panda.io.stream.CharSequenceInputStream Maven / Gradle / Ivy
package panda.io.stream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.CharacterCodingException;
import java.nio.charset.Charset;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.CoderResult;
import java.nio.charset.CodingErrorAction;
import panda.io.Streams;
/**
* {@link InputStream} implementation that can read from String, StringBuffer, StringBuilder or
* CharBuffer.
*
* Note: Supports {@link #mark(int)} and {@link #reset()}.
*/
public class CharSequenceInputStream extends InputStream {
private static final int BUFFER_SIZE = 2048;
private static final int NO_MARK = -1;
private final CharsetEncoder encoder;
private final CharBuffer cbuf;
private final ByteBuffer bbuf;
private int mark_cbuf; // position in cbuf
private int mark_bbuf; // position in bbuf
/**
* Constructor.
*
* @param cs the input character sequence
* @param charset the character set name to use
* @param bufferSize the buffer size to use.
* @throws IllegalArgumentException if the buffer is not large enough to hold a complete
* character
*/
public CharSequenceInputStream(final CharSequence cs, final Charset charset, final int bufferSize) {
super();
this.encoder = charset.newEncoder().onMalformedInput(CodingErrorAction.REPLACE)
.onUnmappableCharacter(CodingErrorAction.REPLACE);
// Ensure that buffer is long enough to hold a complete character
final float maxBytesPerChar = encoder.maxBytesPerChar();
if (bufferSize < maxBytesPerChar) {
throw new IllegalArgumentException("Buffer size " + bufferSize + " is less than maxBytesPerChar "
+ maxBytesPerChar);
}
this.bbuf = ByteBuffer.allocate(bufferSize);
this.bbuf.flip();
this.cbuf = CharBuffer.wrap(cs);
this.mark_cbuf = NO_MARK;
this.mark_bbuf = NO_MARK;
}
/**
* Constructor, calls {@link #CharSequenceInputStream(CharSequence, Charset, int)}.
*
* @param cs the input character sequence
* @param charset the character set name to use
* @param bufferSize the buffer size to use.
* @throws IllegalArgumentException if the buffer is not large enough to hold a complete
* character
*/
public CharSequenceInputStream(final CharSequence cs, final String charset, final int bufferSize) {
this(cs, Charset.forName(charset), bufferSize);
}
/**
* Constructor, calls {@link #CharSequenceInputStream(CharSequence, Charset, int)} with a buffer
* size of 2048.
*
* @param cs the input character sequence
* @param charset the character set name to use
* @throws IllegalArgumentException if the buffer is not large enough to hold a complete
* character
*/
public CharSequenceInputStream(final CharSequence cs, final Charset charset) {
this(cs, charset, BUFFER_SIZE);
}
/**
* Constructor, calls {@link #CharSequenceInputStream(CharSequence, String, int)} with a buffer
* size of 2048.
*
* @param cs the input character sequence
* @param charset the character set name to use
* @throws IllegalArgumentException if the buffer is not large enough to hold a complete
* character
*/
public CharSequenceInputStream(final CharSequence cs, final String charset) {
this(cs, charset, BUFFER_SIZE);
}
/**
* Fills the byte output buffer from the input char buffer.
*
* @throws CharacterCodingException an error encoding data
*/
private void fillBuffer() throws CharacterCodingException {
this.bbuf.compact();
final CoderResult result = this.encoder.encode(this.cbuf, this.bbuf, true);
if (result.isError()) {
result.throwException();
}
this.bbuf.flip();
}
@Override
public int read(final byte[] b, int off, int len) throws IOException {
if (b == null) {
throw new NullPointerException("Byte array is null");
}
if (len < 0 || (off + len) > b.length) {
throw new IndexOutOfBoundsException("Array Size=" + b.length + ", offset=" + off + ", length=" + len);
}
if (len == 0) {
return 0; // must return 0 for zero length read
}
if (!this.bbuf.hasRemaining() && !this.cbuf.hasRemaining()) {
return Streams.EOF;
}
int bytesRead = 0;
while (len > 0) {
if (this.bbuf.hasRemaining()) {
final int chunk = Math.min(this.bbuf.remaining(), len);
this.bbuf.get(b, off, chunk);
off += chunk;
len -= chunk;
bytesRead += chunk;
}
else {
fillBuffer();
if (!this.bbuf.hasRemaining() && !this.cbuf.hasRemaining()) {
break;
}
}
}
return bytesRead == 0 && !this.cbuf.hasRemaining() ? Streams.EOF : bytesRead;
}
@Override
public int read() throws IOException {
for (;;) {
if (this.bbuf.hasRemaining()) {
return this.bbuf.get() & 0xFF;
}
else {
fillBuffer();
if (!this.bbuf.hasRemaining() && !this.cbuf.hasRemaining()) {
return Streams.EOF;
}
}
}
}
@Override
public int read(final byte[] b) throws IOException {
return read(b, 0, b.length);
}
@Override
public long skip(long n) throws IOException {
/*
* This could be made more efficient by using position to skip within the current buffer.
*/
long skipped = 0;
while (n > 0 && available() > 0) {
this.read();
n--;
skipped++;
}
return skipped;
}
/**
* Return an estimate of the number of bytes remaining in the byte stream.
*
* @return the count of bytes that can be read without blocking (or returning EOF).
* @throws IOException if an error occurs (probably not possible)
*/
@Override
public int available() throws IOException {
// The cached entries are in bbuf; since encoding always creates at least one byte
// per character, we can add the two to get a better estimate (e.g. if bbuf is empty)
// Note that the previous implementation (2.4) could return zero even though there were
// encoded bytes still available.
return this.bbuf.remaining() + this.cbuf.remaining();
}
@Override
public void close() throws IOException {
}
/**
* {@inheritDoc}
*
* @param readlimit max read limit (ignored)
*/
@Override
public synchronized void mark(final int readlimit) {
this.mark_cbuf = this.cbuf.position();
this.mark_bbuf = this.bbuf.position();
this.cbuf.mark();
this.bbuf.mark();
// It would be nice to be able to use mark & reset on the cbuf and bbuf;
// however the bbuf is re-used so that won't work
}
@Override
public synchronized void reset() throws IOException {
/*
* This is not the most efficient implementation, as it re-encodes from the beginning. Since
* the bbuf is re-used, in general it's necessary to re-encode the data. It should be
* possible to apply some optimisations however: + use mark/reset on the cbuf and bbuf. This
* would only work if the buffer had not been (re)filled since the mark. The code would have
* to catch InvalidMarkException - does not seem possible to check if mark is valid
* otherwise. + Try saving the state of the cbuf before each fillBuffer; it might be
* possible to restart from there.
*/
if (this.mark_cbuf != NO_MARK) {
// if cbuf is at 0, we have not started reading anything, so skip re-encoding
if (this.cbuf.position() != 0) {
this.encoder.reset();
this.cbuf.rewind();
this.bbuf.rewind();
this.bbuf.limit(0); // rewind does not clear the buffer
while (this.cbuf.position() < this.mark_cbuf) {
this.bbuf.rewind(); // empty the buffer (we only refill when empty during normal
// processing)
this.bbuf.limit(0);
fillBuffer();
}
}
if (this.cbuf.position() != this.mark_cbuf) {
throw new IllegalStateException("Unexpected CharBuffer postion: actual=" + cbuf.position()
+ " expected=" + this.mark_cbuf);
}
this.bbuf.position(this.mark_bbuf);
this.mark_cbuf = NO_MARK;
this.mark_bbuf = NO_MARK;
}
}
@Override
public boolean markSupported() {
return true;
}
}