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Fix off-by-one in path finding logic #7682

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merged 2 commits into from
Jan 28, 2025
Merged

Fix off-by-one in path finding logic #7682

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e73acad
Fix off-by-one in path finding logic
StephenCWills Jan 28, 2025
00d08c0
Restrict tests to longest path length in vanilla Diablo
StephenCWills Jan 28, 2025
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4 changes: 2 additions & 2 deletions Source/engine/path.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -160,17 +160,17 @@
const auto it = explored.find(cur);
if (it == explored.end()) app_fatal("Failed to reconstruct path");
if (it->second.g == 0) break; // reached start
path[len++] = GetPathDirection(it->second.prev, cur);
cur = it->second.prev;
if (len == maxPathLength) {
// Path too long.
len = 0;
break;
}
path[len++] = GetPathDirection(it->second.prev, cur);
cur = it->second.prev;
}
std::reverse(path, path + len);
std::fill(path + len, path + maxPathLength, -1);
return len;

Check warning on line 173 in Source/engine/path.cpp

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 'return': conversion from 'size_t' to 'int', possible loss of data
}

} // namespace
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5 changes: 3 additions & 2 deletions test/path_test.cpp
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Expand Up @@ -91,7 +91,8 @@ std::vector<Dir> ToSyms(std::span<const int8_t> indices)

void CheckPath(Point startPosition, Point destinationPosition, std::vector<std::string> expectedSteps)
{
constexpr size_t MaxPathLength = 25;
// Restrict tests to the longest possible path length in vanilla Diablo
constexpr size_t MaxPathLength = 24;
int8_t pathSteps[MaxPathLength];
auto pathLength = FindPath(
/*canStep=*/[](Point, Point) { return true; },
Expand Down Expand Up @@ -153,7 +154,7 @@ TEST(PathTest, LongPaths)
// Starting from the middle of the world and trying to path to a border exceeds the maximum path size
CheckPath({ 56, 56 }, { 0, 0 }, {});

// Longest possible path is currently 24 steps meaning tiles 24 units away are reachable
// Longest possible path used to be 24 steps meaning tiles 24 units away are reachable
Point startingPosition { 56, 56 };
CheckPath(startingPosition, startingPosition + Displacement { 24, 24 }, std::vector<std::string>(24, "↘"));

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