com.phloc.commons.io.streams.NonBlockingBufferedReader Maven / Gradle / Ivy
/**
* Copyright (C) 2006-2015 phloc systems
* http://www.phloc.com
* office[at]phloc[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.phloc.commons.io.streams;
import java.io.IOException;
import java.io.Reader;
import javax.annotation.Nonnegative;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import com.phloc.commons.ValueEnforcer;
/**
* A non-synchronized copy of the class {@link java.io.BufferedReader}.
*
* @author Philip Helger
* @see java.io.BufferedReader
*/
public class NonBlockingBufferedReader extends Reader
{
private static final int INVALIDATED = -2;
private static final int UNMARKED = -1;
private static final int DEFAULT_CHAR_BUFFER_SIZE = 8192;
private static final int DEFAULT_EXPECTED_LINE_LENGTH = 80;
private Reader m_aReader;
private char [] m_aBuf;
private int m_nChars;
private int m_nNextCharIndex;
private int m_nMarkedChar = UNMARKED;
/** Valid only when markedChar > 0 */
private int m_nReadAheadLimit = 0;
/** If the next character is a line feed, skip it */
private boolean m_bSkipLF = false;
/** The skipLF flag when the mark was set */
private boolean m_bMarkedSkipLF = false;
/**
* Creates a buffering character-input stream that uses a default-sized input
* buffer.
*
* @param aReader
* A Reader
*/
public NonBlockingBufferedReader (@Nonnull final Reader aReader)
{
this (aReader, DEFAULT_CHAR_BUFFER_SIZE);
}
/**
* Creates a buffering character-input stream that uses an input buffer of the
* specified size.
*
* @param aReader
* A Reader
* @param nSize
* Input-buffer size
* @exception IllegalArgumentException
* If size is <= 0
*/
public NonBlockingBufferedReader (@Nonnull final Reader aReader, @Nonnegative final int nSize)
{
super (aReader);
ValueEnforcer.isGT0 (nSize, "Size");
this.m_aReader = aReader;
this.m_aBuf = new char [nSize];
}
/**
* Checks to make sure that the stream has not been closed
*
* @throws IOException
* If the reader is not open
*/
private void _ensureOpen () throws IOException
{
if (this.m_aReader == null)
throw new IOException ("Stream closed");
}
/**
* Fills the input buffer, taking the mark into account if it is valid.
*
* @throws IOException
* In case reading fails
*/
private void _fill () throws IOException
{
int nDstOfs = 0;
if (this.m_nMarkedChar > UNMARKED)
{
// Marked
final int nDelta = this.m_nNextCharIndex - this.m_nMarkedChar;
if (nDelta >= this.m_nReadAheadLimit)
{
// Gone past read-ahead limit: Invalidate mark
this.m_nMarkedChar = INVALIDATED;
this.m_nReadAheadLimit = 0;
}
else
{
if (this.m_nReadAheadLimit <= this.m_aBuf.length)
{
// Shuffle in the current buffer
System.arraycopy (this.m_aBuf, this.m_nMarkedChar, this.m_aBuf, 0, nDelta);
this.m_nMarkedChar = 0;
nDstOfs = nDelta;
}
else
{
// Reallocate buffer to accommodate read-ahead limit
final char [] aNewBuf = new char [this.m_nReadAheadLimit];
System.arraycopy (this.m_aBuf, this.m_nMarkedChar, aNewBuf, 0, nDelta);
this.m_aBuf = aNewBuf;
this.m_nMarkedChar = 0;
nDstOfs = nDelta;
}
this.m_nNextCharIndex = nDelta;
this.m_nChars = nDelta;
}
}
int nBytesRead;
do
{
nBytesRead = this.m_aReader.read (this.m_aBuf, nDstOfs, this.m_aBuf.length - nDstOfs);
} while (nBytesRead == 0);
if (nBytesRead > 0)
{
this.m_nChars = nDstOfs + nBytesRead;
this.m_nNextCharIndex = nDstOfs;
}
}
/**
* Reads a single character.
*
* @return The character read, as an integer in the range 0 to 65535 (
* 0x00-0xffff), or -1 if the end of the stream has been
* reached
* @exception IOException
* If an I/O error occurs
*/
@Override
public int read () throws IOException
{
_ensureOpen ();
while (true)
{
if (this.m_nNextCharIndex >= this.m_nChars)
{
_fill ();
if (this.m_nNextCharIndex >= this.m_nChars)
return -1;
}
if (this.m_bSkipLF)
{
this.m_bSkipLF = false;
if (this.m_aBuf[this.m_nNextCharIndex] == '\n')
{
this.m_nNextCharIndex++;
continue;
}
}
return this.m_aBuf[this.m_nNextCharIndex++];
}
}
/**
* Reads characters into a portion of an array, reading from the underlying
* stream if necessary.
*
* @param aBuf
* The buffer to be filled
* @param nOfs
* The offset to start reading
* @param nLen
* The number of bytes to read
* @return The number of bytes read
* @throws IOException
* in case reading fails
*/
private int _internalRead (final char [] aBuf, final int nOfs, final int nLen) throws IOException
{
if (this.m_nNextCharIndex >= this.m_nChars)
{
/*
* If the requested length is at least as large as the buffer, and if
* there is no mark/reset activity, and if line feeds are not being
* skipped, do not bother to copy the characters into the local buffer. In
* this way buffered streams will cascade harmlessly.
*/
if (nLen >= this.m_aBuf.length && this.m_nMarkedChar <= UNMARKED && !this.m_bSkipLF)
return this.m_aReader.read (aBuf, nOfs, nLen);
_fill ();
}
if (this.m_nNextCharIndex >= this.m_nChars)
return -1;
if (this.m_bSkipLF)
{
this.m_bSkipLF = false;
if (this.m_aBuf[this.m_nNextCharIndex] == '\n')
{
this.m_nNextCharIndex++;
if (this.m_nNextCharIndex >= this.m_nChars)
_fill ();
if (this.m_nNextCharIndex >= this.m_nChars)
return -1;
}
}
final int nBytesRead = Math.min (nLen, this.m_nChars - this.m_nNextCharIndex);
System.arraycopy (this.m_aBuf, this.m_nNextCharIndex, aBuf, nOfs, nBytesRead);
this.m_nNextCharIndex += nBytesRead;
return nBytesRead;
}
/**
* Reads characters into a portion of an array.
*
* This method implements the general contract of the corresponding
* {@link Reader#read(char[], int, int) read} method of the
* {@link Reader} class. As an additional convenience, it
* attempts to read as many characters as possible by repeatedly invoking the
* read method of the underlying stream. This iterated
* read continues until one of the following conditions becomes
* true:
*
* - The specified number of characters have been read,
*
- The
read method of the underlying stream returns
* -1, indicating end-of-file, or
* - The
ready method of the underlying stream returns
* false, indicating that further input requests would block.
*
* If the first read on the underlying stream returns
* -1 to indicate end-of-file then this method returns
* -1. Otherwise this method returns the number of characters
* actually read.
*
* Subclasses of this class are encouraged, but not required, to attempt to
* read as many characters as possible in the same fashion.
*
* Ordinarily this method takes characters from this stream's character
* buffer, filling it from the underlying stream as necessary. If, however,
* the buffer is empty, the mark is not valid, and the requested length is at
* least as large as the buffer, then this method will read characters
* directly from the underlying stream into the given array. Thus redundant
* NonBlockingBufferedReaders will not copy data unnecessarily.
*
* @param cbuf
* Destination buffer
* @param nOfs
* Offset at which to start storing 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
public int read (final char [] cbuf, final int nOfs, final int nLen) throws IOException
{
_ensureOpen ();
ValueEnforcer.isArrayOfsLen (cbuf, nOfs, nLen);
if (nLen == 0)
return 0;
// Main read
int n = _internalRead (cbuf, nOfs, nLen);
if (n <= 0)
return n;
while (n < nLen && this.m_aReader.ready ())
{
final int n1 = _internalRead (cbuf, nOfs + n, nLen - n);
if (n1 <= 0)
break;
n += n1;
}
return n;
}
/**
* Reads a line of text. A line is considered to be terminated by any one of a
* line feed ('\n'), a carriage return ('\r'), or a carriage return followed
* immediately by a linefeed.
*
* @return A String containing the contents of the line, not including any
* line-termination characters, or null if the end of the stream has
* been reached
* @exception IOException
* If an I/O error occurs
*/
@Nullable
public String readLine () throws IOException
{
StringBuilder aSB = null;
int nStartChar;
_ensureOpen ();
boolean bOmitLF = this.m_bSkipLF;
while (true)
{
if (this.m_nNextCharIndex >= this.m_nChars)
_fill ();
if (this.m_nNextCharIndex >= this.m_nChars)
{
/* EOF */
if (aSB != null && aSB.length () > 0)
return aSB.toString ();
return null;
}
boolean bEOL = false;
char cLast = 0;
int nIndex;
/* Skip a leftover '\n', if necessary */
if (bOmitLF && this.m_aBuf[this.m_nNextCharIndex] == '\n')
this.m_nNextCharIndex++;
this.m_bSkipLF = false;
bOmitLF = false;
for (nIndex = this.m_nNextCharIndex; nIndex < this.m_nChars; nIndex++)
{
cLast = this.m_aBuf[nIndex];
if (cLast == '\n' || cLast == '\r')
{
bEOL = true;
break;
}
}
nStartChar = this.m_nNextCharIndex;
this.m_nNextCharIndex = nIndex;
if (bEOL)
{
String sStr;
if (aSB == null)
sStr = new String (this.m_aBuf, nStartChar, nIndex - nStartChar);
else
{
aSB.append (this.m_aBuf, nStartChar, nIndex - nStartChar);
sStr = aSB.toString ();
}
this.m_nNextCharIndex++;
if (cLast == '\r')
this.m_bSkipLF = true;
return sStr;
}
if (aSB == null)
aSB = new StringBuilder (DEFAULT_EXPECTED_LINE_LENGTH);
aSB.append (this.m_aBuf, nStartChar, nIndex - nStartChar);
}
}
/**
* Skips characters.
*
* @param nBytes
* The number of characters to skip
* @return The number of characters actually skipped
* @exception IllegalArgumentException
* If n is negative.
* @exception IOException
* If an I/O error occurs
*/
@Override
public long skip (final long nBytes) throws IOException
{
ValueEnforcer.isGE0 (nBytes, "Bytes");
_ensureOpen ();
long nRest = nBytes;
while (nRest > 0)
{
if (this.m_nNextCharIndex >= this.m_nChars)
_fill ();
if (this.m_nNextCharIndex >= this.m_nChars)
{
// EOF
break;
}
if (this.m_bSkipLF)
{
this.m_bSkipLF = false;
if (this.m_aBuf[this.m_nNextCharIndex] == '\n')
this.m_nNextCharIndex++;
}
final int d = this.m_nChars - this.m_nNextCharIndex;
if (nRest <= d)
{
this.m_nNextCharIndex += nRest;
nRest = 0;
break;
}
nRest -= d;
this.m_nNextCharIndex = this.m_nChars;
}
return nBytes - nRest;
}
/**
* Tells whether this stream is ready to be read. A buffered character stream
* is ready if the buffer is not empty, or if the underlying character stream
* is ready.
*
* @return true if the reader is ready
* @exception IOException
* If an I/O error occurs
*/
@Override
public boolean ready () throws IOException
{
_ensureOpen ();
/*
* If newline needs to be skipped and the next char to be read is a newline
* character, then just skip it right away.
*/
if (this.m_bSkipLF)
{
/*
* Note that in.ready() will return true if and only if the next read on
* the stream will not block.
*/
if (this.m_nNextCharIndex >= this.m_nChars && this.m_aReader.ready ())
_fill ();
if (this.m_nNextCharIndex < this.m_nChars)
{
if (this.m_aBuf[this.m_nNextCharIndex] == '\n')
this.m_nNextCharIndex++;
this.m_bSkipLF = false;
}
}
return this.m_nNextCharIndex < this.m_nChars || this.m_aReader.ready ();
}
/**
* 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
* attempt to reposition the stream to this point.
*
* @param nReadAheadLimit
* Limit on the number of characters that may be read while still
* preserving the mark. An attempt to reset the stream after reading
* characters up to this limit or beyond may fail. A limit value larger
* than the size of the input buffer will cause a new buffer to be
* allocated whose size is no smaller than limit. Therefore large
* values should be used with care.
* @exception IllegalArgumentException
* If readAheadLimit is < 0
* @exception IOException
* If an I/O error occurs
*/
@Override
public void mark (@Nonnegative final int nReadAheadLimit) throws IOException
{
ValueEnforcer.isGE0 (nReadAheadLimit, "ReadAheadLimit");
_ensureOpen ();
this.m_nReadAheadLimit = nReadAheadLimit;
this.m_nMarkedChar = this.m_nNextCharIndex;
this.m_bMarkedSkipLF = this.m_bSkipLF;
}
/**
* Resets the stream to the most recent mark.
*
* @exception IOException
* If the stream has never been marked, or if the mark has been
* invalidated
*/
@Override
public void reset () throws IOException
{
_ensureOpen ();
if (this.m_nMarkedChar < 0)
throw new IOException (this.m_nMarkedChar == INVALIDATED ? "Mark invalid" : "Stream not marked");
this.m_nNextCharIndex = this.m_nMarkedChar;
this.m_bSkipLF = this.m_bMarkedSkipLF;
}
@Override
public void close () throws IOException
{
if (this.m_aReader != null)
{
this.m_aReader.close ();
this.m_aReader = null;
this.m_aBuf = null;
}
}
}