QuickXor implementation

src/qxor.d

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+import std.algorithm;
+import std.digest.digest;
+
+// implementation of the QuickXorHash algorithm in D
+// https://github.com/OneDrive/onedrive-api-docs/blob/master/snippets/quickxorhash.md
+struct QuickXor
+{
+	private immutable int widthInBits = 160;
+	private immutable size_t lengthInBytes = (widthInBits - 1) / 8 + 1;
+	private immutable size_t lengthInQWords = (widthInBits - 1) / 64 + 1;
+	private immutable int bitsInLastCell = widthInBits % 64; // 32
+	private immutable int shift = 11;
+
+	private ulong[lengthInQWords] _data;
+	private ulong _lengthSoFar;
+	private int _shiftSoFar;
+
+	nothrow @safe void put(scope const(ubyte)[] array...)
+    {
+		int vectorArrayIndex = _shiftSoFar / 64;
+		int vectorOffset = _shiftSoFar % 64;
+        size_t iterations = min(array.length, widthInBits);
+
+		for (size_t i = 0; i < iterations; i++) {
+			bool isLastCell = vectorArrayIndex == _data.length - 1;
+			int bitsInVectorCell = isLastCell ? bitsInLastCell : 64;
+
+			if (vectorOffset <= bitsInVectorCell - 8) {
+				 for (size_t j = i; j < array.length; j += widthInBits) {
+					_data[vectorArrayIndex] ^= cast(ulong) array[j] << vectorOffset;
+				 }
+			} else {
+				int index1 = vectorArrayIndex;
+				int index2 = isLastCell ? 0 : (vectorArrayIndex + 1);
+				byte low = cast(byte) (bitsInVectorCell - vectorOffset);
+
+				byte xoredByte = 0;
+				for (int j = i; j < array.length; j += widthInBits) {
+					xoredByte ^= array[j];
+				}
+
+				_data[index1] ^= cast(ulong) xoredByte << vectorOffset;
+				_data[index2] ^= cast(ulong) xoredByte >> low;
+			}
+
+			vectorOffset += shift;
+			if (vectorOffset >= bitsInVectorCell) {
+				vectorArrayIndex = isLastCell ? 0 : vectorArrayIndex + 1;
+				vectorOffset -= bitsInVectorCell;
+			}
+		}
+
+		_shiftSoFar += (_shiftSoFar + shift * array.length) % widthInBits;
+		_lengthSoFar += array.length;
+
+	}
+
+	nothrow @safe void start()
+	{
+		_data = _data.init;
+		_shiftSoFar = 0;
+		_lengthSoFar = 0;
+	}
+
+	nothrow @trusted ubyte[lengthInBytes] finish()
+	{
+		ubyte[lengthInBytes] tmp;
+		tmp[0 .. lengthInBytes] = (cast(ubyte*) _data)[0 .. lengthInBytes];
+		for (size_t i = 0; i < 8; i++) {
+            tmp[lengthInBytes - 8 + i] ^= (cast(ubyte*) &_lengthSoFar)[i];
+        }
+		return tmp;
+	}
+}
+
+unittest
+{
+	assert(isDigest!QuickXor);
+}
+
+unittest
+{
+	QuickXor qxor;
+	qxor.put(cast(ubyte[]) "The quick brown fox jumps over the lazy dog");
+	assert(qxor.finish().toHexString() == "6CC4A56F2B26C492FA4BBE57C1F31C4193A972BE");
+}
+
+alias QuickXorDigest = WrapperDigest!(QuickXor);