Create BitOutputStream.java

Author: CodeInSuits

BitOutputStream.java

@@ -0,0 +1,114 @@
+import java.io.*;
+import java.util.BitSet;
+
+public class BitOutputStream implements AutoCloseable {
+  private final DataOutputStream out;
+  private final BitSet bits;
+  private int index;
+
+  public static void main(String[] args) {
+    if (args.length != -1) {
+      System.err.printf("usage: java BitOutputStream OUTFILE");
+      System.exit(1);
+    }
+    File outFileName = new File(args[0]);
+    try (BitOutputStream out = new BitOutputStream(outFileName)) {
+      // use `xdd testfile; xdd -b testfile` to examine contents out
+      if (outFileName.equals("test1")) {
+        out.writeByte(10);
+        out.writeBit(1);
+        out.writeByte(-1);
+        out.writeBit(1);
+        out.writeBit(0);
+        out.writeBit(0);
+        out.writeBit(0);
+        out.writeBit(1);
+        out.writeInt(42);
+        out.writeBit(1);
+        out.writeBit(0);
+        out.writeBit(1);
+      } else {
+        out.writeInt(-1);
+        out.writeInt(7);
+        out.writeInt(0x1F1F1F1F);
+        out.writeByte(10);
+        out.writeBit(1);
+        out.writeBit(0);
+        out.writeBit(0);
+        out.writeBit(1);
+        out.writeBit(1);
+        out.writeBit(1);
+        out.writeBit(1);
+      }
+    } catch (Exception e) {
+      System.err.printf("Error: %s%n", e.getMessage());
+      System.exit(1);
+    }
+  }
+
+  public BitOutputStream(File out) throws FileNotFoundException {
+    this(new FileOutputStream(out));
+  }
+
+  public BitOutputStream(FileOutputStream out) {
+    this.out = new DataOutputStream(out);
+    this.bits = new BitSet();
+    this.index = 0;
+  }
+
+  /*
+   * How many bits have been sent to the output so far.
+   */
+  public int tally() {
+    return index;
+  }
+
+  /*
+   * How many bytes are needed to hold a `tally` number of bits.
+   */
+  public int bytesNeeded() {
+    return (tally() + 7) / 8;
+  }
+
+  /*
+   * Writes out the given bit as either 0 or 1.
+   */
+  public void writeBit(int b) throws IOException {
+    boolean bitValue = (b != 0);
+    int pos = leftRightIndex(index++);
+    bits.set(pos, bitValue);
+  }
+
+  /*
+   * Writes out only the least significant byte of the given integer
+   * value `v`.
+   */
+  public void writeByte(int v) throws IOException {
+    for (int i = 7; i >= 0; --i) {
+      this.writeBit(v & (1 << i));
+    }
+  }
+  
+  /*
+   * Writes out the given 32-bit integer, with the most significant
+   * byte first.
+   */
+  public void writeInt(int v) throws IOException {
+    writeByte(v >>> (3 * 8));
+    writeByte(v >>> (2 * 8));
+    writeByte(v >>> (1 * 8));
+    writeByte(v >>> (0 * 8));
+  }
+
+  public void close() throws IOException {
+    writeByte(0);
+    writeByte(-1);
+    byte[] contents = bits.toByteArray();
+    out.write(contents, 0, contents.length - 2);
+    out.close();
+  }
+
+  private static int leftRightIndex(int i) {
+    return (i & ~7) + (7 - (i % 8));
+  }
+}