[libcamera-devel] [RFC PATCH v1 01/12] libcamera: base: utils: Use size_t for index in utils::enumerate()

[Hirokazu Honda]

Hi Laurent, thank you for the patch.

On Thu, Sep 2, 2021 at 5:28 PM Laurent Pinchart
<laurent.pinchart at ideasonboard.com> wrote:
>
> Hi Kieran,
>
> On Thu, Sep 02, 2021 at 08:48:44AM +0100, Kieran Bingham wrote:
> > On 02/09/2021 05:22, Laurent Pinchart wrote:
> > > The index generated by utils::enumerate() is an iteration counter, which
> > > should thus be positive. Use std::size_t instead of the different_type
> > > of the container.
> > >
> > > Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> >
> > No other changes required elsewhere?
>
> As far as the compiler tells me :-)
>
> > I guess that means the update is not particularly invasive, and the
> > existing users will be fine.
> >
> > Given that looking at the recommended usage for this is with auto, I
> > guess that means the type is automatically updated for those users:
> >
> > src/v4l2/v4l2_compat_manager.cpp:
> >        for (auto [index, camera] : utils::enumerate(cameras)) {
>
> Yes. It makes a difference when using index though, is comparing it to a
> signed value will now produce a warning (hence the changes in the test).
> There are no other usage of the variable that the compiler is unhappy
> about.
>
> > So this looks fine.
> >
> > Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> >
> > > ---
> > >  include/libcamera/base/utils.h |  4 ++--
> > >  test/utils.cpp                 | 10 +++++-----
> > >  2 files changed, 7 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/include/libcamera/base/utils.h b/include/libcamera/base/utils.h
> > > index 52301254c2eb..2b761436a99f 100644
> > > --- a/include/libcamera/base/utils.h
> > > +++ b/include/libcamera/base/utils.h
> > > @@ -246,7 +246,7 @@ private:
> > >
> > >  public:
> > >     using difference_type = typename std::iterator_traits<Base>::difference_type;
> > > -   using value_type = std::pair<const difference_type, base_reference>;
> > > +   using value_type = std::pair<const std::size_t, base_reference>;
> > >     using pointer = value_type *;
> > >     using reference = value_type &;
> > >     using iterator_category = std::input_iterator_tag;
> > > @@ -275,7 +275,7 @@ public:
> > >
> > >  private:
> > >     Base current_;
> > > -   difference_type pos_;
> > > +   std::size_t pos_;
> > >  };
> > >
> > >  template<typename Base>
> > > diff --git a/test/utils.cpp b/test/utils.cpp
> > > index d7f810e95e7a..d65467b5102c 100644
> > > --- a/test/utils.cpp
> > > +++ b/test/utils.cpp
> > > @@ -77,8 +77,8 @@ protected:
> > >
> > >     int testEnumerate()
> > >     {
> > > -           std::vector<int> integers{ 1, 2, 3, 4, 5 };
> > > -           int i = 0;
> > > +           std::vector<unsigned int> integers{ 1, 2, 3, 4, 5 };
> > > +           unsigned int i = 0;
> > >
> > >             for (auto [index, value] : utils::enumerate(integers)) {
> > >                     if (index != i || value != i + 1) {
> > > @@ -93,12 +93,12 @@ protected:
> > >                     ++i;
> > >             }
> > >
> > > -           if (integers != std::vector<int>{ 0, 1, 2, 3, 4 }) {
> > > +           if (integers != std::vector<unsigned int>{ 0, 1, 2, 3, 4 }) {
> > >                     cerr << "Failed to modify container in enumerated range loop" << endl;
> > >                     return TestFail;
> > >             }
> > >
> > > -           Span<const int> span{ integers };
> > > +           Span<const unsigned int> span{ integers };
> > >             i = 0;
> > >
> > >             for (auto [index, value] : utils::enumerate(span)) {
> > > @@ -112,7 +112,7 @@ protected:
> > >                     ++i;
> > >             }
> > >
> > > -           const int array[] = { 0, 2, 4, 6, 8 };
> > > +           const unsigned int array[] = { 0, 2, 4, 6, 8 };
> > >             i = 0;
> > >
> > >             for (auto [index, value] : utils::enumerate(array)) {
> > >
>

Reviewed-by: Hirokazu Honda <hiroh at chromium.org>

-Hiro
> --
> Regards,
>
> Laurent Pinchart