Move hash.h/cc from net to base.

Review URL: https://chromiumcodereview.appspot.com/10920026

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@154554 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 73 insertions, 0 deletions

diff --git a/base/hash.cc b/base/hash.cc
new file mode 100644
index 0000000..2c87065
--- /dev/null
+++ b/base/hash.cc
@@ -0,0 +1,73 @@
+// From http://www.azillionmonkeys.com/qed/hash.html
+
+#include "base/hash.h"
+
+typedef uint32 uint32_t;
+typedef uint16 uint16_t;
+
+namespace base {
+
+#undef get16bits
+#if (defined(__GNUC__) && defined(__i386__)) || defined(__WATCOMC__) \
+  || defined(_MSC_VER) || defined (__BORLANDC__) || defined (__TURBOC__)
+#define get16bits(d) (*((const uint16_t *) (d)))
+#endif
+
+#if !defined (get16bits)
+#define get16bits(d) ((((uint32_t)(((const uint8_t *)(d))[1])) << 8)\
+                       +(uint32_t)(((const uint8_t *)(d))[0]) )
+#endif
+
+uint32 SuperFastHash(const char * data, int len) {
+  uint32_t hash = len, tmp;
+  int rem;
+
+  if (len <= 0 || data == NULL)
+    return 0;
+
+  rem = len & 3;
+  len >>= 2;
+
+  /* Main loop */
+  for (; len > 0; len--) {
+    hash  += get16bits(data);
+    tmp    = (get16bits(data + 2) << 11) ^ hash;
+    hash   = (hash << 16) ^ tmp;
+    data  += 2 * sizeof(uint16_t);
+    hash  += hash >> 11;
+  }
+
+  /* Handle end cases */
+  switch (rem) {
+    case 3:
+      hash += get16bits(data);
+      hash ^= hash << 16;
+
+      // Treat the final character as signed. This ensures all platforms behave
+      // consistently with the original x86 code.
+      hash ^= static_cast<signed char>(data[sizeof(uint16_t)]) << 18;
+      hash += hash >> 11;
+      break;
+    case 2:
+      hash += get16bits(data);
+      hash ^= hash << 11;
+      hash += hash >> 17;
+      break;
+    case 1:
+      hash += static_cast<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;
+}
+
+}  // namespace base