From 7ca42dcf3b430b8d549f541de7277093ad515262 Mon Sep 17 00:00:00 2001
From: DualFroz <me@dualfroz.com>
Date: Wed, 9 Sep 2026 16:30:08 +0200
Subject: [PATCH] feat: add popcount64 and minCorner

---
 core/src/Selection.cpp | 155 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 155 insertions(+)
 create mode 100644 core/src/Selection.cpp

diff --git a/core/src/Selection.cpp b/core/src/Selection.cpp
new file mode 100644
index 0000000..a221f7a
--- /dev/null
+++ b/core/src/Selection.cpp
@@ -0,0 +1,155 @@
+#include "vf/Selection.h"
+
+#include <algorithm>
+#include <deque>
+#include <unordered_set>
+
+namespace vf {
+
+namespace {
+
+constexpr int wandUnboundedReach = 1 << 20;
+
+const Vec3i faceOffsets[6] = {
+    {1, 0, 0}, {-1, 0, 0}, {0, 1, 0}, {0, -1, 0}, {0, 0, 1}, {0, 0, -1},
+};
+
+int popcount64(uint64_t value) {
+    int bits = 0;
+    while (value != 0u) {
+        value &= value - 1u;
+        ++bits;
+    }
+    return bits;
+}
+
+Vec3i minCorner(const Vec3i& a, const Vec3i& b) {
+    return {std::min(a.x, b.x), std::min(a.y, b.y), std::min(a.z, b.z)};
+}
+
+Vec3i maxCorner(const Vec3i& a, const Vec3i& b) {
+    return {std::max(a.x, b.x), std::max(a.y, b.y), std::max(a.z, b.z)};
+}
+
+Vec3i extentOf(const Vec3i& lo, const Vec3i& hi) {
+    return {hi.x - lo.x + 1, hi.y - lo.y + 1, hi.z - lo.z + 1};
+}
+
+} // namespace
+
+SelectionMask::SelectionMask(const Vec3i& minCornerIn, const Vec3i& dims) {
+    if (dims.x <= 0 || dims.y <= 0 || dims.z <= 0) return;
+    corner = minCornerIn;
+    size = dims;
+    words.assign((cellCount() + 63u) / 64u, 0u);
+}
+
+Vec3i SelectionMask::max() const {
+    return {corner.x + size.x - 1, corner.y + size.y - 1, corner.z + size.z - 1};
+}
+
+std::size_t SelectionMask::cellCount() const {
+    return static_cast<std::size_t>(size.x) * static_cast<std::size_t>(size.y) *
+           static_cast<std::size_t>(size.z);
+}
+
+bool SelectionMask::inBounds(const Vec3i& position) const {
+    return position.x >= corner.x && position.x < corner.x + size.x &&
+           position.y >= corner.y && position.y < corner.y + size.y &&
+           position.z >= corner.z && position.z < corner.z + size.z;
+}
+
+std::size_t SelectionMask::indexOf(const Vec3i& position) const {
+    std::size_t localX = static_cast<std::size_t>(position.x - corner.x);
+    std::size_t localY = static_cast<std::size_t>(position.y - corner.y);
+    std::size_t localZ = static_cast<std::size_t>(position.z - corner.z);
+    return (localY * static_cast<std::size_t>(size.z) + localZ) * static_cast<std::size_t>(size.x) +
+           localX;
+}
+
+bool SelectionMask::contains(const Vec3i& position) const {
+    if (!inBounds(position)) return false;
+    std::size_t index = indexOf(position);
+    return (words[index >> 6] >> (index & 63u)) & 1u;
+}
+
+void SelectionMask::add(const Vec3i& position) { setCell(position, true); }
+
+void SelectionMask::remove(const Vec3i& position) { setCell(position, false); }
+
+void SelectionMask::setCell(const Vec3i& position, bool on) {
+    if (!inBounds(position)) return;
+    std::size_t index = indexOf(position);
+    uint64_t bit = uint64_t(1) << (index & 63u);
+    bool was = (words[index >> 6] & bit) != 0u;
+    if (was == on) return;
+    if (on) {
+        words[index >> 6] |= bit;
+        ++setCells;
+    } else {
+        words[index >> 6] &= ~bit;
+        --setCells;
+    }
+}
+
+void SelectionMask::fillAll() {
+    std::size_t total = cellCount();
+    if (total == 0u) return;
+    std::fill(words.begin(), words.end(), ~uint64_t(0));
+    std::size_t tail = total & 63u;
+    if (tail != 0u) words.back() = (uint64_t(1) << tail) - 1u;
+    setCells = total;
+}
+
+void SelectionMask::clearAll() {
+    std::fill(words.begin(), words.end(), uint64_t(0));
+    setCells = 0;
+}
+
+void SelectionMask::recount() {
+    std::size_t total = 0;
+    for (uint64_t word : words) total += static_cast<std::size_t>(popcount64(word));
+    setCells = total;
+}
+
+SelectionMask SelectionMask::unionWith(const SelectionMask& other) const {
+    if (cellCount() == 0u) return other;
+    if (other.cellCount() == 0u) return *this;
+    Vec3i lo = minCorner(corner, other.corner);
+    Vec3i hi = maxCorner(max(), other.max());
+    SelectionMask merged(lo, extentOf(lo, hi));
+    forEach([&](const Vec3i& cell) { merged.add(cell); });
+    other.forEach([&](const Vec3i& cell) { merged.add(cell); });
+    return merged;
+}
+
+SelectionMask SelectionMask::intersectWith(const SelectionMask& other) const {
+    Vec3i lo = maxCorner(corner, other.corner);
+    Vec3i hi = minCorner(max(), other.max());
+    if (cellCount() == 0u || other.cellCount() == 0u) return SelectionMask{};
+    if (hi.x < lo.x || hi.y < lo.y || hi.z < lo.z) return SelectionMask{};
+    SelectionMask shared(lo, extentOf(lo, hi));
+    for (int y = lo.y; y <= hi.y; ++y)
+        for (int z = lo.z; z <= hi.z; ++z)
+            for (int x = lo.x; x <= hi.x; ++x) {
+                Vec3i cell{x, y, z};
+                if (contains(cell) && other.contains(cell)) shared.add(cell);
+            }
+    return shared;
+}
+
+SelectionMask SelectionMask::differenceWith(const SelectionMask& other) const {
+    SelectionMask remainder = *this;
+    other.forEach([&](const Vec3i& cell) { remainder.remove(cell); });
+    return remainder;
+}
+
+SelectionMask SelectionMask::inverted() const {
+    SelectionMask flipped(corner, size);
+    if (flipped.cellCount() == 0u) return flipped;
+    flipped.fillAll();
+    for (std::size_t word = 0; word < words.size(); ++word) flipped.words[word] &= ~words[word];
+    flipped.recount();
+    return flipped;
+}
+