libcamera: utils: Add enumerate view for range-based for loops

Range-based for loops are handy and widely preferred in C++, but are
limited in their ability to replace for loops that require access to a
loop counter.  The enumerate() function solves this problem by wrapping
the iterable in an adapter that, when used as a range-expression, will
provide iterators whose value_type is a pair of index and value
reference.

The iterable must support std::begin() and std::end(). This includes all
containers provided by the standard C++ library, as well as C-style
arrays.

A typical usage pattern would use structured binding to store the index
and value in two separate variables:

std::vector<int> values = ...;

for (auto [index, value] : utils::enumerate(values)) {
     ...
}

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

0 files changed, 0 insertions, 0 deletions