1 files changed, 53 insertions, 0 deletions
diff --git a/src/include/blobhash.h b/src/include/blobhash.h
new file mode 100644
index 000000000..303892b13
--- /dev/null
+++ b/src/include/blobhash.h
@@ -0,0 +1,53 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*- 
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2004-2006 Sage Weil <sage@newdream.net>
+ *
+ * This is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License version 2.1, as published by the Free Software 
+ * Foundation.  See file COPYING.
+ * 
+ */
+
+#ifndef CEPH_BLOBHASH_H
+#define CEPH_BLOBHASH_H
+
+#include <cstdint>
+#include "hash.h"
+
+class blobhash {
+public:
+  uint32_t operator()(const void* p, size_t len) {
+    static rjhash<std::uint32_t> H;
+    std::uint32_t acc = 0;
+    auto buf = static_cast<const unsigned char*>(p);
+    while (len >= sizeof(acc)) {
+      acc ^= unaligned_load(buf);
+      buf += sizeof(std::uint32_t);
+      len -= sizeof(std::uint32_t);
+    }
+    // handle the last few bytes of p[-(len % 4):]
+    switch (len) {
+    case 3:
+      acc ^= buf[2] << 16;
+      [[fallthrough]];
+    case 2:
+      acc ^= buf[1] << 8;
+      [[fallthrough]];
+    case 1:
+      acc ^= buf[0];
+    }
+    return H(acc);
+  }
+private:
+  static inline std::uint32_t unaligned_load(const unsigned char* p) {
+    std::uint32_t result;
+    __builtin_memcpy(&result, p, sizeof(result));
+    return result;
+  }
+};
+
+
+#endif