Mega Code Archive
Provides Closable semantics ordinarily missing in a java io CharArrayWriter
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/* Copyright (c) 2001-2009, The HSQL Development Group
* All rights reserved.
*
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*
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*
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*
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*
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import java.io.CharArrayReader;
import java.io.CharArrayWriter;
import java.io.IOException;
import java.io.Writer;
/**
* @todo - finer-grained synchronization to reduce average
* potential monitor contention
*/
/**
* Provides Closable semantics ordinarily missing in a
* {@link java.io.CharArrayWriter}. <p>
*
* Accumulates output in a character array that automatically grows as needed.<p>
*
* Data is retrieved using <tt>toCharArray()</tt>, <tt>toCharArrayReader()</tt>
* and <tt>toString()</tt>. <p>
*
* {@link #close() Closing} a <tt>ClosableCharArrayWriter</tt> prevents
* further write operations, but all other operations will succeed until after
* the first invocation of {@link #free() free()}.<p>
*
* Freeing a <tt>ClosableCharArrayWriter</tt> closes the writer and
* releases its internal buffer, preventing successful invocation of all
* operations, with the exception of <tt>size()<tt>, <tt>close()</tt>,
* <tt>isClosed()</tt>, <tt>free()</tt> and <tt>isFreed()</tt>. <p>
*
* This class is especially useful when an accumulating writer must be
* handed off to an extenal client under contract that the writer should
* exhibit true Closable behaviour, both in response to internally tracked
* events and to client invocation of the <tt>Writer.close()</tt> method.
*
* @author boucherb@users
* @version 1.8.x
* @since 1.8.x
*/
public class ClosableCharArrayWriter extends Writer {
/**
* Data buffer.
*/
protected char[] buf;
/**
* # of valid characters in buffer.
*/
protected int count;
/**
* Whether this writer is closed.
*/
protected boolean closed;
/**
* Whether this writer is freed.
*/
protected boolean freed;
/**
* Creates a new writer. <p>
*
* The buffer capacity is initially 32 characters, although its size
* automatically increases when necessary.
*/
public ClosableCharArrayWriter() {
this(32);
}
/**
* Creates a new writer with a buffer capacity of the specified
* <tt>size</tt>, in characters.
*
* @param size the initial size.
* @exception IllegalArgumentException if <tt>size</tt> is negative.
*/
public ClosableCharArrayWriter(int size) throws IllegalArgumentException {
if (size < 0) {
throw new IllegalArgumentException("Negative initial size: "
+ size); // NOI18N
}
buf = new char[size];
}
/**
* Writes the specified single character.
*
* @param c the single character to be written.
* @throws java.io.IOException if an I/O error occurs.
* In particular, an <tt>IOException</tt> may be thrown
* if this writer has been {@link #close() closed}.
*/
public synchronized void write(int c) throws IOException {
checkClosed();
int newcount = count + 1;
if (newcount > buf.length) {
buf = copyOf(buf, Math.max(buf.length << 1, newcount));
}
buf[count] = (char) c;
count = newcount;
}
/**
* Writes the designated portion of the designated character array <p>.
*
* @param c the source character sequence.
* @param off the start offset in the source character sequence.
* @param len the number of characters to write.
* @throws java.io.IOException if an I/O error occurs.
* In particular, an <tt>IOException</tt> may be thrown
* if this writer has been {@link #close() closed}.
*/
public synchronized void write(char c[], int off,
int len) throws IOException {
checkClosed();
if ((off < 0) || (off > c.length) || (len < 0)
|| ((off + len) > c.length) || ((off + len) < 0)) {
throw new IndexOutOfBoundsException();
} else if (len == 0) {
return;
}
int newcount = count + len;
if (newcount > buf.length) {
buf = copyOf(buf, Math.max(buf.length << 1, newcount));
}
System.arraycopy(c, off, buf, count, len);
count = newcount;
}
/**
* Efficiently writes the designated portion of the designated string. <p>
*
* The operation occurs as if by calling
* <tt>str.getChars(off, off + len, buf, count)</tt>. <p>
*
* @param str the string from which to write
* @param off the start offset in the string.
* @param len the number of characters to write.
* @throws java.io.IOException if an I/O error occurs.
* In particular, an <tt>IOException</tt> may be thrown
* if this writer has been {@link #close() closed}.
*/
public synchronized void write(String str, int off,
int len) throws IOException {
checkClosed();
int strlen = str.length();
if ((off < 0) || (off > strlen) || (len < 0) || ((off + len) > strlen)
|| ((off + len) < 0)) {
throw new IndexOutOfBoundsException();
} else if (len == 0) {
return;
}
int newcount = count + len;
if (newcount > buf.length) {
buf = copyOf(buf, Math.max(buf.length << 1, newcount));
}
str.getChars(off, off + len, buf, count);
count = newcount;
}
/**
* By default, does nothing. <p>
*
* @throws java.io.IOException if an I/O error occurs.
* In particular, an <tt>IOException</tt> may be thrown
* if this writer has been {@link #close() closed}.
*/
public void flush() throws IOException {
checkClosed();
}
/**
* Writes the complete contents of this writer's buffered data to the
* specified writer. <p>
*
* The operation occurs as if by calling <tt>out.write(buf, 0, count)</tt>.
*
* @param out the writer to which to write the data.
* @throws java.io.IOException if an I/O error occurs.
* In particular, an <tt>IOException</tt> may be thrown
* if this writer has been {@link #free() freed}.
*/
public synchronized void writeTo(Writer out) throws IOException {
checkFreed();
if (count > 0) {
out.write(buf, 0, count);
}
}
/**
* Returns the current capacity of this writer's data buffer.
*
* @return the current capacity (the length of the internal
* data array)
* @throws java.io.IOException if an I/O error occurs.
* In particular, an <tt>IOException</tt> may be thrown
* if this writer has been {@link #free() freed}.
*/
public synchronized int capacity() throws IOException {
checkFreed();
return buf.length;
}
/**
* Resets the <tt>count</tt> field of this writer to zero, so that all
* currently accumulated output is effectively discarded. Further write
* operations will reuse the allocated buffer space.
*
* @see #count
* @throws java.io.IOException if an I/O error occurs.
* In particular, an <tt>IOException</tt> may be thrown
* if this output stream has been {@link #close() closed}.
*/
public synchronized void reset() throws IOException {
checkClosed();
count = 0;
}
/**
* Attempts to reduce this writer's buffer capacity to its current size. <p>
*
* If the buffer is larger than necessary to hold its current sequence of
* characters, then it may be resized to become more space efficient.
* Calling this method may, but is not required to, affect the value
* returned by a subsequent call to the {@link #capacity()} method.
*/
public synchronized void trimToSize() throws IOException {
checkFreed();
if (buf.length > count) {
buf = copyOf(buf, count);
}
}
/**
* Creates a newly allocated character array. Its size is the current
* size of this writer and the valid contents of the buffer
* have been copied into it.
*
* @return the current contents of this writer, as a character array.
* @see #size()
* @throws java.io.IOException if an I/O error occurs.
* In particular, an <tt>IOException</tt> may be thrown
* if this writer has been {@link #free() freed}.
*/
public synchronized char[] toCharArray() throws IOException {
checkFreed();
return copyOf(buf, count);
}
/**
* Returns the current size of this writer's accumulated character data.
*
* @return the value of the <tt>count</tt> field, which is the number
* of valid characters accumulated in this writer.
* @see #count
* @throws java.io.IOException never
*/
public synchronized int size() throws IOException {
return count;
}
/**
* Sets the size of this writer's accumulated character data. <p>
*
* @param newSize the new size of this writer's accumulated data
* @throws ArrayIndexOutOfBoundsException if new size is negative
*/
public synchronized void setSize(int newSize) {
if (newSize < 0) {
throw new ArrayIndexOutOfBoundsException(newSize);
} else if (newSize > buf.length) {
buf = copyOf(buf, Math.max(buf.length << 1, newSize));
}
count = newSize;
}
/**
* Performs an effecient (zero-copy) conversion of the character data
* accumulated in this writer to a reader. <p>
*
* To ensure the integrity of the resulting reader, {@link #free()
* free} is invoked upon this writer as a side-effect.
*
* @return a reader representing this writer's accumulated
* character data
* @throws java.io.IOException if an I/O error occurs.
* In particular, an <tt>IOException</tt> may be thrown
* if this writer has been {@link #free() freed}.
*/
public synchronized CharArrayReader toCharArrayReader()
throws IOException {
checkFreed();
CharArrayReader reader = new CharArrayReader(buf, 0, count);
//System.out.println("toCharArrayReader::buf.length: " + buf.length);
free();
return reader;
}
/**
* Converts this writer's accumulated data into a string.
*
* @return String constructed from this writer's accumulated data
* @throws RuntimeException may be thrown if this writer has been
* {@link #free() freed}.
*/
public synchronized String toString() {
try {
checkFreed();
} catch (IOException ex) {
throw new RuntimeException(ex.toString());
}
return new String(buf, 0, count);
}
/**
* Closes this object for further writing. <p>
*
* Other operations may continue to succeed until after the first invocation
* of {@link #free() free()}. <p>
*
* @throws java.io.IOException if an I/O error occurs (default: never)
*/
public synchronized void close() throws IOException {
closed = true;
}
/**
* @return <tt>true</tt> if this writer is closed, else <tt>false</tt>
*/
public synchronized boolean isClosed() {
return closed;
}
/**
* Closes this object and releases the underlying buffer for
* garbage collection. <p>
*
* @throws java.io.IOException if an I/O error occurs while closing
* this writer (default: never).
*/
public synchronized void free() throws IOException {
closed = true;
freed = true;
buf = null;
count = 0;
}
/**
* @return <tt>true</tt> if this writer is freed; else <tt>false</tt>.
*/
public synchronized boolean isFreed() {
return freed;
}
/**
* @throws java.io.IOException if this writer is closed.
*/
protected synchronized void checkClosed() throws IOException {
if (closed) {
throw new IOException("writer is closed."); // NOI18N
}
}
/**
* @throws java.io.IOException if this writer is freed.
*/
protected synchronized void checkFreed() throws IOException {
if (freed) {
throw new IOException("write buffer is freed."); // NOI18N
}
}
/**
* Retrieves a copy of <tt>original</tt> with the given
* <tt>newLength</tt>. <p>
*
* @param original the object to copy
* @param newLength the length of the copy
* @return copy of <tt>original</tt> with the given <tt>newLength</tt>
*/
protected char[] copyOf(char[] original, int newLength) {
char[] copy = new char[newLength];
System.arraycopy(original, 0, copy, 0,
Math.min(original.length, newLength));
return copy;
}
}
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