Inconsistent capacity handling in `HeaderMap::with_capacity`

[qwaz]

http/src/header/map.rs

Line 473 in 9c05e39

entries: Vec::with_capacity(raw_cap),

http/src/header/map.rs

Line 635 in 9c05e39

self.entries = Vec::with_capacity(usable_capacity(cap));

http/src/header/map.rs

Line 1592 in 9c05e39

self.entries = Vec::with_capacity(usable_capacity(new_raw_cap));

HeaderMap::with_capacity reserves the entry vector with Vec::with_capacity(raw_cap), while other functions reserves the same entry with Vec::with_capacity(usable_capacity(raw_cap)).

[hawkw]

@qwaz could you provide some additional details on why this is incorrect? Thanks!

[qwaz]

@hawkw This is not an incorrect code in terms of correctness, but we can improve the consistency of the code and save a bit of memory by changing HeaderMap::with_capacity to use Vec::with_capacity(usable_capacity(raw_cap)) instead of Vec::with_capacity(raw_cap).

[hawkw]

@qwaz ah, okay, I misunderstood — I thought that since this was linked in the "Audit http" issue on safety-dance, this was part of the security audit. Thanks for clearing that up.