        super();
    }

    /**
     * Closes a <code>Closeable</code> unconditionally.
     * <p>
     * Equivalent to {@link Closeable#close()}, except any exceptions will be ignored. This is typically used in
     * finally blocks.
     * <p>
     * Example code:
     *
     * <pre>
     * Closeable closeable = null;
     * try {
     *     closeable = new FileReader(&quot;foo.txt&quot;);
     *     // process closeable
     *     closeable.close();
     * } catch (Exception e) {
     *     // error handling
     * } finally {
     *     IOUtils.closeQuietly(closeable);
     * }
     * </pre>
     *
     * Closing all streams:
     *
     * <pre>
     * try {
     *     return IOUtils.copy(inputStream, outputStream);
     * } finally {
     *     IOUtils.closeQuietly(inputStream);
     *     IOUtils.closeQuietly(outputStream);
     * }
     * </pre>
     *
     * @param closeable
     *            the objects to close, may be null or already closed
     * @since 2.0
     */
    public static void closeQuietly(final Closeable closeable) {
        try {
            if (closeable != null) {
                closeable.close();
            }
        } catch (final IOException ioe) {
            // ignore
        }
    }

    // copy from InputStream
    //-----------------------------------------------------------------------
    /**
     * Copy bytes from an <code>InputStream</code> to an
     * <code>OutputStream</code>.
     * <p>
     * This method buffers the input internally, so there is no need to use a
     * <code>BufferedInputStream</code>.
     * <p>
     * Large streams (over 2GB) will return a bytes copied value of
     * <code>-1</code> after the copy has completed since the correct
     * number of bytes cannot be returned as an int. For large streams
     * use the <code>copyLarge(InputStream, OutputStream)</code> method.
     *
     * @param input  the <code>InputStream</code> to read from
     * @param output  the <code>OutputStream</code> to write to
     * @return the number of bytes copied, or -1 if &gt; Integer.MAX_VALUE
     * @throws NullPointerException if the input or output is null
     * @throws IOException if an I/O error occurs
     * @since 1.1
     */
    public static int copy(InputStream input, OutputStream output) throws IOException {
        long count = copyLarge(input, output);
        if (count > Integer.MAX_VALUE) {
            return -1;
        }
        return (int) count;
    }

    /**
     * Copy bytes from a large (over 2GB) <code>InputStream</code> to an
     * <code>OutputStream</code>.
     * <p>
     * This method buffers the input internally, so there is no need to use a
     * <code>BufferedInputStream</code>.
     * <p>
     * The buffer size is given by {@link #DEFAULT_BUFFER_SIZE}.
     *
     * @param input  the <code>InputStream</code> to read from
     * @param output  the <code>OutputStream</code> to write to
     * @return the number of bytes copied
     * @throws NullPointerException if the input or output is null
     * @throws IOException if an I/O error occurs
     * @since 1.3
     */
    public static long copyLarge(InputStream input, OutputStream output)
            throws IOException {

        byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
        long count = 0;
        int n = 0;
        while (EOF != (n = input.read(buffer))) {
            output.write(buffer, 0, n);
            count += n;
        }
        return count;
    }

    /**
     * Reads bytes from an input stream.
     * This implementation guarantees that it will read as many bytes
     * as possible before giving up; this may not always be the case for
     * subclasses of {@link InputStream}.
     *
     * @param input where to read input from
     * @param buffer destination
     * @param offset initial offset into buffer
     * @param length length to read, must be &gt;= 0
     * @return actual length read; may be less than requested if EOF was reached
     * @throws IOException if a read error occurs
     * @since 2.2
     */
    public static int read(final InputStream input, final byte[] buffer, final int offset, final int length) throws IOException {
        if (length < 0) {
            throw new IllegalArgumentException("Length must not be negative: " + length);
        }
        int remaining = length;
        while (remaining > 0) {
            final int location = length - remaining;
            final int count = input.read(buffer, offset + location, remaining);
            if (EOF == count) { // EOF
                break;
            }
            remaining -= count;
        }
        return length - remaining;
    }

    /**
     * Reads the requested number of bytes or fail if there are not enough left.
     * <p>
     * This allows for the possibility that {@link InputStream#read(byte[], int, int)} may
     * not read as many bytes as requested (most likely because of reaching EOF).
     *
     * @param input where to read input from
     * @param buffer destination
     * @param offset initial offset into buffer
     * @param length length to read, must be &gt;= 0
     *
     * @throws IOException if there is a problem reading the file
     * @throws IllegalArgumentException if length is negative
     * @throws EOFException if the number of bytes read was incorrect
     * @since 2.2
     */
    public static void readFully(final InputStream input, final byte[] buffer, final int offset, final int length) throws IOException {
        final int actual = read(input, buffer, offset, length);
        if (actual != length) {
            throw new EOFException("Length to read: " + length + " actual: " + actual);
        }
    }

    /**
     * Reads the requested number of bytes or fail if there are not enough left.
     * <p>
     * This allows for the possibility that {@link InputStream#read(byte[], int, int)} may
     * not read as many bytes as requested (most likely because of reaching EOF).
     *
     * @param input where to read input from
     * @param buffer destination
     *
     * @throws IOException if there is a problem reading the file
     * @throws IllegalArgumentException if length is negative
     * @throws EOFException if the number of bytes read was incorrect
     * @since 2.2
     */
    public static void readFully(final InputStream input, final byte[] buffer) throws IOException {
        readFully(input, buffer, 0, buffer.length);
    }
}