Update xxhash.adoc

doc/hash2/reference/xxhash.adoc

@@ -19,7 +19,171 @@ class xxhash_64;
 } // namespace boost
 ```
 
+This header implements the https://xxhash.com/[XXH32 and XXH64 algorithms].
+
 ## xxhash_32
 
+```
+class xxhash_32
+{
+public:
+
+    using result_type = std::uint32_t;
+
+    constexpr xxhash_32();
+    explicit constexpr xxhash_32( std::uint64_t seed );
+    constexpr xxhash_32( unsigned char const* p, std::size_t n );
+
+    void update( void const* p, std::size_t n );
+    constexpr void update( unsigned char const* p, std::size_t n );
+
+    constexpr result_type result();
+};
+```
+
+### Constructors
+
+```
+constexpr xxhash_32();
+```
+
+Default constructor.
+
+Effects: ::
+  Initializes the internal state of the XXH32 algorithm to its initial values.
+
+```
+explicit constexpr xxhash_32( std::uint64_t seed );
+```
+
+Constructor taking an integral seed value.
+
+Effects: ::
+  Initializes the internal state of the XXH32 algorithm using the low 32 bits of `seed` as the seed, then if the high 32 bits of `seed` aren't zero, mixes them into the state.
+
+Remarks: ::
+  By convention, if `seed` is zero, the effect of this constructor is the same as default construction.
+
+```
+xxhash_32( unsigned char const* p, std::size_t n );
+```
+
+Constructor taking a byte sequence seed.
+
+Effects: ::
+  Initializes the state as if by default construction, then if `n` is not zero, performs `update(p, n); result()`.
+
+Remarks: ::
+  By convention, if `n` is zero, the effect of this constructor is the same as default construction.
+
+### update
+
+```
+void update( void const* p, std::size_t n );
+constexpr void update( unsigned char const* p, std::size_t n );
+```
+
+Effects: ::
+  Updates the internal state of the XXH32 algorithm from the byte sequence `[p, p+n)`.
+
+Remarks: ::
+  Consecutive calls to `update` are equivalent to a single call with the concatenated byte sequences of the individual calls.
+
+### result
+
+```
+constexpr result_type result();
+```
+
+Effects: ::
+  Obtains a 32 bit hash value from the state as specified by XXH32, then updates the state.
+
+Returns: ::
+  The obtained hash value.
+
+Remarks: ::
+  The state is updated to allow repeated calls to `result()` to return a pseudorandom sequence of `result_type` values, effectively extending the output.
+
 ## xxhash_64
 
+```
+class xxhash_64
+{
+public:
+
+    using result_type = std::uint64_t;
+
+    constexpr xxhash_64();
+    explicit constexpr xxhash_64( std::uint64_t seed );
+    constexpr xxhash_64( unsigned char const* p, std::size_t n );
+
+    void update( void const* p, std::size_t n );
+    constexpr void update( unsigned char const* p, std::size_t n );
+
+    constexpr result_type result();
+};
+```
+
+### Constructors
+
+```
+constexpr xxhash_64();
+```
+
+Default constructor.
+
+Effects: ::
+  Initializes the internal state of the XXH64 algorithm to its initial values.
+
+```
+explicit constexpr xxhash_64( std::uint64_t seed );
+```
+
+Constructor taking an integral seed value.
+
+Effects: ::
+  Initializes the internal state of the XXH64 algorithm using `seed` as the seed.
+
+Remarks: ::
+  By convention, if `seed` is zero, the effect of this constructor is the same as default construction.
+
+```
+xxhash_64( unsigned char const* p, std::size_t n );
+```
+
+Constructor taking a byte sequence seed.
+
+Effects: ::
+  Initializes the state as if by default construction, then if `n` is not zero, performs `update(p, n); result()`.
+
+Remarks: ::
+  By convention, if `n` is zero, the effect of this constructor is the same as default construction.
+
+### update
+
+```
+void update( void const* p, std::size_t n );
+constexpr void update( unsigned char const* p, std::size_t n );
+```
+
+Effects: ::
+  Updates the internal state of the XXH64 algorithm from the byte sequence `[p, p+n)`.
+
+Remarks: ::
+  Consecutive calls to `update` are equivalent to a single call with the concatenated byte sequences of the individual calls.
+
+### result
+
+```
+constexpr result_type result();
+```
+
+Effects: ::
+  Obtains a 64 bit hash value from the state as specified by XXH64, then updates the state.
+
+Returns: ::
+  The obtained hash value.
+
+Remarks: ::
+  The state is updated to allow repeated calls to `result()` to return a pseudorandom sequence of `result_type` values, effectively extending the output.
+