DataInputStream.java

/*
 * Copyright (c) 1994, 2021, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.io;

import java.util.Objects;

/**
 * A data input stream lets an application read primitive Java data
 * types from an underlying input stream in a machine-independent
 * way. An application uses a data output stream to write data that
 * can later be read by a data input stream.
 * <p>
 * A DataInputStream is not safe for use by multiple concurrent
 * threads. If a DataInputStream is to be used by more than one
 * thread then access to the data input stream should be controlled
 * by appropriate synchronization.
 *
 * @author  Arthur van Hoff
 * @see     java.io.DataOutputStream
 * @since   1.0
 */
public class DataInputStream extends FilterInputStream implements DataInput {

    /**
     * Creates a DataInputStream that uses the specified
     * underlying InputStream.
     *
     * @param  in   the specified input stream
     */
    public DataInputStream(InputStream in) {
        super(in);
    }

    /**
     * working arrays initialized on demand by readUTF
     */
    private byte bytearr[] = new byte[80];
    private char chararr[] = new char[80];

    /**
     * Reads some number of bytes from the contained input stream and
     * stores them into the buffer array {@code b}. The number of
     * bytes actually read is returned as an integer. This method blocks
     * until input data is available, end of file is detected, or an
     * exception is thrown.
     *
     * <p>If {@code b} is null, a {@code NullPointerException} is
     * thrown. If the length of {@code b} is zero, then no bytes are
     * read and {@code 0} is returned; otherwise, there is an attempt
     * to read at least one byte. If no byte is available because the
     * stream is at end of file, the value {@code -1} is returned;
     * otherwise, at least one byte is read and stored into {@code b}.
     *
     * <p>The first byte read is stored into element {@code b[0]}, the
     * next one into {@code b[1]}, and so on. The number of bytes read
     * is, at most, equal to the length of {@code b}. Let {@code k}
     * be the number of bytes actually read; these bytes will be stored in
     * elements {@code b[0]} through {@code b[k-1]}, leaving
     * elements {@code b[k]} through {@code b[b.length-1]}
     * unaffected.
     *
     * <p>The {@code read(b)} method has the same effect as:
     * <blockquote><pre>
     * read(b, 0, b.length)
     * </pre></blockquote>
     *
     * @param      b   the buffer into which the data is read.
     * @return     the total number of bytes read into the buffer, or
     *             {@code -1} if there is no more data because the end
     *             of the stream has been reached.
     * @throws     IOException if the first byte cannot be read for any reason
     *             other than end of file, the stream has been closed and the underlying
     *             input stream does not support reading after close, or another I/O
     *             error occurs.
     * @see        java.io.FilterInputStream#in
     * @see        java.io.InputStream#read(byte[], int, int)
     */
    public final int read(byte b[]) throws IOException {
        return in.read(b, 0, b.length);
    }

    /**
     * Reads up to {@code len} bytes of data from the contained
     * input stream into an array of bytes.  An attempt is made to read
     * as many as {@code len} bytes, but a smaller number may be read,
     * possibly zero. The number of bytes actually read is returned as an
     * integer.
     *
     * <p> This method blocks until input data is available, end of file is
     * detected, or an exception is thrown.
     *
     * <p> If {@code len} is zero, then no bytes are read and
     * {@code 0} is returned; otherwise, there is an attempt to read at
     * least one byte. If no byte is available because the stream is at end of
     * file, the value {@code -1} is returned; otherwise, at least one
     * byte is read and stored into {@code b}.
     *
     * <p> The first byte read is stored into element {@code b[off]}, the
     * next one into {@code b[off+1]}, and so on. The number of bytes read
     * is, at most, equal to {@code len}. Let <i>k</i> be the number of
     * bytes actually read; these bytes will be stored in elements
     * {@code b[off]} through {@code b[off+}<i>k</i>{@code -1]},
     * leaving elements {@code b[off+}<i>k</i>{@code ]} through
     * {@code b[off+len-1]} unaffected.
     *
     * <p> In every case, elements {@code b[0]} through
     * {@code b[off]} and elements {@code b[off+len]} through
     * {@code b[b.length-1]} are unaffected.
     *
     * @param      b     the buffer into which the data is read.
     * @param      off the start offset in the destination array {@code b}
     * @param      len   the maximum number of bytes read.
     * @return     the total number of bytes read into the buffer, or
     *             {@code -1} if there is no more data because the end
     *             of the stream has been reached.
     * @throws     NullPointerException If {@code b} is {@code null}.
     * @throws     IndexOutOfBoundsException If {@code off} is negative,
     *             {@code len} is negative, or {@code len} is greater than
     *             {@code b.length - off}
     * @throws     IOException if the first byte cannot be read for any reason
     *             other than end of file, the stream has been closed and the underlying
     *             input stream does not support reading after close, or another I/O
     *             error occurs.
     * @see        java.io.FilterInputStream#in
     * @see        java.io.InputStream#read(byte[], int, int)
     */
    public final int read(byte b[], int off, int len) throws IOException {
        return in.read(b, off, len);
    }

    /**
     * See the general contract of the {@code readFully}
     * method of {@code DataInput}.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @param   b   the buffer into which the data is read.
     * @throws  NullPointerException if {@code b} is {@code null}.
     * @throws  EOFException  if this input stream reaches the end before
     *          reading all the bytes.
     * @throws  IOException   the stream has been closed and the contained
     *          input stream does not support reading after close, or
     *          another I/O error occurs.
     * @see     java.io.FilterInputStream#in
     */
    public final void readFully(byte b[]) throws IOException {
        readFully(b, 0, b.length);
    }

    /**
     * See the general contract of the {@code readFully}
     * method of {@code DataInput}.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @param      b     the buffer into which the data is read.
     * @param      off   the start offset in the data array {@code b}.
     * @param      len   the number of bytes to read.
     * @throws     NullPointerException if {@code b} is {@code null}.
     * @throws     IndexOutOfBoundsException if {@code off} is negative,
     *             {@code len} is negative, or {@code len} is greater than
     *             {@code b.length - off}.
     * @throws     EOFException  if this input stream reaches the end before
     *             reading all the bytes.
     * @throws     IOException   the stream has been closed and the contained
     *             input stream does not support reading after close, or
     *             another I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    public final void readFully(byte b[], int off, int len) throws IOException {
        Objects.checkFromIndexSize(off, len, b.length);
        int n = 0;
        while (n < len) {
            int count = in.read(b, off + n, len - n);
            if (count < 0)
                throw new EOFException();
            n += count;
        }
    }

    /**
     * See the general contract of the {@code skipBytes}
     * method of {@code DataInput}.
     * <p>
     * Bytes for this operation are read from the contained
     * input stream.
     *
     * @param      n   the number of bytes to be skipped.
     * @return     the actual number of bytes skipped.
     * @throws     IOException  if the contained input stream does not support
     *             seek, or the stream has been closed and
     *             the contained input stream does not support
     *             reading after close, or another I/O error occurs.
     */
    public final int skipBytes(int n) throws IOException {
        int total = 0;
        int cur = 0;

        while ((total<n) && ((cur = (int) in.skip(n-total)) > 0)) {
            total += cur;
        }

        return total;
    }

    /**
     * See the general contract of the {@code readBoolean}
     * method of {@code DataInput}.
     * <p>
     * Bytes for this operation are read from the contained
     * input stream.
     *
     * @return     the {@code boolean} value read.
     * @throws     EOFException  if this input stream has reached the end.
     * @throws     IOException   the stream has been closed and the contained
     *             input stream does not support reading after close, or
     *             another I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    public final boolean readBoolean() throws IOException {
        int ch = in.read();
        if (ch < 0)
            throw new EOFException();
        return (ch != 0);
    }

    /**
     * See the general contract of the {@code readByte}
     * method of {@code DataInput}.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next byte of this input stream as a signed 8-bit
     *             {@code byte}.
     * @throws     EOFException  if this input stream has reached the end.
     * @throws     IOException   the stream has been closed and the contained
     *             input stream does not support reading after close, or
     *             another I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    public final byte readByte() throws IOException {
        int ch = in.read();
        if (ch < 0)
            throw new EOFException();
        return (byte)(ch);
    }

    /**
     * See the general contract of the {@code readUnsignedByte}
     * method of {@code DataInput}.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next byte of this input stream, interpreted as an
     *             unsigned 8-bit number.
     * @throws     EOFException  if this input stream has reached the end.
     * @throws     IOException   the stream has been closed and the contained
     *             input stream does not support reading after close, or
     *             another I/O error occurs.
     * @see         java.io.FilterInputStream#in
     */
    public final int readUnsignedByte() throws IOException {
        int ch = in.read();
        if (ch < 0)
            throw new EOFException();
        return ch;
    }

    /**
     * See the general contract of the {@code readShort}
     * method of {@code DataInput}.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next two bytes of this input stream, interpreted as a
     *             signed 16-bit number.
     * @throws     EOFException  if this input stream reaches the end before
     *               reading two bytes.
     * @throws     IOException   the stream has been closed and the contained
     *             input stream does not support reading after close, or
     *             another I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    public final short readShort() throws IOException {
        int ch1 = in.read();
        int ch2 = in.read();
        if ((ch1 | ch2) < 0)
            throw new EOFException();
        return (short)((ch1 << 8) + (ch2 << 0));
    }

    /**
     * See the general contract of the {@code readUnsignedShort}
     * method of {@code DataInput}.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next two bytes of this input stream, interpreted as an
     *             unsigned 16-bit integer.
     * @throws     EOFException  if this input stream reaches the end before
     *             reading two bytes.
     * @throws     IOException   the stream has been closed and the contained
     *             input stream does not support reading after close, or
     *             another I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    public final int readUnsignedShort() throws IOException {
        int ch1 = in.read();
        int ch2 = in.read();
        if ((ch1 | ch2) < 0)
            throw new EOFException();
        return (ch1 << 8) + (ch2 << 0);
    }

    /**
     * See the general contract of the {@code readChar}
     * method of {@code DataInput}.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next two bytes of this input stream, interpreted as a
     *             {@code char}.
     * @throws     EOFException  if this input stream reaches the end before
     *               reading two bytes.
     * @throws     IOException   the stream has been closed and the contained
     *             input stream does not support reading after close, or
     *             another I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    public final char readChar() throws IOException {
        int ch1 = in.read();
        int ch2 = in.read();
        if ((ch1 | ch2) < 0)
            throw new EOFException();
        return (char)((ch1 << 8) + (ch2 << 0));
    }

    /**
     * See the general contract of the {@code readInt}
     * method of {@code DataInput}.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next four bytes of this input stream, interpreted as an
     *             {@code int}.
     * @throws     EOFException  if this input stream reaches the end before
     *               reading four bytes.
     * @throws     IOException   the stream has been closed and the contained
     *             input stream does not support reading after close, or
     *             another I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    public final int readInt() throws IOException {
        int ch1 = in.read();
        int ch2 = in.read();
        int ch3 = in.read();
        int ch4 = in.read();
        if ((ch1 | ch2 | ch3 | ch4) < 0)
            throw new EOFException();
        return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
    }

    private byte readBuffer[] = new byte[8];

    /**
     * See the general contract of the {@code readLong}
     * method of {@code DataInput}.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next eight bytes of this input stream, interpreted as a
     *             {@code long}.
     * @throws     EOFException  if this input stream reaches the end before
     *               reading eight bytes.
     * @throws     IOException   the stream has been closed and the contained
     *             input stream does not support reading after close, or
     *             another I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    public final long readLong() throws IOException {
        readFully(readBuffer, 0, 8);
        return (((long)readBuffer[0] << 56) +
                ((long)(readBuffer[1] & 255) << 48) +
                ((long)(readBuffer[2] & 255) << 40) +
                ((long)(readBuffer[3] & 255) << 32) +
                ((long)(readBuffer[4] & 255) << 24) +
                ((readBuffer[5] & 255) << 16) +
                ((readBuffer[6] & 255) <<  8) +
                ((readBuffer[7] & 255) <<  0));
    }

    /**
     * See the general contract of the {@code readFloat}
     * method of {@code DataInput}.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next four bytes of this input stream, interpreted as a
     *             {@code float}.
     * @throws     EOFException  if this input stream reaches the end before
     *               reading four bytes.
     * @throws     IOException   the stream has been closed and the contained
     *             input stream does not support reading after close, or
     *             another I/O error occurs.
     * @see        java.io.DataInputStream#readInt()
     * @see        java.lang.Float#intBitsToFloat(int)
     */
    public final float readFloat() throws IOException {
        return Float.intBitsToFloat(readInt());
    }

    /**
     * See the general contract of the {@code readDouble}
     * method of {@code DataInput}.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     the next eight bytes of this input stream, interpreted as a
     *             {@code double}.
     * @throws     EOFException  if this input stream reaches the end before
     *               reading eight bytes.
     * @throws     IOException   the stream has been closed and the contained
     *             input stream does not support reading after close, or
     *             another I/O error occurs.
     * @see        java.io.DataInputStream#readLong()
     * @see        java.lang.Double#longBitsToDouble(long)
     */
    public final double readDouble() throws IOException {
        return Double.longBitsToDouble(readLong());
    }

    private char lineBuffer[];

    /**
     * See the general contract of the {@code readLine}
     * method of {@code DataInput}.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @deprecated This method does not properly convert bytes to characters.
     * As of JDK&nbsp;1.1, the preferred way to read lines of text is via the
     * {@code BufferedReader.readLine()} method.  Programs that use the
     * {@code DataInputStream} class to read lines can be converted to use
     * the {@code BufferedReader} class by replacing code of the form:
     * <blockquote><pre>
     *     DataInputStream d =&nbsp;new&nbsp;DataInputStream(in);
     * </pre></blockquote>
     * with:
     * <blockquote><pre>
     *     BufferedReader d
     *          =&nbsp;new&nbsp;BufferedReader(new&nbsp;InputStreamReader(in));
     * </pre></blockquote>
     *
     * @return     the next line of text from this input stream.
     * @throws     IOException  if an I/O error occurs.
     * @see        java.io.BufferedReader#readLine()
     * @see        java.io.FilterInputStream#in
     */
    @Deprecated
    public final String readLine() throws IOException {
        char buf[] = lineBuffer;

        if (buf == null) {
            buf = lineBuffer = new char[128];
        }

        int room = buf.length;
        int offset = 0;
        int c;

loop:   while (true) {
            switch (c = in.read()) {
              case -1:
              case '\n':
                break loop;

              case '\r':
                int c2 = in.read();
                if ((c2 != '\n') && (c2 != -1)) {
                    if (!(in instanceof PushbackInputStream)) {
                        this.in = new PushbackInputStream(in);
                    }
                    ((PushbackInputStream)in).unread(c2);
                }
                break loop;

              default:
                if (--room < 0) {
                    buf = new char[offset + 128];
                    room = buf.length - offset - 1;
                    System.arraycopy(lineBuffer, 0, buf, 0, offset);
                    lineBuffer = buf;
                }
                buf[offset++] = (char) c;
                break;
            }
        }
        if ((c == -1) && (offset == 0)) {
            return null;
        }
        return String.copyValueOf(buf, 0, offset);
    }

    /**
     * See the general contract of the {@code readUTF}
     * method of {@code DataInput}.
     * <p>
     * Bytes
     * for this operation are read from the contained
     * input stream.
     *
     * @return     a Unicode string.
     * @throws     EOFException  if this input stream reaches the end before
     *               reading all the bytes.
     * @throws     IOException   the stream has been closed and the contained
     *             input stream does not support reading after close, or
     *             another I/O error occurs.
     * @throws     UTFDataFormatException if the bytes do not represent a valid
     *             modified UTF-8 encoding of a string.
     * @see        java.io.DataInputStream#readUTF(java.io.DataInput)
     */
    public final String readUTF() throws IOException {
        return readUTF(this);
    }

    /**
     * Reads from the
     * stream {@code in} a representation
     * of a Unicode  character string encoded in
     * <a href="DataInput.html#modified-utf-8">modified UTF-8</a> format;
     * this string of characters is then returned as a {@code String}.
     * The details of the modified UTF-8 representation
     * are  exactly the same as for the {@code readUTF}
     * method of {@code DataInput}.
     *
     * @param      in   a data input stream.
     * @return     a Unicode string.
     * @throws     EOFException            if the input stream reaches the end
     *               before all the bytes.
     * @throws     IOException   the stream has been closed and the contained
     *             input stream does not support reading after close, or
     *             another I/O error occurs.
     * @throws     UTFDataFormatException  if the bytes do not represent a
     *               valid modified UTF-8 encoding of a Unicode string.
     * @see        java.io.DataInputStream#readUnsignedShort()
     */
    public static final String readUTF(DataInput in) throws IOException {
        int utflen = in.readUnsignedShort();
        byte[] bytearr = null;
        char[] chararr = null;
        if (in instanceof DataInputStream dis) {
            if (dis.bytearr.length < utflen){
                dis.bytearr = new byte[utflen*2];
                dis.chararr = new char[utflen*2];
            }
            chararr = dis.chararr;
            bytearr = dis.bytearr;
        } else {
            bytearr = new byte[utflen];
            chararr = new char[utflen];
        }

        int c, char2, char3;
        int count = 0;
        int chararr_count=0;

        in.readFully(bytearr, 0, utflen);

        while (count < utflen) {
            c = (int) bytearr[count] & 0xff;
            if (c > 127) break;
            count++;
            chararr[chararr_count++]=(char)c;
        }

        while (count < utflen) {
            c = (int) bytearr[count] & 0xff;
            switch (c >> 4) {
                case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
                    /* 0xxxxxxx*/
                    count++;
                    chararr[chararr_count++]=(char)c;
                    break;
                case 12: case 13:
                    /* 110x xxxx   10xx xxxx*/
                    count += 2;
                    if (count > utflen)
                        throw new UTFDataFormatException(
                            "malformed input: partial character at end");
                    char2 = (int) bytearr[count-1];
                    if ((char2 & 0xC0) != 0x80)
                        throw new UTFDataFormatException(
                            "malformed input around byte " + count);
                    chararr[chararr_count++]=(char)(((c & 0x1F) << 6) |
                                                    (char2 & 0x3F));
                    break;
                case 14:
                    /* 1110 xxxx  10xx xxxx  10xx xxxx */
                    count += 3;
                    if (count > utflen)
                        throw new UTFDataFormatException(
                            "malformed input: partial character at end");
                    char2 = (int) bytearr[count-2];
                    char3 = (int) bytearr[count-1];
                    if (((char2 & 0xC0) != 0x80) || ((char3 & 0xC0) != 0x80))
                        throw new UTFDataFormatException(
                            "malformed input around byte " + (count-1));
                    chararr[chararr_count++]=(char)(((c     & 0x0F) << 12) |
                                                    ((char2 & 0x3F) << 6)  |
                                                    ((char3 & 0x3F) << 0));
                    break;
                default:
                    /* 10xx xxxx,  1111 xxxx */
                    throw new UTFDataFormatException(
                        "malformed input around byte " + count);
            }
        }
        // The number of chars produced may be less than utflen
        return new String(chararr, 0, chararr_count);
    }
}