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;
--
2.32.0
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