[#BloombergLP-bdlde-Utf8CheckingInStreamBufWrapper-underflow]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdlde.adoc[bdlde]::xref:BloombergLP/bdlde/Utf8CheckingInStreamBufWrapper.adoc[Utf8CheckingInStreamBufWrapper]::underflow
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:mrdocs:

Replenish the input buffer and return the next input byte&period;

== Synopsis

Declared in `&lt;bdlde&lowbar;utf8checkinginstreambufwrapper&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
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virtual
int&lowbar;type
underflow() override;
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== Description

Replenish the input buffer with data obtained from the held `streambuf`, and return the next byte of input (or `eof` if no input is available)&period; This function assumes that either the input buffer is empty or that the end of it has been reached&period; If this object is not in a valid state, `eof` will be returned&period;

== Return Value

the next byte of input, or `eof` if no input is available or this object is not in a valid state


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