Which search algorithm is used in the following code snippet?

int myfunction$($vector& array, int key$)$

$\{$

int index $=0$;

while $(($index $<$ array.size$())$ && $($key $!=$ array$[$index$]))$

$\{$

if $($array$[$index$]!=$ key$)\{$ index$++$; $\}$

$\}$

return index;

$\}$