On 11/09/21 18:49, Richard W.M. Jones wrote:
> This commit makes no changes, it simply adds comments and breaks out
> the multiplcation into a local variable.
> ---
> common/utils/vector.c | 19 +++++++++++++++----
> 1 file changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/common/utils/vector.c b/common/utils/vector.c
> index d7120399..dff051e9 100644
> --- a/common/utils/vector.c
> +++ b/common/utils/vector.c
> @@ -42,20 +42,31 @@ int
> generic_vector_reserve (struct generic_vector *v, size_t n, size_t itemsize)
> {
> void *newptr;
> - size_t reqcap, newcap;
> + size_t reqcap, reqbytes, newcap, newbytes;
>
> + /* New capacity requested. We must allocate this minimum (or fail). */
> reqcap = v->cap + n;
> - if (reqcap * itemsize < v->cap * itemsize) {
> + reqbytes = reqcap * itemsize;
> + if (reqbytes < v->cap * itemsize) {
> errno = ENOMEM;
> return -1; /* overflow */
> }
>
> + /* However for the sake of optimization, scale buffer by 3/2 so that
> + * repeated reservations don't call realloc often.
> + */
> newcap = v->cap + (v->cap + 1) / 2;
> + newbytes = newcap * itemsize;
>
> - if (newcap * itemsize < reqcap * itemsize)
> + if (newbytes < reqbytes) {
> + /* If that either overflows or is less than the minimum requested,
> + * fall back to the requested capacity.
> + */
> newcap = reqcap;
> + newbytes = reqbytes;
> + }
>
> - newptr = realloc (v->ptr, newcap * itemsize);
> + newptr = realloc (v->ptr, newbytes);
> if (newptr == NULL)
> return -1;
> v->ptr = newptr;
>
Acked-by: Laszlo Ersek <[email protected]>
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