[#absl-ExtendCrc32c]
= xref:absl.adoc[absl]::ExtendCrc32c
:relfileprefix: ../
:mrdocs:

Compute a CRC32C value from an existing value and an additional buffer.

== Synopsis

Declared in `<absl/crc/crc32c.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:absl/crc32c_t.adoc[crc32c_t]
ExtendCrc32c(
    xref:absl/crc32c_t.adoc[crc32c_t] initial_crc,
    std::string_view buf_to_add);
----

== Description

Computes a CRC32C value from an `initial_crc` CRC32C value including the `buf_to_add` bytes of an additional buffer. Using this function is more efficient than computing a CRC32C value for the combined buffer from scratch.

Note: `ExtendCrc32c` with an initial_crc of 0 is equivalent to `ComputeCrc32c`.

This operation has a runtime cost of O(`buf_to_add.size()`)

== Return Value

The CRC32C value of the combined buffer.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *initial_crc*
| The CRC32C value of the bytes already processed.
| *buf_to_add*
| The additional bytes to include in the checksum.
|===


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