DirectWriter.java from DrJava at Krugle

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/*BEGIN_COPYRIGHT_BLOCK*

PLT Utilities BSD License

Copyright (c) 2007 JavaPLT group at Rice University
All rights reserved.

Developed by:   Java Programming Languages Team
                Rice University
                http://www.cs.rice.edu/~javaplt/

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      and the following disclaimer.
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package edu.rice.cs.plt.io;

import java.io.*;

/**
 * A {@code Writer} that supports writing directly from a {@code Reader}.  This class
 * provides default implementations defined in terms of {@code Reader} and {@code Writer}
 * methods.  Subclasses can override (at least) {@link #writeAll(Reader, char[])} and
 * {@link #write(Reader, int, char[])} to provide better implementations (by, for example,
 * not invoking {@link Writer#write(char[])}).
 * 
 * @see DirectOutputStream
 * @see DirectReader
 * @see DirectInputStream
 */
public abstract class DirectWriter extends Writer {
  
  protected static final int DEFAULT_BUFFER_SIZE = 1024;

  /**
   * Write some number of characters, using the provided {@code Reader} as input.  Fewer characters
   * may be written if the reader has fewer available.  The default implementation 
   * invokes {@link #write(Reader, int, int)} with the minimum of {@code chars} and 
   * {@link #DEFAULT_BUFFER_SIZE}.  Subclasses that do not rely on a buffer in 
   * {@link #write(Reader, int, char[])} should override this method.
   * 
   * @param r  A reader to be read from
   * @param chars  The number of characters to write
   * @return  {@code -1} if the reader is at the end of file; otherwise, the number of characters written
   * @throws IOException  If an error occurs during reading or writing
   */
  public int write(Reader r, int chars) throws IOException {
    return write(r, chars, (chars < DEFAULT_BUFFER_SIZE) ? chars : DEFAULT_BUFFER_SIZE);
  }
  
  /**
   * Write some number of characters, using the provided {@code Reader} as input.  Fewer characters
   * may be written if the reader has fewer available.  The default implementation 
   * invokes {@link #write(Reader, int, char[])} with a newly-allocated array of the given size.  
   * Subclasses that do not rely on a buffer in {@link #write(Reader, int, char[])} should override 
   * this method.
   * 
   * @param r  A reader to be read from
   * @param chars  The number of characters to write
   * @param bufferSize  The size of buffer to use (if necessary).  Smaller values may reduce the amount of
   *                    memory required; larger values may increase performance on large readers
   * @return  {@code -1} if the reader is at the end of file; otherwise, the number of characters written
   * @throws IOException  If an error occurs during reading or writing
   * @throws IllegalArgumentException  If {@code bufferSize <= 0}
   */
  public int write(Reader r, int chars, int bufferSize) throws IOException {
    return write(r, chars, new char[bufferSize]);
  }
  
  /**
   * Write some number of characters, using the provided {@code Reader} as input.  Fewer characters
   * may be written if the reader has fewer available.  The given buffer is useful in repeated 
   * {@code write} invocations to avoid unnecessary memory allocation.  The default implementation 
   * repeatedly fills the given buffer via a {@link Reader#read(char[], int, int)} operation, then 
   * writes it via {@link Writer#write(char[], int, int)}.  Subclasses that do not require an external 
   * buffer should override this method.
   * 
   * @param r  A reader to be read from
   * @param chars  The number of characters to write
   * @param buffer  A buffer used to copy characters from the reader to this writer.  Note that this is only
   *                used to avoid unnecessary memory allocation.  No assumptions are made about the buffer's
   *                contents (which may be overwritten), and no assumptions should be made about the contents
   *                of the buffer after the method invocation.
   * @return  {@code -1} if the reader is at the end of file; otherwise, the number of characters written
   * @throws IOException  If an error occurs during reading or writing
   * @throws IllegalArgumentException  If {@code buffer} has size {@code 0}
   */
  public int write(Reader r, int chars, char[] buffer) throws IOException {
    return IOUtil.doWriteFromReader(r, this, chars, buffer);
  }
  
  /**
   * Write the full contents of the given {@code Reader} to this writer.  The method will block 
   * until an end-of-file is reached.  The default implementation invokes 
   * {@link #writeAll(Reader, int)} with {@link #DEFAULT_BUFFER_SIZE}.  Subclasses that know the 
   * size of this reader's remaining contents, or that do not rely on a buffer in 
   * {@link #writeAll(Reader, char[])}, should override this method.
   * 
   * @param r  A reader to be read from
   * @return  {@code -1} if the reader is at the end of file; otherwise, the number of characters written 
   *          (or, if the number is too large, {@code Integer.MAX_VALUE})
   * @throws IOException  If an error occurs during reading or writing
   */
  public int writeAll(Reader r) throws IOException { 
    return writeAll(r, DEFAULT_BUFFER_SIZE);
  }
  
  /**
   * Write the full contents of the given {@code Reader} to this writer.  The method will block 
   * until an end-of-file is reached.  The default implementation invokes 
   * {@link #writeAll(Reader, char[])} with a newly-allocated array of the given size.  Subclasses 
   * that do not rely on a buffer in {@link #writeAll(Reader, char[])} should override this method.
   * 
   * @param r  A reader to be read from
   * @param bufferSize  The size of buffer to use (if necessary).  Smaller values may reduce the amount of
   *                    memory required; larger values may increase performance on large readers
   * @return  {@code -1} if the reader is at the end of file; otherwise, the number of characters written 
   *          (or, if the number is too large, {@code Integer.MAX_VALUE})
   * @throws IOException  If an error occurs during reading or writing
   * @throws IllegalArgumentException  If {@code bufferSize <= 0}
   */
  public int writeAll(Reader r, int bufferSize) throws IOException { 
    return writeAll(r, new char[bufferSize]);
  }

  /**
   * Write the full contents of the given {@code Reader} to this writer.  The given buffer is useful 
   * in repeated {@code writeAll} invocations to avoid unnecessary memory allocation.  The method will 
   * block until an end-of-file is reached.  The default implementation repeatedly fills the given buffer 
   * via a {@link Reader#read(char[])} operation, then writes it via {@link Writer#write(char[])}.  
   * Subclasses that do not require an external buffer should override this method.
   * 
   * @param r  A reader to be read from
   * @param buffer  A buffer used to copy characters from the reader to this writer.  Note that this is only
   *                used to avoid unnecessary memory allocation.  No assumptions are made about the buffer's
   *                contents (which may be overwritten), and no assumptions should be made about the contents
   *                of the buffer after the method invocation.
   * @return  {@code -1} if the reader is at the end of file; otherwise, the number of characters written 
   *          (or, if the number is too large, {@code Integer.MAX_VALUE})
   * @throws IOException  If an error occurs during reading or writing
   * @throws IllegalArgumentException  If {@code buffer} has size {@code 0}
   */
  public int writeAll(Reader r, char[] buffer) throws IOException {
    return IOUtil.doCopyReader(r, this, buffer);
  }
  
}
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