Diff: Hashes/sfh_mbed.cpp

Revision:

13:8b706583610a

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Hashes/sfh_mbed.cpp	Tue May 09 03:06:55 2017 +0000
@@ -0,0 +1,73 @@
+#include "sfh_mbed.h"
+#include "SlidingWindow.h"
+#include "LookupTable.h"
+
+#define LOOKUP_TABLE_SIZE 3000
+#define SLIDING_WINDOW_SIZE 300
+
+//static uint32_t sliding_window_index = 0; 
+
+
+uint32_t hash (const char *data, uint16_t len) {
+    // This is mostly Paul Hsieh's original code
+    uint32_t hash, tmp;
+    int rem;
+
+    if (len <= 0 || data == 0) {
+        return 0;
+    }
+
+    hash = len;
+    rem = len & 3;
+    len >>= 2;
+
+    /* Main loop */
+    while (len > 0) {
+        hash += *((uint16_t *) data);
+
+        /* To make a long story short, the C standard states that the
+         * shift operator's operands must be promoted to (unsigned) int,
+         * which is (usually) 32 bits wide on PC and 16 on Arduino. This
+         * results in different behaviour, since part of the result gets
+         * truncated on Arduino, so we cast the result to make sure all
+         * bits are kept.
+         */
+        tmp = ((uint32_t) (*((uint16_t *) (data + 2))) << 11) ^ hash;
+
+        hash = (hash << 16) ^ tmp;
+        data += 2 * sizeof (uint16_t);
+        hash += hash >> 11;
+        len--;
+    }
+
+    /* Handle end cases */
+    switch (rem) {
+        case 3:
+            hash += * ((uint16_t *) data);
+            hash ^= hash << 16;
+            hash ^= ((signed char) data[2]) << 18;
+            hash += hash >> 11;
+            break;
+
+        case 2:
+            hash += * ((uint16_t *) data);
+            hash ^= hash << 11;
+            hash += hash >> 17;
+            break;
+
+        case 1:
+            hash += (signed char) * data;
+            hash ^= hash << 10;
+            hash += hash >> 1;
+    }
+
+    /* Force "avalanching" of final 127 bits */
+    hash ^= hash << 3;
+    hash += hash >> 5;
+    hash ^= hash << 4;
+    hash += hash >> 17;
+    hash ^= hash << 25;
+    hash += hash >> 6;
+
+    return hash;
+}
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