[#BloombergLP-bdlb-BitMaskUtil-le64]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdlb.adoc[bdlb]::xref:BloombergLP/bdlb/BitMaskUtil.adoc[BitMaskUtil]::le64
:relfileprefix: ../../../
:mrdocs:

Return a mask with all bits at or below `index` set.

== Synopsis

Declared in `<bdlb_bitmaskutil.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
static
uint64_t
le64(int index);
----

== Description

Return the unsigned integral value having all bits at positions less than or equal to the specified `index` set to 1, and all other bits set to 0. The behavior is undefined unless `0 <= index <= # of bits in result`.

== Return Value

mask with all bits at or below `index` set

== Parameters

[cols="1,4"]
|===
| Name| Description
| *index*
| highest bit position that is set
|===


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