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

Adrian Hunter
2022-08-09T16:48:19Z

On 20/07/22 03:55, Ian Rogers wrote:
> 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?

xyarray does not realloc which is the only thing that is needed in
this case. C isn't C++, so adding an abstraction would be clunky.

>
> 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
>>