Reader.java: Merge docs from classpath.

	* java/io/Reader.java: Merge docs from classpath.
	(skip): Synchronize on `lock'.
	* java/io/FileReader.java: Import correct implementation from
	classpath.
	* java/io/StringReader.java: Merge docs from classpath.
	(ready): Throw IOException if stream is closed.

From-SVN: r37143

1 files changed, 171 insertions, 17 deletions

diff --git a/libjava/java/io/Reader.java b/libjava/java/io/Reader.java
index c8e8f29..e8329d6 100644
--- a/libjava/java/io/Reader.java
+++ b/libjava/java/io/Reader.java
@@ -1,4 +1,4 @@
-/* Copyright (C) 1998, 1999  Free Software Foundation
+/* Copyright (C) 1998, 1999, 2000  Free Software Foundation
 
    This file is part of libgcj.
 
@@ -7,38 +7,115 @@ Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
 details.  */
  
 package java.io;
-
-/**
- * @author Per Bothner <bothner@cygnus.com>
- * @date April 21, 1998.  
- */
+ 
 /* Written using "Java Class Libraries", 2nd edition, plus online
  * API docs for JDK 1.2 beta from http://www.javasoft.com.
  * Status:  Believed complete and correct.
  */
 
+/**
+ * This abstract class forms the base of the hierarchy of classes that read
+ * input as a stream of characters.  It provides a common set of methods for
+ * reading characters from streams.  Subclasses implement and extend these
+ * methods to read characters from a particular input source such as a file
+ * or network connection.
+ *
+ * @author Per Bothner <bothner@cygnus.com>
+ * @date April 21, 1998.  
+ * @author Aaron M. Renn (arenn@urbanophile.com) 
+ */
 public abstract class Reader
 {
+  /**
+   * This is the <code>Object</code> used for synchronizing critical code
+   * sections.  Subclasses should use this variable instead of a 
+   * synchronized method or an explicit synchronization on <code>this</code>
+   */
   protected Object lock;
-
+  
+  /**
+    * Unitializes a <code>Reader</code> that will use the object
+    * itself for synchronization of critical code sections.
+    */
   protected Reader()
   {
     this.lock = this;
   }
 
+  /**
+    * Initializes a <code>Reader</code> that will use the specified
+    * <code>Object</code> for synchronization of critical code sections.
+    *
+    * @param lock The <code>Object</code> to use for synchronization
+    */
   protected Reader(Object lock)
   {
     this.lock = lock;
   }
 
-  abstract public int read(char buf[], int offset, int count)
+  /**
+   * Read chars from a stream and stores them into a caller
+   * supplied buffer.  It starts storing the data at index <code>offset</code> 
+   * into the buffer and attempts to read <code>len</code> chars.  This method 
+   * can return before reading the number of chars requested.  The actual 
+   * number of chars read is returned as an int.  A -1 is returned to indicate 
+   * the end of the stream.
+   * <p>
+   * This method will block until some data can be read.
+   * <p>
+   * This method operates by calling the single char <code>read()</code> method
+   * in a loop until the desired number of chars are read.  The read loop
+   * stops short if the end of the stream is encountered or if an IOException
+   * is encountered on any read operation except the first.  If the first
+   * attempt to read a chars fails, the IOException is allowed to propagate
+   * upward.  And subsequent IOException is caught and treated identically
+   * to an end of stream condition.  Subclasses can (and should if possible)
+   * override this method to provide a more efficient implementation.
+   *
+   * @param buf The array into which the chars read should be stored
+   * @param offset The offset into the array to start storing chars
+   * @param len The requested number of chars to read
+   *
+   * @return The actual number of chars read, or -1 if end of stream.
+   *
+   * @exception IOException If an error occurs.
+   */
+  public abstract int read(char buf[], int offset, int count)
     throws IOException;
-
+    
+  /**
+   * Reads chars from a stream and stores them into a caller
+   * supplied buffer.  This method attempts to completely fill the buffer,
+   * but can return before doing so.  The actual number of chars read is
+   * returned as an int.  A -1 is returned to indicate the end of the stream.
+   * <p>
+   * This method will block until some data can be read.
+   * <p>
+   * This method operates by calling an overloaded read method like so:
+   * <code>read(buf, 0, buf.length)</code>
+   *
+   * @param buf The buffer into which the chars read will be stored.
+   *
+   * @return The number of chars read or -1 if end of stream.
+   *
+   * @exception IOException If an error occurs.
+   */
   public int read(char buf[]) throws IOException
   {
     return read(buf, 0, buf.length);
   }
 
+  /**
+   * Reads an char from the input stream and returns it
+   * as an int in the range of 0-65535.  This method also will return -1 if
+   * the end of the stream has been reached.
+   * <p>
+   * This method will block until the char can be read.
+   *
+   * @return The char read or -1 if end of stream
+   *
+   * @exception IOException If an error occurs
+   */
   public int read() throws IOException
   {
     char[] buf = new char[1];
@@ -46,28 +123,102 @@ public abstract class Reader
     return count > 0 ? buf[0] : -1;
   }
 
-  abstract public void close() throws IOException;
+  /**
+   * Closes the stream.  Any futher attempts to read from the
+   * stream may generate an <code>IOException</code>.
+   *
+   * @exception IOException If an error occurs
+   */
+  public abstract void close() throws IOException;
 
+  /**
+   * Returns a boolean that indicates whether the mark/reset
+   * methods are supported in this class.  Those methods can be used to
+   * remember a specific point in the stream and reset the stream to that
+   * point.
+   * <p>
+   * This method always returns <code>false</code> in this class, but
+   * subclasses can override this method to return <code>true</code> if they 
+   * support mark/reset functionality.
+   *
+   * @return <code>true</code> if mark/reset functionality is supported, 
+   *         <code>false</code> otherwise
+   *
+   */
   public boolean markSupported()
   {
     return false;
   }
 
+  /**
+    * Marks a position in the input to which the stream can be
+    * "reset" by calling the <code>reset()</code> method.  The parameter
+    * <code>readlimit</code> is the number of chars that can be read from the 
+    * stream after setting the mark before the mark becomes invalid.  For
+    * example, if <code>mark()</code> is called with a read limit of 10, then 
+    * when 11 chars of data are read from the stream before the 
+    * <code>reset()</code> method is called, then the mark is invalid and the 
+    * stream object instance is not required to remember the mark.
+    *
+    * @param readlimit The number of chars that can be read before the mark 
+    *        becomes invalid
+    *
+    * @exception IOException If an error occurs such as mark not being 
+    *            supported for this class
+    */
   public void mark(int readLimit) throws IOException
   {
     throw new IOException("mark not supported");
   }
 
+  /**
+    * Resets a stream to the point where the <code>mark()</code> 
+    * method was called.  Any chars that were read after the mark point was 
+    * set will be re-read during subsequent reads.
+    * <p>
+    * This method always throws an IOException in this class, but subclasses
+    * can override this method if they provide mark/reset functionality.
+    *
+    * @exception IOException Always thrown for this class
+    */
   public void reset() throws IOException
   {
     throw new IOException("reset not supported");
   }
 
+  /**
+    * Determines whether or not this stream is ready to be
+    * read.  If it returns <code>false</code> the stream may block if a
+    * read is attempted, but it is not guaranteed to do so.
+    * <p>
+    * This method always returns <code>false</code> in this class
+    *
+    * @return <code>true</code> if the stream is ready to be read, <code>false</code> otherwise.
+    *
+    * @exception IOException If an error occurs
+    */
   public boolean ready() throws IOException
   {
     return false;
   }
 
+  /**
+    * Skips the specified number of chars in the stream.  It
+    * returns the actual number of chars skipped, which may be less than the
+    * requested amount.
+    * <p>
+    * This method reads and discards chars into a 256 char array until the
+    * specified number of chars were skipped or until either the end of stream
+    * is reached or a read attempt returns a short count.  Subclasses can
+    * override this method to provide a more efficient implementation where
+    * one exists.
+    *
+    * @param num_chars The requested number of chars to skip
+    *
+    * @return The actual number of chars skipped.
+    *
+    * @exception IOException If an error occurs
+    */
   public long skip(long count) throws IOException
   {
     if (count <= 0)
@@ -75,13 +226,16 @@ public abstract class Reader
     int bsize = count > 1024 ? 1024 : (int) count;
     char[] buffer = new char[bsize];
     long todo = count;
-    while (todo > 0)
-      {
-	int skipped = read(buffer, 0, bsize > todo ? (int) todo : bsize);
-	if (skipped <= 0)
-	  break;
-	todo -= skipped;
-      }
+    synchronized (lock)
+    {
+      while (todo > 0)
+	{
+	  int skipped = read(buffer, 0, bsize > todo ? (int) todo : bsize);
+	  if (skipped <= 0)
+	    break;
+	  todo -= skipped;
+	}
+    }
     return count - todo;
   }
 }