[#BloombergLP-bdlb-BitMaskUtil-one]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdlb.adoc[bdlb]::xref:BloombergLP/bdlb/BitMaskUtil.adoc[BitMaskUtil]::one
:relfileprefix: ../../../
:mrdocs:

Return a mask with `numBits` bits set starting at `index`.

== Synopsis

Declared in `<bdlb_bitmaskutil.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
static
uint32_t
one(
    int index,
    int numBits);
----

== Description

Return the unsigned integral value having the specified `numBits` starting at the specified `index` set to 1, and all other bits set to 0. The behavior is undefined unless `0 <= index`, `0 <= numBits`, and `index + numBits <= # of bits in result`.

== Return Value

mask with `numBits` bits set starting at `index`

== Parameters

[cols="1,4"]
|===
| Name| Description
| *index*
| starting bit position of the range to set
| *numBits*
| number of consecutive bits to set
|===


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