api-v3: First draft

[src/app-framework-binder.git] / src / pearson.c

diff --git a/src/pearson.c b/src/pearson.c
new file mode 100644 (file)
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--- /dev/null
+++ b/src/pearson.c
@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2018 "IoT.bzh"
+ * Author: José Bollo <jose.bollo@iot.bzh>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <stdint.h>
+
+/*
+ * Returns a tiny hash value for the 'text'.
+ *
+ * Tiny hash function inspired from pearson
+ */
+uint8_t pearson4(const char *text)
+{
+       static uint8_t T[16] = {
+                4,  1,  6,  0,  9, 14, 11,  5,
+                2,  3, 12, 15, 10,  7,  8, 13
+       };
+       uint8_t r, c;
+
+       for (r = 0; (c = (uint8_t)*text) ; text++) {
+               r = T[r ^ (15 & c)];
+               r = T[r ^ (c >> 4)];
+       }
+       return r; // % HEADCOUNT;
+}
+