[Feature] Support for importing from Uint8List (#12)

* [Feature] Support for importing from Uint8List

* [Feature] Support for BitArray.fromString

* [Code Review] Changes according to code review comments

Author: yanivshaked

lib/src/bit_array.dart

@@ -28,6 +28,35 @@ class BitArray extends BitSet {
     return BitArray._(data);
   }
 
+  /// Creates a bit array using a Uint8List.
+  factory BitArray.fromUint8List(Uint8List list) {
+    if (list.lengthInBytes % 4 != 0) {
+      throw FormatException('Uint8List length must be a multiplication of 4');
+    }
+    final data =
+        list.buffer.asUint32List(list.offsetInBytes, list.lengthInBytes >> 2);
+    return BitArray._(data);
+  }
+
+  /// Create a bit array from a binary string.
+  factory BitArray.parseBinary(String bitString) {
+    var data = Uint32List((bitString.length + 31) >> 5);
+    var bitIndex = 0;
+    for (var i = bitString.length - 1; i >= 0; i--) {
+      if (bitString[i] == '0') {
+        bitIndex++;
+        // Nothing to do
+      } else if (bitString[i] == '1') {
+        var wordIndex = (bitIndex) >> 5;
+        data[wordIndex] |= 1 << (bitIndex % 32);
+        bitIndex++;
+      } else {
+        throw FormatException('Binary string should consist of 0s and 1s only');
+      }
+    }
+    return BitArray._(data);
+  }
+
   /// The value of the bit with the specified [index].
   @override
   bool operator [](int index) {

test/bit_array_test.dart

@@ -1,3 +1,5 @@
+import 'dart:typed_data';
+
 import 'package:test/test.dart';
 
 import 'package:bit_array/bit_array.dart';
@@ -81,6 +83,35 @@ void main() {
         expect(deccumulator[i], accumulator[i]);
       }
     });
+
+    test('fromUint8list', () {
+      var list = Uint8List.fromList(<int>[0xAA, 0x55, 0x1b, 0x1a]);
+      var bitArray = BitArray.fromUint8List(list);
+
+      for (int w = 0; w < 2; w++) {
+        var word = 0;
+        for (int b = 7; b >= 0; b--) {
+          word <<= 1;
+          word |= (bitArray[b + w * 8] ? 1 : 0);
+        }
+        expect(word, list[w]);
+      }
+    });
+
+    test('fromString', () {
+      void testBitString(String bitString) {
+        var reversedBitString = bitString.split('').reversed.join();
+        var bitArray = BitArray.parseBinary(bitString);
+        for (int i = 0; i < bitString.length; i++) {
+          expect(bitArray[i], reversedBitString[i] == '1');
+        }
+      }
+
+      testBitString('111010');
+      testBitString('101010010101001001000100101110');
+      testBitString('10101001011101110101110011101010110101011111110110');
+    });
+
     test('array ops', () {
       final oooo = BitArray(32);
       expect(oooo.toBinaryString().substring(0, 4), '0000');