[#BloombergLP-bslh-SipHashAlgorithm]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bslh.adoc[bslh]::SipHashAlgorithm
:relfileprefix: ../../
:mrdocs:

This class wraps an implementation of the &quot;SipHash&quot; algorithm in an interface that is usable in the modular hashing system in `bslh`&period;

== Synopsis

Declared in `&lt;bslh&lowbar;siphashalgorithm&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
class SipHashAlgorithm;
----

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslh/SipHashAlgorithm/result_type.adoc[`result&lowbar;type`] 
| Typedef indicating the value type returned by this algorithm&period;
|===


== Enums

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslh/SipHashAlgorithm/_04enum.adoc[`Unnamed enum`] 
| Compile&hyphen;time constants for the SipHash algorithm&period;
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslh/SipHashAlgorithm/2constructor.adoc[`SipHashAlgorithm`]         [.small]#[constructor]#
| Create a `bslh&colon;&colon;SipHashAlgorithm`, seeded with a 128&hyphen;bit (`k&lowbar;SEED&lowbar;LENGTH` bytes) seed pointed to by the specified `seed`&period; Each bit of the supplied seed will contribute to the final hash produced by `computeHash()`&period; The behaviour is undefined unless `seed` points to at least 16 bytes of initialized memory&period; Note that if data in `seed` is not random, all guarantees of security and Denial of Service (DoS) protection are void&period;
| xref:BloombergLP/bslh/SipHashAlgorithm/computeHash.adoc[`computeHash`] 
| Return the finalized version of the hash that has been accumulated&period; Note that this changes the internal state of the object, so calling `computeHash()` multiple times in a row will return different results, and only the first result returned will match the expected result of the algorithm&period; Also note that a value will be returned, even if data has not been passed into `operator()`
| xref:BloombergLP/bslh/SipHashAlgorithm/operator_call.adoc[`operator()`] 
| Incorporate the specified `data`, of at least the specified `numBytes`, into the internal state of the hashing algorithm&period; Every bit of data incorporated into the internal state of the algorithm will contribute to the final hash produced by `computeHash()`&period; The same hash will be produced regardless of whether a sequence of bytes is passed in all at once or through multiple calls to this member function&period; Input where `numBytes` is 0 will have no effect on the internal state of the algorithm&period; The behaviour is undefined unless `data` points to a valid memory location with at least `numBytes` bytes of initialized memory&period;
|===


== Data Members

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslh/SipHashAlgorithm/d_alignment.adoc[`d&lowbar;alignment`] [.small]#[variant member]#
| Ensures proper alignment for buffered data&period;
| xref:BloombergLP/bslh/SipHashAlgorithm/d_buf.adoc[`d&lowbar;buf`] [.small]#[variant member]#
| Used to buffer data until we have enough to do a full round of computation as specified by the algorithm&period;
|===



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