Initial commit

common/rfb/adler32.h

@@ -0,0 +1,52 @@
+#include <stdint.h>
+
+// contributed by Dmitry Artamonov
+// this is *deterministic*
+class Adler32 {
+	uint32_t sum1, sum2;
+	int len;
+
+	enum {
+		Base = 65521
+	};
+
+public:
+	uint32_t hash;
+
+	Adler32(int window) : sum1(1), sum2(0), len(window), hash(0) {}
+
+	void eat(const uint8_t inchar) {
+		sum1 = (sum1 + inchar) % Base;
+		sum2 = (sum2 + sum1) % Base;
+
+		hash = (sum2 << 16) | sum1;
+	}
+
+	void reset() {
+	  sum1 = 1;
+	  sum2 = 0;
+	  hash = 0;
+	}
+
+	void update(const uint8_t outchar, const uint8_t inchar) {
+		int sum2 = (hash >> 16) & 0xffff;
+		int sum1 = hash & 0xffff;
+
+		sum1 += inchar - outchar;
+		if (sum1 >= Base)
+		{
+			sum1 -= Base;
+		}
+		else if (sum1 < 0)
+		{
+			sum1 += Base;
+		}
+
+		sum2 = ((int)(sum2 - len * outchar + sum1 - 1) % (int)Base);
+		if (sum2 < 0)
+		{
+			sum2 += Base;
+		}
+		hash = (sum2 << 16) | sum1;
+	}
+};