init

p3/BitOutputStream.java

@@ -0,0 +1,74 @@
+// The BitOutputStream and BitInputStream classes provide the ability to
+// write and read individual bits to a file in a compact form.  One major
+// limitation of this approach is that the resulting file will always have
+// a number of bits that is a multiple of 8.  In effect, whatever bits are
+// output to the file are padded at the end with 0's to make the total
+// number of bits a multiple of 8.
+
+import java.io.*;
+import java.util.*;
+
+@SuppressWarnings("deprecation")
+public class BitOutputStream {
+	private PrintStream output;
+    private List<Integer> buffer;
+	private int currentByte; // a buffer used to build up next set of digits
+	private int numBits; // how many digits are currently in the buffer
+	private boolean debug; // set to true to write ASCII 0s and 1s rather than
+							// bits
+
+	private static final int BYTE_SIZE = 8; // digits per byte
+
+	// Creates a BitOutputStream sending output to the given stream. If debug
+	// is set to true, bits are printed as ASCII 0s and 1s.
+	public BitOutputStream(PrintStream output, boolean debug) {
+        this.buffer = new ArrayList<Integer>();
+		this.output = output;
+		this.debug = debug;
+	}
+
+	// Writes given bit to output
+	public void write(int bit) {
+		if (this.debug) {
+			System.out.print(bit);
+		} 
+        if (bit < 0 || bit > 1) {
+            throw new IllegalArgumentException("Illegal bit: " + bit);
+        }
+        this.currentByte += bit << this.numBits;
+        this.numBits++;
+        if (this.numBits == BYTE_SIZE) {
+            this.buffer.add(this.currentByte);
+            this.numBits = 0;
+            this.currentByte = 0;
+        }
+	}
+
+	// post: output is closed
+	public void close() {
+        int remaining = BYTE_SIZE - this.numBits;
+
+        if (remaining == 8) {
+            remaining = 0;
+        } 
+
+        /* Flush the last byte (if there is one) */
+        if (remaining > 0) {
+            this.buffer.add(this.currentByte);
+        }
+
+        /* Now that we've received all the output, prepend it with the number
+         * of missing bits from the end.
+         */
+		this.output.write(remaining);
+        for (int b : this.buffer) {
+            this.output.write(b);
+        }
+		this.output.close();
+	}
+
+	// included to ensure that the stream is closed
+	protected void finalize() {
+		this.close();
+	}
+}