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/*
* Copyright (C) 2014-2024 Philip Helger (www.helger.com)
* philip[at]helger[dot]com
*
* 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.helger.commons.io.stream;
import java.io.IOException;
import java.io.Reader;
import javax.annotation.CheckForSigned;
import javax.annotation.Nonnegative;
import javax.annotation.Nonnull;
import javax.annotation.concurrent.NotThreadSafe;
import com.helger.commons.ValueEnforcer;
import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
/**
* A non-synchronized copy of the class {@link java.io.StringReader}.
* Note: super class {@link Reader} uses the lock object internally only for
* long skip(long n) and as this method is overwritten in here, the
* lock is never used.
*
* @author Philip Helger
* @see java.io.StringReader
*/
@NotThreadSafe
public class NonBlockingStringReader extends Reader
{
private char [] m_aChars;
private final int m_nLength;
private int m_nNext;
private int m_nMark;
public NonBlockingStringReader (@Nonnull final char [] aChars)
{
this (aChars, 0, aChars.length);
}
@SuppressFBWarnings ("EI_EXPOSE_REP2")
public NonBlockingStringReader (@Nonnull final char [] aChars, @Nonnegative final int nOfs, @Nonnegative final int nLen)
{
ValueEnforcer.isArrayOfsLen (aChars, nOfs, nLen);
m_aChars = aChars;
m_nLength = nLen;
m_nNext = m_nMark = nOfs;
}
/**
* Creates a new string reader.
*
* @param sStr
* String providing the character stream. May not be null.
*/
public NonBlockingStringReader (@Nonnull final String sStr)
{
this (sStr.toCharArray (), 0, sStr.length ());
}
public NonBlockingStringReader (@Nonnull final String sStr, @Nonnegative final int nOfs, @Nonnegative final int nLen)
{
this (sStr.toCharArray (), nOfs, nLen);
}
/**
* Check to make sure that the stream has not been closed
*
* @throws IOException
* When the string is closed
*/
private void _ensureOpen () throws IOException
{
if (m_aChars == null)
throw new IOException ("Stream closed");
}
/**
* Reads a single character.
*
* @return The character read, or -1 if the end of the stream has been reached
* @exception IOException
* If an I/O error occurs
*/
@Override
@CheckForSigned
public int read () throws IOException
{
_ensureOpen ();
if (m_nNext >= m_nLength)
return -1;
return m_aChars[m_nNext++];
}
/**
* Reads characters into a portion of an array.
*
* @param aBuf
* Destination buffer
* @param nOfs
* Offset at which to start writing characters
* @param nLen
* Maximum number of characters to read
* @return The number of characters read, or -1 if the end of the stream has
* been reached
* @exception IOException
* If an I/O error occurs
*/
@Override
@CheckForSigned
public int read (@Nonnull final char [] aBuf, @Nonnegative final int nOfs, @Nonnegative final int nLen) throws IOException
{
_ensureOpen ();
ValueEnforcer.isArrayOfsLen (aBuf, nOfs, nLen);
if (nLen == 0)
return 0;
if (m_nNext >= m_nLength)
return -1;
final int nChars = Math.min (m_nLength - m_nNext, nLen);
System.arraycopy (m_aChars, m_nNext, aBuf, nOfs, nChars);
m_nNext += nChars;
return nChars;
}
/**
* Skips the specified number of characters in the stream. Returns the number
* of characters that were skipped.
*
*
* @param nCharsToSkip
* The parameter may be negative, even though the skip
* method of the {@link Reader} superclass throws an exception in this
* case. Negative values of the parameter cause the stream to skip
* backwards. Negative return values indicate a skip backwards. It is
* not possible to skip backwards past the beginning of the string.
* @return If the entire string has been read or skipped, then this method has
* no effect and always returns 0.
* @exception IOException
* If an I/O error occurs
*/
@Override
public long skip (final long nCharsToSkip) throws IOException
{
_ensureOpen ();
if (m_nNext >= m_nLength)
return 0;
// Bound skip by beginning and end of the source
long n = Math.min ((long) m_nLength - m_nNext, nCharsToSkip);
n = Math.max (-m_nNext, n);
m_nNext += (int) n;
return n;
}
/**
* Tells whether this stream is ready to be read.
*
* @return true if the next read() is guaranteed not to block for
* input
* @exception IOException
* If the stream is closed
*/
@Override
public boolean ready () throws IOException
{
_ensureOpen ();
return true;
}
/**
* Tells whether this stream supports the mark() operation, which it does.
*
* @return always true
*/
@Override
public boolean markSupported ()
{
return true;
}
/**
* Marks the present position in the stream. Subsequent calls to reset() will
* reposition the stream to this point.
*
* @param nReadAheadLimit
* Limit on the number of characters that may be read while still
* preserving the mark. Because the stream's input comes from a string,
* there is no actual limit, so this argument must not be negative, but
* is otherwise ignored.
* @exception IllegalArgumentException
* If readAheadLimit is < 0
* @exception IOException
* If an I/O error occurs
*/
@Override
public void mark (final int nReadAheadLimit) throws IOException
{
ValueEnforcer.isGE0 (nReadAheadLimit, "ReadAheadLimit");
_ensureOpen ();
m_nMark = m_nNext;
}
/**
* Resets the stream to the most recent mark, or to the beginning of the
* string if it has never been marked.
*
* @exception IOException
* If an I/O error occurs
*/
@Override
public void reset () throws IOException
{
_ensureOpen ();
m_nNext = m_nMark;
}
/**
* Closes the stream and releases any system resources associated with it.
* Once the stream has been closed, further read(), ready(), mark(), or
* reset() invocations will throw an IOException. Closing a previously closed
* stream has no effect.
*/
@Override
public void close ()
{
m_aChars = null;
}
}