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Harden bm_read_player_ship against invalid model numbers

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Eliminate an unnecessary internal copy.  Terminate the search early if
an invalid model number is used.
This commit is contained in:
Kp 2022-06-05 17:44:53 +00:00
parent 504e950b75
commit 0faa33d3df
1 changed files with 30 additions and 19 deletions
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49
similar/main/bmread.cpp
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@ -76,6 +76,7 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION. ALL RIGHTS RESERVED.
#include "partial_range.h"
#include "d_enumerate.h"
#include "d_range.h"
#include "d_zip.h"
using std::min;
@ -2044,28 +2045,38 @@ void bm_read_player_ship(void)
//calc player gun positions
{
polymodel *pm;
robot_info *r;
vms_vector pnt;
int mn; //submodel number
int gun_num;
r = &ri;
pm = &Polygon_models[Player_ship->model_num];
for (gun_num=0;gun_num<r->n_guns;gun_num++) {
pnt = r->gun_points[gun_num];
mn = r->gun_submodels[gun_num];
const auto &r = ri;
const auto &pm = Polygon_models[Player_ship->model_num];
/* Binding to the zip iterator produces references. For r.gun_points
* and r.gun_submodels, a mutable local is desired instead.
*
* If there are no submodels, copy directly from `r.gun_points` to
* `plr_gun_point` (bound to an element of `Player_ship->gun_points`).
*
* If there are submodels:
* - Copy the submodel index into a local `mn`
* - Copy the r.gun_points vector into a local `pnt`
* - Redirect `ppnt` to the local.
* - Update the local as needed from the polygon models.
* - Copy that local to `plr_gun_point`.
*
* This minimizes unnecessary copying.
*/
for (auto &&[rpnt, rmn, plr_gun_point] : zip(partial_range(r.gun_points, r.n_guns), r.gun_submodels, Player_ship->gun_points))
{
auto ppnt = &rpnt;
/* Create a local copy to be modified by the `while` loop. */
vms_vector pnt;
if (auto mn = rmn)
{
//instance up the tree for this gun
while (mn != 0) {
vm_vec_add2(pnt,pm->submodel_offsets[mn]);
mn = pm->submodel_parents[mn];
pnt = rpnt;
ppnt = &pnt;
for (; mn && mn < std::size(pm.submodel_offsets); mn = pm.submodel_parents[mn])
vm_vec_add2(pnt, pm.submodel_offsets[mn]);
}
Player_ship->gun_points[gun_num] = pnt;
plr_gun_point = *ppnt;
}
}
}