intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 51 insertions, 0 deletions

diff --git a/library/cpp/digest/sfh/sfh.h b/library/cpp/digest/sfh/sfh.h
new file mode 100644
index 0000000000..372938654c
--- /dev/null
+++ b/library/cpp/digest/sfh/sfh.h
@@ -0,0 +1,51 @@
+#pragma once
+
+#include <util/system/defaults.h>
+#include <util/system/unaligned_mem.h>
+
+inline ui32 SuperFastHash(const void* d, size_t l) noexcept {
+    ui32 hash = (ui32)l;
+    ui32 tmp;
+
+    if (!l || !d)
+        return 0;
+
+    TUnalignedMemoryIterator<ui16, 4> iter(d, l);
+
+    while (!iter.AtEnd()) {
+        hash += (ui32)iter.Next();
+        tmp = ((ui32)iter.Next() << 11) ^ hash;
+        hash = (hash << 16) ^ tmp;
+        hash += hash >> 11;
+    }
+
+    switch (iter.Left()) {
+        case 3:
+            hash += (ui32)iter.Next();
+            hash ^= hash << 16;
+            hash ^= ((ui32)(i32) * (const i8*)iter.Last()) << 18;
+            hash += hash >> 11;
+            break;
+
+        case 2:
+            hash += (ui32)iter.Cur();
+            hash ^= hash << 11;
+            hash += hash >> 17;
+            break;
+
+        case 1:
+            hash += *((const i8*)iter.Last());
+            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;
+}