Re: [PATCH 23/35] perf tools: Add reallocarray_as_needed()

[Ian Rogers]

On Mon, Jul 11, 2022 at 2:33 AM Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
>
> Add helper reallocarray_as_needed() to reallocate an array to a larger
> size and initialize the extra entries to an arbitrary value.
>
> Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> ---
>  tools/perf/util/util.c | 33 +++++++++++++++++++++++++++++++++
>  tools/perf/util/util.h | 15 +++++++++++++++
>  2 files changed, 48 insertions(+)
>
> diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
> index 9b02edf9311d..391c1e928bd7 100644
> --- a/tools/perf/util/util.c
> +++ b/tools/perf/util/util.c
> @@ -18,6 +18,7 @@
>  #include <linux/kernel.h>
>  #include <linux/log2.h>
>  #include <linux/time64.h>
> +#include <linux/overflow.h>
>  #include <unistd.h>
>  #include "cap.h"
>  #include "strlist.h"
> @@ -500,3 +501,35 @@ char *filename_with_chroot(int pid, const char *filename)
>
>         return new_name;
>  }
> +
> +/*
> + * Reallocate an array *arr of size *arr_sz so that it is big enough to contain
> + * x elements of size msz, initializing new entries to *init_val or zero if
> + * init_val is NULL
> + */
> +int do_realloc_array_as_needed(void **arr, size_t *arr_sz, size_t x, size_t msz, const void *init_val)

This feels a little like a 1-dimensional xyarray, could we make a
similar abstraction to avoid passing all these values around?

Thanks,
Ian

> +{
> +       size_t new_sz = *arr_sz;
> +       void *new_arr;
> +       size_t i;
> +
> +       if (!new_sz)
> +               new_sz = msz >= 64 ? 1 : roundup(64, msz); /* Start with at least 64 bytes */
> +       while (x >= new_sz) {
> +               if (check_mul_overflow(new_sz, (size_t)2, &new_sz))
> +                       return -ENOMEM;
> +       }
> +       if (new_sz == *arr_sz)
> +               return 0;
> +       new_arr = calloc(new_sz, msz);
> +       if (!new_arr)
> +               return -ENOMEM;
> +       memcpy(new_arr, *arr, *arr_sz * msz);
> +       if (init_val) {
> +               for (i = *arr_sz; i < new_sz; i++)
> +                       memcpy(new_arr + (i * msz), init_val, msz);
> +       }
> +       *arr = new_arr;
> +       *arr_sz = new_sz;
> +       return 0;
> +}
> diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h
> index 0f78f1e7782d..c1f2d423a9ec 100644
> --- a/tools/perf/util/util.h
> +++ b/tools/perf/util/util.h
> @@ -79,4 +79,19 @@ struct perf_debuginfod {
>  void perf_debuginfod_setup(struct perf_debuginfod *di);
>
>  char *filename_with_chroot(int pid, const char *filename);
> +
> +int do_realloc_array_as_needed(void **arr, size_t *arr_sz, size_t x,
> +                              size_t msz, const void *init_val);
> +
> +#define realloc_array_as_needed(a, n, x, v) ({                 \
> +       typeof(x) __x = (x);                                    \
> +       __x >= (n) ?                                            \
> +               do_realloc_array_as_needed((void **)&(a),       \
> +                                          &(n),                \
> +                                          __x,                 \
> +                                          sizeof(*(a)),        \
> +                                          (const void *)(v)) : \
> +               0;                                              \
> +       })
> +
>  #endif /* GIT_COMPAT_UTIL_H */
> --
> 2.25.1
>