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Be careful to avoid undefined behavior from shifting negative numbers

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This commit is contained in:
Eric Fischer
2019-06-17 17:50:25 -07:00
parent b550c7b4a6
commit fc335e2221
4 changed files with 27 additions and 14 deletions
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serial.cpp
+16 -11
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@@ -21,6 +21,11 @@
#include "evaluator.hpp"
#include "milo/dtoa_milo.h"
// Offset coordinates to keep them positive
#define COORD_OFFSET (4LL << 32)
#define SHIFT_RIGHT(a) ((((a) + COORD_OFFSET) >> geometry_scale) - (COORD_OFFSET >> geometry_scale))
#define SHIFT_LEFT(a) ((((a) + (COORD_OFFSET >> geometry_scale)) << geometry_scale) - COORD_OFFSET)
size_t fwrite_check(const void *ptr, size_t size, size_t nitems, FILE *stream, const char *fname) {
size_t w = fwrite(ptr, size, nitems, stream);
if (w != nitems) {
@@ -359,8 +364,8 @@ static long long scale_geometry(struct serialization_state *sst, long long *bbox
*(sst->initial_x) = 1LL << 31;
*(sst->initial_y) = 1LL << 31;
} else {
*(sst->initial_x) = (x >> geometry_scale) << geometry_scale;
*(sst->initial_y) = (y >> geometry_scale) << geometry_scale;
*(sst->initial_x) = (((x + COORD_OFFSET) >> geometry_scale) << geometry_scale) - COORD_OFFSET;
*(sst->initial_y) = (((y + COORD_OFFSET) >> geometry_scale) << geometry_scale) - COORD_OFFSET;
}
*(sst->initialized) = 1;
@@ -374,8 +379,8 @@ static long long scale_geometry(struct serialization_state *sst, long long *bbox
geom[i].x = std::round(x * scale);
geom[i].y = std::round(y * scale);
} else {
geom[i].x = x >> geometry_scale;
geom[i].y = y >> geometry_scale;
geom[i].x = SHIFT_RIGHT(x);
geom[i].y = SHIFT_RIGHT(y);
}
}
}
@@ -412,12 +417,12 @@ int serialize_feature(struct serialization_state *sst, serial_feature &sf) {
for (auto &c : clipbboxes) {
if (sf.t == VT_POLYGON) {
sf.geometry = simple_clip_poly(sf.geometry, c.minx >> geometry_scale, c.miny >> geometry_scale, c.maxx >> geometry_scale, c.maxy >> geometry_scale);
sf.geometry = simple_clip_poly(sf.geometry, SHIFT_RIGHT(c.minx), SHIFT_RIGHT(c.miny), SHIFT_RIGHT(c.maxx), SHIFT_RIGHT(c.maxy));
} else if (sf.t == VT_LINE) {
sf.geometry = clip_lines(sf.geometry, c.minx >> geometry_scale, c.miny >> geometry_scale, c.maxx >> geometry_scale, c.maxy >> geometry_scale);
sf.geometry = clip_lines(sf.geometry, SHIFT_RIGHT(c.minx), SHIFT_RIGHT(c.miny), SHIFT_RIGHT(c.maxx), SHIFT_RIGHT(c.maxy));
sf.geometry = remove_noop(sf.geometry, sf.t, 0);
} else if (sf.t == VT_POINT) {
sf.geometry = clip_point(sf.geometry, c.minx >> geometry_scale, c.miny >> geometry_scale, c.maxx >> geometry_scale, c.maxy >> geometry_scale);
sf.geometry = clip_point(sf.geometry, SHIFT_RIGHT(c.minx), SHIFT_RIGHT(c.miny), SHIFT_RIGHT(c.maxx), SHIFT_RIGHT(c.maxy));
}
sf.bbox[0] = LLONG_MAX;
@@ -426,8 +431,8 @@ int serialize_feature(struct serialization_state *sst, serial_feature &sf) {
sf.bbox[3] = LLONG_MIN;
for (auto &g : sf.geometry) {
long long x = g.x << geometry_scale;
long long y = g.y << geometry_scale;
long long x = SHIFT_LEFT(g.x);
long long y = SHIFT_LEFT(g.y);
if (x < sf.bbox[0]) {
sf.bbox[0] = x;
@@ -460,7 +465,7 @@ int serialize_feature(struct serialization_state *sst, serial_feature &sf) {
std::vector<unsigned long long> locs;
for (size_t i = 0; i < sf.geometry.size(); i++) {
if (sf.geometry[i].op == VT_MOVETO || sf.geometry[i].op == VT_LINETO) {
locs.push_back(encode_index(sf.geometry[i].x << geometry_scale, sf.geometry[i].y << geometry_scale));
locs.push_back(encode_index(SHIFT_LEFT(sf.geometry[i].x), SHIFT_LEFT(sf.geometry[i].y)));
}
}
std::sort(locs.begin(), locs.end());
@@ -662,7 +667,7 @@ int serialize_feature(struct serialization_state *sst, serial_feature &sf) {
}
long long geomstart = r->geompos;
serialize_feature(r->geomfile, &sf, &r->geompos, sst->fname, *(sst->initial_x) >> geometry_scale, *(sst->initial_y) >> geometry_scale, false);
serialize_feature(r->geomfile, &sf, &r->geompos, sst->fname, SHIFT_RIGHT(*(sst->initial_x)), SHIFT_RIGHT(*(sst->initial_y)), false);
struct index index;
index.start = geomstart;