Initial revision

From-SVN: r102074

libjava/classpath/java/util/zip/CheckedInputStream.java

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+/* CheckedInputStream.java - Compute checksum of data being read
+   Copyright (C) 1999, 2000, 2004  Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+ 
+GNU Classpath is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library.  Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module.  An independent module is a module which is not derived from
+or based on this library.  If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so.  If you do not wish to do so, delete this
+exception statement from your version. */
+
+
+package java.util.zip;
+
+import java.io.FilterInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+
+/* Written using on-line Java Platform 1.2 API Specification
+ * and JCL book.
+ * Believed complete and correct.
+ */
+
+/**
+ * InputStream that computes a checksum of the data being read using a
+ * supplied Checksum object.
+ *
+ * @see Checksum
+ *
+ * @author Tom Tromey
+ * @date May 17, 1999
+ */
+public class CheckedInputStream extends FilterInputStream
+{
+  /**
+   * Creates a new CheckInputStream on top of the supplied OutputStream
+   * using the supplied Checksum.
+   */
+  public CheckedInputStream (InputStream in, Checksum sum)
+  {
+    super (in);
+    this.sum = sum;
+  }
+
+  /**
+   * Returns the Checksum object used. To get the data checksum computed so
+   * far call <code>getChecksum.getValue()</code>.
+   */
+  public Checksum getChecksum ()
+  {
+    return sum;
+  }
+
+  /**
+   * Reads one byte, updates the checksum and returns the read byte
+   * (or -1 when the end of file was reached).
+   */
+  public int read () throws IOException
+  {
+    int x = in.read();
+    if (x != -1)
+      sum.update(x);
+    return x;
+  }
+
+  /**
+   * Reads at most len bytes in the supplied buffer and updates the checksum
+   * with it. Returns the number of bytes actually read or -1 when the end
+   * of file was reached.
+   */
+  public int read (byte[] buf, int off, int len) throws IOException
+  {
+    int r = in.read(buf, off, len);
+    if (r != -1)
+      sum.update(buf, off, r);
+    return r;
+  }
+
+  /**
+   * Skips n bytes by reading them in a temporary buffer and updating the
+   * the checksum with that buffer. Returns the actual number of bytes skiped
+   * which can be less then requested when the end of file is reached.
+   */
+  public long skip (long n) throws IOException
+  {
+    if (n == 0)
+      return 0;
+
+    int min = (int) Math.min(n, 1024);
+    byte[] buf = new byte[min];
+
+    long s = 0;
+    while (n > 0)
+      {
+	int r = in.read(buf, 0, min);
+	if (r == -1)
+	  break;
+	n -= r;
+	s += r;
+	min = (int) Math.min(n, 1024);
+	sum.update(buf, 0, r);
+      }
+
+    return s;
+  }
+
+  /** The checksum object. */
+  private Checksum sum;
+}