add hw2

node_modules/unbzip2-stream/lib/bit_iterator.js

@@ -0,0 +1,39 @@
+var BITMASK = [0, 0x01, 0x03, 0x07, 0x0F, 0x1F, 0x3F, 0x7F, 0xFF];
+
+// returns a function that reads bits.
+// takes a buffer iterator as input
+module.exports = function bitIterator(nextBuffer) {
+    var bit = 0, byte = 0;
+    var bytes = nextBuffer();
+    var f = function(n) {
+        if (n === null && bit != 0) {  // align to byte boundary
+            bit = 0
+            byte++;
+            return;
+        }
+        var result = 0;
+        while(n > 0) {
+            if (byte >= bytes.length) {
+                byte = 0;
+                bytes = nextBuffer();
+            }
+            var left = 8 - bit;
+            if (bit === 0 && n > 0)
+                f.bytesRead++;
+            if (n >= left) {
+                result <<= left;
+                result |= (BITMASK[left] & bytes[byte++]);
+                bit = 0;
+                n -= left;
+            } else {
+                result <<= n;
+                result |= ((bytes[byte] & (BITMASK[n] << (8 - n - bit))) >> (8 - n - bit));
+                bit += n;
+                n = 0;
+            }
+        }
+        return result;
+    };
+    f.bytesRead = 0;
+    return f;
+};