bit_partition function added - its like quicksort, but different

ypsu.cpp

@@ -144,6 +144,33 @@ void twopass(uint32_t *a, int n) {
 //     --index
 // különben
 //     ++pivot_index
+/**
+ * Divides array into two partitions by its topmost bit.
+ * - Similar to quicksort partitioning, but changed accordingly.
+ * - MSB 0 bit values will come first partition.
+ * - The return value tells partition boundary.
+ *
+ * @param a The array to partition and occurence count.
+ * @param n The length of the array.
+ */
+static inline uint32_t bit_partition(uint32_t *a, uint32_t n) noexcept {
+	uint32_t i = -1;
+	uint32_t j = n;
+
+	while(true) {
+		// Move past well-placed ones
+		do ++i; while (!(a[i] & 0x80));
+		do --j; while (a[j] & 0x80);
+
+		// If the indices crossed, return
+		if(i >= j) return j;
+
+		// Swap badly placed
+		uint32_t tmp = a[i];
+		a[i] = a[j];
+		a[j] = tmp;
+	}
+}
 template<int j>
 static inline uint32_t morgrab(uint32_t elem) noexcept {
 	return (elem >> (8 * j)) & 0xff;