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

Ian Rogers
2022-07-20T00:56:13Z

On Mon, Jul 11, 2022 at 2:33 AM Adrian Hunter <adrian.hunter@intel.com> 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@intel.com>
> ---
> 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
>