[#HashWriter]
= HashWriter
:mrdocs:

A writer stream (for serialization) that computes a 256‐bit hash.

== Synopsis

Declared in `<hash.h>`

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

== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:HashWriter/GetCheapHash.adoc[`GetCheapHash`] 
| Returns the first 64 bits from the resulting hash.
| xref:HashWriter/GetHash.adoc[`GetHash`] 
| Compute the double‐SHA256 hash of all data written to this object.
| xref:HashWriter/GetSHA256.adoc[`GetSHA256`] 
| Compute the SHA256 hash of all data written to this object.
| xref:HashWriter/write.adoc[`write`] 
| Adds data to the running hash.
| xref:HashWriter/operator_lshift.adoc[`operator<<`] 
| Serializes an object into the running hash.
|===


== Non-Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:TaggedHash.adoc[`TaggedHash`]
| Return a HashWriter primed for tagged hashes (as specified in BIP 340).
|===

== Derived Classes

[cols="1,4"]
|===
| Name| Description
| xref:HashVerifier.adoc[`HashVerifier`] 
| Reads data from an underlying stream, while hashing the read data.
| xref:HashedSourceWriter.adoc[`HashedSourceWriter`] 
| Writes data to an underlying source stream, while hashing the written data.
|===


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