split xor8 code from hash.c to independent program

hash/hash_xor8.c

@@ -0,0 +1,50 @@
+/**
+ * @addtogroup hash Hash algorithms
+ * @{
+ * @file hash_xor8.c
+ * @author [Christian Bender](https://github.com/christianbender)
+ * @brief 8-bit [XOR hash](https://en.wikipedia.org/wiki/XOR_cipher) algorithm
+ * for ASCII characters
+ */
+#include <assert.h>
+#include <inttypes.h>
+#include <stdio.h>
+
+/**
+ * @brief 8-bit XOR algorithm implementation
+ *
+ * @param s NULL terminated ASCII string to hash
+ * @return 8-bit hash result
+ */
+uint8_t xor8(const char* s)
+{
+    uint8_t hash = 0;
+    size_t i = 0;
+    while (s[i] != '\0')
+    {
+        hash = (hash + s[i]) & 0xff;
+        i++;
+    }
+    return (((hash ^ 0xff) + 1) & 0xff);
+}
+
+/**
+ * @brief Test function for ::xor8
+ */
+void test_xor8()
+{
+    assert(xor8("Hello World") == 228);
+    assert(xor8("Hello World!") == 195);
+    assert(xor8("Hello world") == 196);
+    assert(xor8("Hello world!") == 163);
+    printf("Tests passed\n");
+}
+
+/** @} */
+
+/** Main function */
+int main()
+{
+    test_xor8();
+    return 0;
+}