org.jruby/jruby-core/9.2.14.0 : org/jruby/embed/io/ReaderInputStream.java

ReaderInputStream
https://github.com/jruby/jruby/jruby-core: JRuby is the effort to recreate the Ruby (https://www.ruby-lang.org) interpreter in Java. (JRuby)
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 **** BEGIN LICENSE BLOCK *****
Version: EPL 2.0/GPL 2.0/LGPL 2.1
The contents of this file are subject to the Eclipse Public
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except in compliance with the License. You may obtain a copy of
the License at http://www.eclipse.org/legal/epl-v20.html
Software distributed under the License is distributed on an "AS
IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
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rights and limitations under the License.
Copyright (C) 2009-2010 Yoko Harada 
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either of the GNU General Public License Version 2 or later (the "GPL"),
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in which case the provisions of the GPL or the LGPL are applicable instead
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/**
 * **** BEGIN LICENSE BLOCK *****
 * Version: EPL 2.0/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Eclipse Public
 * 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.eclipse.org/legal/epl-v20.html
 *
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * Copyright (C) 2009-2010 Yoko Harada <yokolet@gmail.com>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the EPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
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package org.jruby.embed.io;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.CoderResult;
import java.nio.charset.CodingErrorAction;
import java.util.ArrayList;
import java.util.List;

import static com.headius.backport9.buffer.Buffers.clearBuffer;
import static com.headius.backport9.buffer.Buffers.flipBuffer;
import static com.headius.backport9.buffer.Buffers.limitBuffer;

A ReaderInputStream converts java.io.Reader to java.io.InputStream. The
ReaderInputStream reads data in a given Reader object into its internal buffer
so that users of this class can access the file that Reader read by using methods
defined in java.io.InputStream.
Author: Yoko Harada /**
 * A ReaderInputStream converts java.io.Reader to java.io.InputStream. The
 * ReaderInputStream reads data in a given Reader object into its internal buffer
 * so that users of this class can access the file that Reader read by using methods
 * defined in java.io.InputStream.
 *
 * @author Yoko Harada <yokolet@gmail.com>
 */
public class ReaderInputStream extends InputStream {

    private static final int DEFAULT_CHAR_BUFFER_SIZE = 8192;
    private static final int DEFAULT_BYTE_BUFFER_SIZE = 8192;
    private final Reader reader;
    private byte[] bytes = null;
    private int totalBytes = 0;
    private int position = 0;
    private int markedIndex = -1;
    private int readlimit = 0;
    private boolean isOpen = true;
    private CharsetEncoder encoder;
    private final Object lock = new Object();

    Creates ReaderInputStream from a given Reader type object with a default encoding.
Params: reader – java.io.Reader object to be read data from./**
     * Creates ReaderInputStream from a given Reader type object with a default encoding.
     *
     * @param reader java.io.Reader object to be read data from.
     */
    public ReaderInputStream(Reader reader) {
        this(reader, null);
    }

    Creates ReaderInputStream from a given Reader type object with a specifed encoding.
Params: reader – java.io.Reader object to be read data from.
encoding – an encoding of the created stream./**
     * Creates ReaderInputStream from a given Reader type object with a specifed encoding.
     *
     * @param reader java.io.Reader object to be read data from.
     * @param encoding an encoding of the created stream.
     */
    public ReaderInputStream(Reader reader, String encoding) {
        this.reader = reader;
        if (encoding == null) {
            if (reader instanceof InputStreamReader) {
                encoding = ((InputStreamReader) reader).getEncoding();
            } else {
                encoding = Charset.defaultCharset().name();
            }
        } else if (!Charset.isSupported(encoding)) {
            throw new IllegalArgumentException(encoding + " is not supported");
        }
        encoder = Charset.forName(encoding).newEncoder();
        encoder.onMalformedInput(CodingErrorAction.REPLACE);
        encoder.onUnmappableCharacter(CodingErrorAction.REPLACE);
        try {
            fillByteBuffer(reader);
        } catch (IOException ex) {
            throw new RuntimeException(ex);
        }
    }

    private void fillByteBuffer(Reader reader) throws IOException {
        CharBuffer cbuf = CharBuffer.allocate(DEFAULT_CHAR_BUFFER_SIZE);
        ByteBuffer bbuf = ByteBuffer.allocate(DEFAULT_BYTE_BUFFER_SIZE);
        List<byte[]> list = new ArrayList<byte[]>();
        while (true) {
            clearBuffer(cbuf);
            int size = reader.read(cbuf);
            if (size <= 0) {
                break;
            }
            limitBuffer(cbuf, cbuf.position());
            cbuf.rewind();
            boolean eof = false;
            while (!eof) {
                CoderResult cr = encoder.encode(cbuf, bbuf, eof);
                if (cr.isError()) {
                    cr.throwException();
                } else if (cr.isUnderflow()) {
                    appendBytes(list, bbuf);
                    eof = true;
                } else if (cr.isOverflow()) {
                    appendBytes(list, bbuf);
                    clearBuffer(bbuf);
                }
            }
        }
        getByteArray(list);
    }

    private void appendBytes(List<byte[]> list, ByteBuffer bb) {
        flipBuffer(bb);
        int length = bb.limit();
        totalBytes += length;
        byte[] dst = new byte[length];
        System.arraycopy(bb.array(), bb.position(), dst, 0, length);
        list.add(dst);
    }

    private void getByteArray(List<byte[]> list) {
        bytes = new byte[totalBytes];
        int index = 0;
        for (byte[] bb : list) {
            for (int i=0; i<bb.length; i++) {
                bytes[index++] = bb[i];
            }
        }
    }

    private void confirmOpen() throws IOException {
        if (!isOpen) {
            throw new IOException("This stream has been closed.");
        }
    }

    Returns an estimate of the number of bytes that can be read (or
skipped over) from this input stream without blocking by the next
invocation of a method for this input stream. The next invocation
might be the same thread or another thread.  A single read or skip of this
many bytes will not block, but may read or skip fewer bytes.
 Note that while some implementations of InputStream will return the total number of bytes in the stream, many will not. It is never correct to use the return value of this method to allocate a buffer intended to hold all data in this stream. 
 A subclass' implementation of this method may choose to throw an IOException if this input stream has been closed by invoking the close() method. 
 The available method for class InputStream always returns 0. 
Throws: IOException – if an I/O error occurs.
Returns:  an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking or 0 when it reaches the end of the input stream./**
     * Returns an estimate of the number of bytes that can be read (or
     * skipped over) from this input stream without blocking by the next
     * invocation of a method for this input stream. The next invocation
     * might be the same thread or another thread.  A single read or skip of this
     * many bytes will not block, but may read or skip fewer bytes.
     *
     * <p> Note that while some implementations of {@code InputStream} will return
     * the total number of bytes in the stream, many will not.  It is
     * never correct to use the return value of this method to allocate
     * a buffer intended to hold all data in this stream.
     *
     * <p> A subclass' implementation of this method may choose to throw an
     * {@link IOException} if this input stream has been closed by
     * invoking the {@link #close()} method.
     *
     * <p> The {@code available} method for class {@code InputStream} always
     * returns {@code 0}.
     *
     * @return     an estimate of the number of bytes that can be read (or skipped
     *             over) from this input stream without blocking or {@code 0} when
     *             it reaches the end of the input stream.
     * @exception  IOException if an I/O error occurs.
     */
    @Override
    public int available() throws IOException {
        synchronized (lock) {
            confirmOpen();
            if (bytes == null) {
                throw new IOException("This stream is not available.");
            }
            return totalBytes - position;
        }
    }

    Closes this input stream and releases any system resources associated
with the stream.
Throws: IOException –  if an I/O error occurs./**
     * Closes this input stream and releases any system resources associated
     * with the stream.
     *
     * @exception  IOException  if an I/O error occurs.
     */
    @Override
    public void close() throws IOException {
        synchronized (lock) {
            confirmOpen();
            isOpen = false;
            encoder = null;
            bytes = null;
            //reader.close();
        }
    }

    Marks the current position in this input stream. A subsequent call to
the reset method repositions this stream at the last marked
position so that subsequent reads re-read the same bytes.
 The readlimit arguments tells this input stream to
allow that many bytes to be read before the mark position gets
invalidated.
 The general contract of mark is that, if the method
markSupported returns true, the stream somehow
remembers all the bytes read after the call to mark and
stands ready to supply those same bytes again if and whenever the method
reset is called.  However, the stream is not required to
remember any data at all if more than readlimit bytes are
read from the stream before reset is called.
 Marking a closed stream should not have any effect on the stream.
 The mark method of InputStream does
nothing.
Params: readlimit –   the maximum limit of bytes that can be read before
                     the mark position becomes invalid.
See Also: InputStream.reset()/**
     * Marks the current position in this input stream. A subsequent call to
     * the <code>reset</code> method repositions this stream at the last marked
     * position so that subsequent reads re-read the same bytes.
     *
     * <p> The <code>readlimit</code> arguments tells this input stream to
     * allow that many bytes to be read before the mark position gets
     * invalidated.
     *
     * <p> The general contract of <code>mark</code> is that, if the method
     * <code>markSupported</code> returns <code>true</code>, the stream somehow
     * remembers all the bytes read after the call to <code>mark</code> and
     * stands ready to supply those same bytes again if and whenever the method
     * <code>reset</code> is called.  However, the stream is not required to
     * remember any data at all if more than <code>readlimit</code> bytes are
     * read from the stream before <code>reset</code> is called.
     *
     * <p> Marking a closed stream should not have any effect on the stream.
     *
     * <p> The <code>mark</code> method of <code>InputStream</code> does
     * nothing.
     *
     * @param   readlimit   the maximum limit of bytes that can be read before
     *                      the mark position becomes invalid.
     * @see     java.io.InputStream#reset()
     */
    @Override
    public synchronized void mark(int readlimit) {
        if (readlimit < 0) {
            throw new IllegalArgumentException("Read limit < 0");
        }
        synchronized (lock) {
            if (isOpen) {
                this.readlimit = readlimit;
                markedIndex = position;
            }
        }
    }

    Tests if this input stream supports the mark and
reset methods. Whether or not mark and
reset are supported is an invariant property of a
particular input stream instance.
See Also: InputStream.mark(int)
InputStream.reset()
Returns:  true if this stream instance supports the mark
         and reset methods; false otherwise./**
     * Tests if this input stream supports the <code>mark</code> and
     * <code>reset</code> methods. Whether or not <code>mark</code> and
     * <code>reset</code> are supported is an invariant property of a
     * particular input stream instance.
     *
     * @return  <code>true</code> if this stream instance supports the mark
     *          and reset methods; <code>false</code> otherwise.
     * @see     java.io.InputStream#mark(int)
     * @see     java.io.InputStream#reset()
     */
    @Override
    public boolean markSupported() {
        return true;
    }

    Reads the next byte of data from the input stream. The value byte is
returned as an int in the range 0 to
255. If no byte is available because the end of the stream
has been reached, the value -1 is returned. This method
blocks until input data is available, the end of the stream is detected,
or an exception is thrown.
 A subclass must provide an implementation of this method.
Throws: IOException –  if an I/O error occurs.
Returns:     the next byte of data, or -1 if the end of the
            stream is reached./**
     * Reads the next byte of data from the input stream. The value byte is
     * returned as an <code>int</code> in the range <code>0</code> to
     * <code>255</code>. If no byte is available because the end of the stream
     * has been reached, the value <code>-1</code> is returned. This method
     * blocks until input data is available, the end of the stream is detected,
     * or an exception is thrown.
     *
     * <p> A subclass must provide an implementation of this method.
     *
     * @return     the next byte of data, or <code>-1</code> if the end of the
     *             stream is reached.
     * @exception  IOException  if an I/O error occurs.
     */
    @Override
    public int read() throws IOException {
        synchronized (lock) {
            confirmOpen();
            if (position >= totalBytes) {
                return -1;
            } else {
                return bytes[position++];
            }
        }
    }

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

    Reads up to len bytes of data from the input stream into
an array of bytes.  An attempt is made to read as many as
len bytes, but a smaller number may be read.
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.
 If len is zero, then no bytes are read and
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 -1 is returned; otherwise, at least one
byte is read and stored into b.
 The first byte read is stored into element b[off], the
next one into b[off+1], and so on. The number of bytes read
is, at most, equal to len. Let k be the number of
bytes actually read; these bytes will be stored in elements
b[off] through b[off+k-1],
leaving elements b[off+k] through
b[off+len-1] unaffected.
 In every case, elements b[0] through
b[off] and elements b[off+len] through
b[b.length-1] are unaffected.
 The read(b, off, len) method
for class InputStream simply calls the method
read() repeatedly. If the first such call results in an
IOException, that exception is returned from the call to
the read(b, off, len) method.  If
any subsequent call to read() results in a
IOException, the exception is caught and treated as if it
were end of file; the bytes read up to that point are stored into
b and the number of bytes read before the exception
occurred is returned. The default implementation of this method blocks
until the requested amount of input data len has been read,
end of file is detected, or an exception is thrown. Subclasses are encouraged
to provide a more efficient implementation of this method.
Params: b –     the buffer into which the data is read.
off –   the start offset in array b
                  at which the data is written.
len –   the maximum number of bytes to read.
Throws: IOException – If the first byte cannot be read for any reason
other than end of file, or if the input stream has been closed, or if
some other I/O error occurs.
NullPointerException – If b is null.
IndexOutOfBoundsException – If off is negative,
len is negative, or len is greater than
b.length - off
See Also: InputStream.read()
Returns:     the total number of bytes read into the buffer, or
            -1 if there is no more data because the end of
            the stream has been reached./**
     * Reads up to <code>len</code> bytes of data from the input stream into
     * an array of bytes.  An attempt is made to read as many as
     * <code>len</code> bytes, but a smaller number may be read.
     * 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</code> is zero, then no bytes are read and
     * <code>0</code> 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</code> is returned; otherwise, at least one
     * byte is read and stored into <code>b</code>.
     *
     * <p> The first byte read is stored into element <code>b[off]</code>, the
     * next one into <code>b[off+1]</code>, and so on. The number of bytes read
     * is, at most, equal to <code>len</code>. Let <i>k</i> be the number of
     * bytes actually read; these bytes will be stored in elements
     * <code>b[off]</code> through <code>b[off+</code><i>k</i><code>-1]</code>,
     * leaving elements <code>b[off+</code><i>k</i><code>]</code> through
     * <code>b[off+len-1]</code> unaffected.
     *
     * <p> In every case, elements <code>b[0]</code> through
     * <code>b[off]</code> and elements <code>b[off+len]</code> through
     * <code>b[b.length-1]</code> are unaffected.
     *
     * <p> The <code>read(b,</code> <code>off,</code> <code>len)</code> method
     * for class <code>InputStream</code> simply calls the method
     * <code>read()</code> repeatedly. If the first such call results in an
     * <code>IOException</code>, that exception is returned from the call to
     * the <code>read(b,</code> <code>off,</code> <code>len)</code> method.  If
     * any subsequent call to <code>read()</code> results in a
     * <code>IOException</code>, the exception is caught and treated as if it
     * were end of file; the bytes read up to that point are stored into
     * <code>b</code> and the number of bytes read before the exception
     * occurred is returned. The default implementation of this method blocks
     * until the requested amount of input data <code>len</code> has been read,
     * end of file is detected, or an exception is thrown. Subclasses are encouraged
     * to provide a more efficient implementation of this method.
     *
     * @param      b     the buffer into which the data is read.
     * @param      off   the start offset in array <code>b</code>
     *                   at which the data is written.
     * @param      len   the maximum number of bytes to read.
     * @return     the total number of bytes read into the buffer, or
     *             <code>-1</code> if there is no more data because the end of
     *             the stream has been reached.
     * @exception  IOException If the first byte cannot be read for any reason
     * other than end of file, or if the input stream has been closed, or if
     * some other I/O error occurs.
     * @exception  NullPointerException If <code>b</code> is <code>null</code>.
     * @exception  IndexOutOfBoundsException If <code>off</code> is negative,
     * <code>len</code> is negative, or <code>len</code> is greater than
     * <code>b.length - off</code>
     * @see        java.io.InputStream#read()
     */
    @Override
    public int read(byte[] b, int off, int len) throws IOException {
        synchronized (lock) {
            confirmOpen();
            if (len == 0) {
                return 0;
            }
            if (position >= totalBytes) {
                return -1;
            }
            if (off < 0 || off > totalBytes || len < 0) {
                throw new IllegalArgumentException("Either one of, or both of off and len are invalid.");
            }
            int start = position + off;
            start = start < totalBytes ? start : totalBytes - 1;
            int end = start + len;
            end = end < totalBytes ? end : totalBytes - 1;
            int actuallyRead = Math.min((end - start) + 1, len);
            System.arraycopy(bytes, start, b, 0, actuallyRead);
            position += actuallyRead;
            return actuallyRead;

        }
    }

    Repositions this stream to the position at the time the
mark method was last called on this input stream.
 The general contract of reset is:

 If the method markSupported returns
true, then:
     If the method mark has not been called since
    the stream was created, or the number of bytes read from the stream
    since mark was last called is larger than the argument
    to mark at that last call, then an
    IOException might be thrown.
    
 If such an IOException is not thrown, then the
    stream is reset to a state such that all the bytes read since the
    most recent call to mark (or since the start of the
    file, if mark has not been called) will be resupplied
    to subsequent callers of the read method, followed by
    any bytes that otherwise would have been the next input data as of
    the time of the call to reset. 
 If the method markSupported returns
false, then:
     The call to reset may throw an
    IOException.
    
 If an IOException is not thrown, then the stream
    is reset to a fixed state that depends on the particular type of the
    input stream and how it was created. The bytes that will be supplied
    to subsequent callers of the read method depend on the
    particular type of the input stream. 
Throws: IOException –  if this stream has not been marked or if the
              mark has been invalidated.
See Also: InputStream.mark(int)
IOException/**
     * Repositions this stream to the position at the time the
     * <code>mark</code> method was last called on this input stream.
     *
     * <p> The general contract of <code>reset</code> is:
     *
     * <p><ul>
     *
     * <li> If the method <code>markSupported</code> returns
     * <code>true</code>, then:
     *
     *     <ul><li> If the method <code>mark</code> has not been called since
     *     the stream was created, or the number of bytes read from the stream
     *     since <code>mark</code> was last called is larger than the argument
     *     to <code>mark</code> at that last call, then an
     *     <code>IOException</code> might be thrown.
     *
     *     <li> If such an <code>IOException</code> is not thrown, then the
     *     stream is reset to a state such that all the bytes read since the
     *     most recent call to <code>mark</code> (or since the start of the
     *     file, if <code>mark</code> has not been called) will be resupplied
     *     to subsequent callers of the <code>read</code> method, followed by
     *     any bytes that otherwise would have been the next input data as of
     *     the time of the call to <code>reset</code>. </ul>
     *
     * <li> If the method <code>markSupported</code> returns
     * <code>false</code>, then:
     *
     *     <ul><li> The call to <code>reset</code> may throw an
     *     <code>IOException</code>.
     *
     *     <li> If an <code>IOException</code> is not thrown, then the stream
     *     is reset to a fixed state that depends on the particular type of the
     *     input stream and how it was created. The bytes that will be supplied
     *     to subsequent callers of the <code>read</code> method depend on the
     *     particular type of the input stream. </ul></ul>
     *
     * @exception  IOException  if this stream has not been marked or if the
     *               mark has been invalidated.
     * @see     java.io.InputStream#mark(int)
     * @see     java.io.IOException
     */
    @Override
    public synchronized void reset() throws IOException {
        synchronized (lock) {
            if (!isOpen) {
                throw new IOException("This stream has been closed.");
            }
            if (markedIndex < 0) {
                throw new IOException("This stream is not marked.");
            }
            if ((position - markedIndex) > readlimit) {
                throw new IOException("Mark is invalidated.");
            }
            position = markedIndex;
        }
    }

    Skips over and discards n bytes of data from this input
stream. The skip method may, for a variety of reasons, end
up skipping over some smaller number of bytes, possibly 0.
This may result from any of a number of conditions; reaching end of file
before n bytes have been skipped is only one possibility.
The actual number of bytes skipped is returned.  If n is
negative, no bytes are skipped.
Params: n –   the number of bytes to be skipped.
Throws: IOException –  if the stream does not support seek,
                         or if some other I/O error occurs.
Returns:     the actual number of bytes skipped./**
     * Skips over and discards <code>n</code> bytes of data from this input
     * stream. The <code>skip</code> method may, for a variety of reasons, end
     * up skipping over some smaller number of bytes, possibly <code>0</code>.
     * This may result from any of a number of conditions; reaching end of file
     * before <code>n</code> bytes have been skipped is only one possibility.
     * The actual number of bytes skipped is returned.  If <code>n</code> is
     * negative, no bytes are skipped.
     *
     * @param      n   the number of bytes to be skipped.
     * @return     the actual number of bytes skipped.
     * @exception  IOException  if the stream does not support seek,
     *                          or if some other I/O error occurs.
     */
    @Override
    public long skip(long n) throws IOException {
        if (n < 0L) {
            throw new IllegalArgumentException("Negarive skip");
        }
        synchronized (lock) {
            if (!isOpen) {
                throw new IOException("This stream has been closed.");
            }
            long skipped;
            if ((totalBytes - position) < n) {
                skipped = totalBytes - position;
                position = totalBytes;
            } else {
                skipped = n;
                position += n;
            }
            return skipped;
        }
    }
}
Throws:	IOException – if an I/O error occurs.
Returns:	an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking or `0` when it reaches the end of the input stream.
Params:	readlimit – the maximum limit of bytes that can be read before the mark position becomes invalid.
See Also:	InputStream.reset()
See Also:	InputStream.mark(int) InputStream.reset()
Returns:	`true` if this stream instance supports the mark and reset methods; `false` otherwise.
Params:	b – the buffer into which the data is read.
Throws:	IOException – If the first byte cannot be read for any reason other than the end of the file, if the input stream has been closed, or if some other I/O error occurs. NullPointerException – if `b` is `null`.
See Also:	InputStream.read(byte[], int, int)
Returns:	the total number of bytes read into the buffer, or `-1` is there is no more data because the end of the stream has been reached.
Throws:	IOException – if this stream has not been marked or if the mark has been invalidated.
See Also:	InputStream.mark(int) IOException
Params:	n – the number of bytes to be skipped.
Throws:	IOException – if the stream does not support seek, or if some other I/O error occurs.
Returns:	the actual number of bytes skipped.
/

org.jruby/ jruby-core/ 9.2.14.0/ org/jruby/embed/io/ReaderInputStream.java
