Revert D6050464: [Folly] Move folly/Hash.h to folly/hash/

[folly.git] / folly / Hash.h

diff --git a/folly/Hash.h b/folly/Hash.h
index 77ba5878f17e6502c0c89a0e2fbe42f8c4dc757f..410d2720db540cf6c586ed91f7597a92c9463daa 100644 (file)
--- a/folly/Hash.h
+++ b/folly/Hash.h
@@ -26,8 +26,8 @@
 
 #include <folly/ApplyTuple.h>
 #include <folly/Bits.h>
-#include <folly/SpookyHashV1.h>
-#include <folly/SpookyHashV2.h>
+#include <folly/hash/SpookyHashV1.h>
+#include <folly/hash/SpookyHashV2.h>
 
 /*
  * Various hashing functions.
@@ -214,6 +214,7 @@ inline uint32_t jenkins_rev_unmix32(uint32_t key) {
 
 const uint32_t FNV_32_HASH_START = 2166136261UL;
 const uint64_t FNV_64_HASH_START = 14695981039346656037ULL;
+const uint64_t FNVA_64_HASH_START = 14695981039346656037ULL;
 
 inline uint32_t fnv32(const char* buf, uint32_t hash = FNV_32_HASH_START) {
   // forcing signed char, since other platforms can use unsigned
@@ -278,6 +279,24 @@ inline uint64_t fnv64(const std::string& str,
   return fnv64_buf(str.data(), str.size(), hash);
 }
 
+inline uint64_t fnva64_buf(const void* buf,
+                           size_t n,
+                           uint64_t hash = FNVA_64_HASH_START) {
+  const uint8_t* char_buf = reinterpret_cast<const uint8_t*>(buf);
+
+  for (size_t i = 0; i < n; ++i) {
+    hash ^= char_buf[i];
+    hash += (hash << 1) + (hash << 4) + (hash << 5) + (hash << 7) +
+            (hash << 8) + (hash << 40);
+  }
+  return hash;
+}
+
+inline uint64_t fnva64(const std::string& str,
+                       uint64_t hash = FNVA_64_HASH_START) {
+  return fnva64_buf(str.data(), str.size(), hash);
+}
+
 /*
  * Paul Hsieh: http://www.azillionmonkeys.com/qed/hash.html
  */
@@ -291,7 +310,7 @@ inline uint32_t hsieh_hash32_buf(const void* buf, size_t len) {
   uint32_t tmp;
   size_t rem;
 
-  if (len <= 0 || buf == 0) {
+  if (len <= 0 || buf == nullptr) {
     return 0;
   }
 
@@ -351,7 +370,24 @@ inline uint32_t hsieh_hash32_str(const std::string& str) {
 
 } // namespace hash
 
-template<class Key, class Enable = void>
+namespace detail {
+struct integral_hasher {
+  template <typename I>
+  size_t operator()(I const& i) const {
+    static_assert(sizeof(I) <= 8, "input type is too wide");
+    if (sizeof(I) <= 4) { // the branch taken is known at compile time
+      auto const i32 = static_cast<int32_t>(i); // impl accident: sign-extends
+      auto const u32 = static_cast<uint32_t>(i32);
+      return static_cast<size_t>(hash::jenkins_rev_mix32(u32));
+    } else {
+      auto const u64 = static_cast<uint64_t>(i);
+      return static_cast<size_t>(hash::twang_mix64(u64));
+    }
+  }
+};
+} // namespace detail
+
+template <class Key, class Enable = void>
 struct hasher;
 
 struct Hash {
@@ -374,63 +410,40 @@ struct hasher<bool> {
   }
 };
 
-template<> struct hasher<int32_t> {
-  size_t operator()(int32_t key) const {
-    return hash::jenkins_rev_mix32(uint32_t(key));
-  }
-};
+template <>
+struct hasher<unsigned long long> : detail::integral_hasher {};
 
-template<> struct hasher<uint32_t> {
-  size_t operator()(uint32_t key) const {
-    return hash::jenkins_rev_mix32(key);
-  }
-};
+template <>
+struct hasher<signed long long> : detail::integral_hasher {};
 
-template<> struct hasher<int16_t> {
-  size_t operator()(int16_t key) const {
-    return hasher<int32_t>()(key); // as impl accident, sign-extends
-  }
-};
+template <>
+struct hasher<unsigned long> : detail::integral_hasher {};
 
-template<> struct hasher<uint16_t> {
-  size_t operator()(uint16_t key) const {
-    return hasher<uint32_t>()(key);
-  }
-};
+template <>
+struct hasher<signed long> : detail::integral_hasher {};
 
-template<> struct hasher<int8_t> {
-  size_t operator()(int8_t key) const {
-    return hasher<int32_t>()(key); // as impl accident, sign-extends
-  }
-};
+template <>
+struct hasher<unsigned int> : detail::integral_hasher {};
 
-template<> struct hasher<uint8_t> {
-  size_t operator()(uint8_t key) const {
-    return hasher<uint32_t>()(key);
-  }
-};
+template <>
+struct hasher<signed int> : detail::integral_hasher {};
 
-template<> struct hasher<char> {
-  using explicit_type =
-      std::conditional<std::is_signed<char>::value, int8_t, uint8_t>::type;
-  size_t operator()(char key) const {
-    return hasher<explicit_type>()(key); // as impl accident, sign-extends
-  }
-};
+template <>
+struct hasher<unsigned short> : detail::integral_hasher {};
 
-template<> struct hasher<int64_t> {
-  size_t operator()(int64_t key) const {
-    return static_cast<size_t>(hash::twang_mix64(uint64_t(key)));
-  }
-};
+template <>
+struct hasher<signed short> : detail::integral_hasher {};
 
-template<> struct hasher<uint64_t> {
-  size_t operator()(uint64_t key) const {
-    return static_cast<size_t>(hash::twang_mix64(key));
-  }
-};
+template <>
+struct hasher<unsigned char> : detail::integral_hasher {};
+
+template <>
+struct hasher<signed char> : detail::integral_hasher {};
+
+template <> // char is a different type from both signed char and unsigned char
+struct hasher<char> : detail::integral_hasher {};
 
-template<> struct hasher<std::string> {
+template <> struct hasher<std::string> {
   size_t operator()(const std::string& key) const {
     return static_cast<size_t>(
         hash::SpookyHashV2::Hash64(key.data(), key.size(), 0));
@@ -486,7 +499,7 @@ namespace std {
   // items in the pair.
   template <typename T1, typename T2>
   struct hash<std::pair<T1, T2> > {
-  public:
+   public:
     size_t operator()(const std::pair<T1, T2>& x) const {
       return folly::hash::hash_combine(x.first, x.second);
     }