source/blender/blenkernel/BKE_bvhutils.h

@@ -108,7 +108,7 @@ BVHTree *bvhtree_from_editmesh_verts(
  */
 BVHTree *bvhtree_from_editmesh_verts_ex(BVHTreeFromEditMesh *data,
                                         struct BMEditMesh *em,
-                                        const blender::BitVector<> &mask,
+                                        blender::BitSpan mask,
                                         int verts_num_active,
                                         float epsilon,
                                         int tree_type,
@@ -124,7 +124,7 @@ BVHTree *bvhtree_from_editmesh_verts_ex(BVHTreeFromEditMesh *data,
 BVHTree *bvhtree_from_mesh_verts_ex(struct BVHTreeFromMesh *data,
                                     const float (*vert_positions)[3],
                                     int verts_num,
-                                    const blender::BitVector<> &verts_mask,
+                                    blender::BitSpan verts_mask,
                                     int verts_num_active,
                                     float epsilon,
                                     int tree_type,
@@ -138,7 +138,7 @@ BVHTree *bvhtree_from_editmesh_edges(
  */
 BVHTree *bvhtree_from_editmesh_edges_ex(BVHTreeFromEditMesh *data,
                                         struct BMEditMesh *em,
-                                        const blender::BitVector<> &edges_mask,
+                                        blender::BitSpan edges_mask,
                                         int edges_num_active,
                                         float epsilon,
                                         int tree_type,
@@ -156,7 +156,7 @@ BVHTree *bvhtree_from_mesh_edges_ex(struct BVHTreeFromMesh *data,
                                     const float (*vert_positions)[3],
                                     const struct MEdge *edge,
                                     int edges_num,
-                                    const blender::BitVector<> &edges_mask,
+                                    blender::BitSpan edges_mask,
                                     int edges_num_active,
                                     float epsilon,
                                     int tree_type,
@@ -170,7 +170,7 @@ BVHTree *bvhtree_from_editmesh_looptri(
  */
 BVHTree *bvhtree_from_editmesh_looptri_ex(BVHTreeFromEditMesh *data,
                                           struct BMEditMesh *em,
-                                          const blender::BitVector<> &mask,
+                                          blender::BitSpan mask,
                                           int looptri_num_active,
                                           float epsilon,
                                           int tree_type,
@@ -184,7 +184,7 @@ BVHTree *bvhtree_from_mesh_looptri_ex(struct BVHTreeFromMesh *data,
                                       const struct MLoop *mloop,
                                       const struct MLoopTri *looptri,
                                       int looptri_num,
-                                      const blender::BitVector<> &mask,
+                                      blender::BitSpan mask,
                                       int looptri_num_active,
                                       float epsilon,
                                       int tree_type,

source/blender/blenkernel/intern/bvhutils.cc

@@ -29,6 +29,7 @@
 
 #include "MEM_guardedalloc.h"
 
+using blender::BitSpan;
 using blender::BitVector;
 using blender::float3;
 using blender::IndexRange;
@@ -672,7 +673,7 @@ static BVHTree *bvhtree_from_editmesh_verts_create_tree(float epsilon,
                                                         int tree_type,
                                                         int axis,
                                                         BMEditMesh *em,
-                                                        const BitVector<> &verts_mask,
+                                                        const BitSpan verts_mask,
                                                         int verts_num_active)
 {
   BM_mesh_elem_table_ensure(em->bm, BM_VERT);
@@ -706,7 +707,7 @@ static BVHTree *bvhtree_from_mesh_verts_create_tree(float epsilon,
                                                     int axis,
                                                     const float (*positions)[3],
                                                     const int verts_num,
-                                                    const BitVector<> &verts_mask,
+                                                    const BitSpan verts_mask,
                                                     int verts_num_active)
 {
   if (!verts_mask.is_empty()) {
@@ -737,7 +738,7 @@ static BVHTree *bvhtree_from_mesh_verts_create_tree(float epsilon,
 
 BVHTree *bvhtree_from_editmesh_verts_ex(BVHTreeFromEditMesh *data,
                                         BMEditMesh *em,
-                                        const BitVector<> &verts_mask,
+                                        const BitSpan verts_mask,
                                         int verts_num_active,
                                         float epsilon,
                                         int tree_type,
@@ -764,7 +765,7 @@ BVHTree *bvhtree_from_editmesh_verts(
 BVHTree *bvhtree_from_mesh_verts_ex(BVHTreeFromMesh *data,
                                     const float (*vert_positions)[3],
                                     const int verts_num,
-                                    const BitVector<> &verts_mask,
+                                    const BitSpan verts_mask,
                                     int verts_num_active,
                                     float epsilon,
                                     int tree_type,
@@ -794,7 +795,7 @@ static BVHTree *bvhtree_from_editmesh_edges_create_tree(float epsilon,
                                                         int tree_type,
                                                         int axis,
                                                         BMEditMesh *em,
-                                                        const BitVector<> &edges_mask,
+                                                        const BitSpan edges_mask,
                                                         int edges_num_active)
 {
   BM_mesh_elem_table_ensure(em->bm, BM_EDGE);
@@ -833,7 +834,7 @@ static BVHTree *bvhtree_from_editmesh_edges_create_tree(float epsilon,
 static BVHTree *bvhtree_from_mesh_edges_create_tree(const float (*positions)[3],
                                                     const MEdge *edge,
                                                     const int edge_num,
-                                                    const BitVector<> &edges_mask,
+                                                    const BitSpan edges_mask,
                                                     int edges_num_active,
                                                     float epsilon,
                                                     int tree_type,
@@ -871,7 +872,7 @@ static BVHTree *bvhtree_from_mesh_edges_create_tree(const float (*positions)[3],
 
 BVHTree *bvhtree_from_editmesh_edges_ex(BVHTreeFromEditMesh *data,
                                         BMEditMesh *em,
-                                        const BitVector<> &edges_mask,
+                                        const BitSpan edges_mask,
                                         int edges_num_active,
                                         float epsilon,
                                         int tree_type,
@@ -899,7 +900,7 @@ BVHTree *bvhtree_from_mesh_edges_ex(BVHTreeFromMesh *data,
                                     const float (*vert_positions)[3],
                                     const MEdge *edge,
                                     const int edges_num,
-                                    const BitVector<> &edges_mask,
+                                    const BitSpan edges_mask,
                                     int edges_num_active,
                                     float epsilon,
                                     int tree_type,
@@ -931,7 +932,7 @@ static BVHTree *bvhtree_from_mesh_faces_create_tree(float epsilon,
                                                     const float (*positions)[3],
                                                     const MFace *face,
                                                     const int faces_num,
-                                                    const BitVector<> &faces_mask,
+                                                    const BitSpan faces_mask,
                                                     int faces_num_active)
 {
   if (faces_num == 0) {
@@ -984,7 +985,7 @@ static BVHTree *bvhtree_from_editmesh_looptri_create_tree(float epsilon,
                                                           int tree_type,
                                                           int axis,
                                                           BMEditMesh *em,
-                                                          const BitVector<> &looptri_mask,
+                                                          const BitSpan looptri_mask,
                                                           int looptri_num_active)
 {
   const int looptri_num = em->tottri;
@@ -1038,7 +1039,7 @@ static BVHTree *bvhtree_from_mesh_looptri_create_tree(float epsilon,
                                                       const MLoop *mloop,
                                                       const MLoopTri *looptri,
                                                       const int looptri_num,
-                                                      const BitVector<> &looptri_mask,
+                                                      const BitSpan looptri_mask,
                                                       int looptri_num_active)
 {
   if (!looptri_mask.is_empty()) {
@@ -1079,7 +1080,7 @@ static BVHTree *bvhtree_from_mesh_looptri_create_tree(float epsilon,
 
 BVHTree *bvhtree_from_editmesh_looptri_ex(BVHTreeFromEditMesh *data,
                                           BMEditMesh *em,
-                                          const BitVector<> &looptri_mask,
+                                          const BitSpan looptri_mask,
                                           int looptri_num_active,
                                           float epsilon,
                                           int tree_type,
@@ -1109,7 +1110,7 @@ BVHTree *bvhtree_from_mesh_looptri_ex(BVHTreeFromMesh *data,
                                       const struct MLoop *mloop,
                                       const struct MLoopTri *looptri,
                                       const int looptri_num,
-                                      const BitVector<> &looptri_mask,
+                                      const BitSpan looptri_mask,
                                       int looptri_num_active,
                                       float epsilon,
                                       int tree_type,

source/blender/blenkernel/intern/mesh.cc

@@ -17,7 +17,6 @@
 #include "DNA_meshdata_types.h"
 #include "DNA_object_types.h"
 
-#include "BLI_bit_vector.hh"
 #include "BLI_bounds.hh"
 #include "BLI_edgehash.h"
 #include "BLI_endian_switch.h"
@@ -66,7 +65,6 @@
 
 #include "BLO_read_write.h"
 
-using blender::BitVector;
 using blender::float3;
 using blender::MutableSpan;
 using blender::Span;

source/blender/blenkernel/intern/mesh_iterators.cc

@@ -316,7 +316,7 @@ void BKE_mesh_foreach_mapped_subdiv_face_center(
                                       BKE_mesh_vertex_normals_ensure(mesh) :
                                       nullptr;
   const int *index = static_cast<const int *>(CustomData_get_layer(&mesh->pdata, CD_ORIGINDEX));
-  const blender::BitVector<> &facedot_tags = mesh->runtime->subsurf_face_dot_tags;
+  const blender::BitSpan facedot_tags = mesh->runtime->subsurf_face_dot_tags;
 
   if (index) {
     for (int i = 0; i < mesh->totpoly; i++, mp++) {

source/blender/blenkernel/intern/mesh_normals.cc

@@ -42,6 +42,7 @@
 using blender::BitVector;
 using blender::float3;
 using blender::int2;
+using blender::MutableBitSpan;
 using blender::MutableSpan;
 using blender::short2;
 using blender::Span;
@@ -1238,7 +1239,7 @@ static bool loop_split_generator_check_cyclic_smooth_fan(const Span<MLoop> mloop
                                                          const Span<int2> edge_to_loops,
                                                          const Span<int> loop_to_poly,
                                                          const int *e2l_prev,
-                                                         BitVector<> &skip_loops,
+                                                         MutableBitSpan skip_loops,
                                                          const int ml_curr_index,
                                                          const int ml_prev_index,
                                                          const int mp_curr_index)

source/blender/blenlib/BLI_bit_ref.hh

@@ -0,0 +1,234 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#pragma once
+
+/** \file
+ * \ingroup bli
+ *
+ * This file provides the basis for processing "indexed bits" (i.e. every bit has an index).
+ * The main purpose of this file is to define how bits are indexed within a memory buffer.
+ * For example, one has to define whether the first bit is the least or most significant bit and
+ * how endianness affect the bit order.
+ *
+ * The order is defined as follows:
+ * - Every indexed bit is part of an #BitInt. These ints are ordered by their address as usual.
+ * - Within each #BitInt, the bits are ordered from least to most significant.
+ */
+
+#include "BLI_index_range.hh"
+#include "BLI_utildefines.h"
+
+#include <ostream>
+
+namespace blender::bits {
+
+/** Using a large integer type is better because then it's easier to process many bits at once. */
+using BitInt = uint64_t;
+/** Number of bits that fit into #BitInt. */
+static constexpr int64_t BitsPerInt = int64_t(sizeof(BitInt) * 8);
+/** Shift amount to get from a bit index to an int index. Equivalent to `log(BitsPerInt, 2)`. */
+static constexpr int64_t BitToIntIndexShift = 3 + (sizeof(BitInt) >= 2) + (sizeof(BitInt) >= 4) +
+                                              (sizeof(BitInt) >= 8);
+/** Bit mask containing a 1 for the last few bits that index a bit inside of an #BitInt. */
+static constexpr BitInt BitIndexMask = (BitInt(1) << BitToIntIndexShift) - 1;
+
+inline BitInt mask_first_n_bits(const int64_t n)
+{
+  BLI_assert(n >= 0);
+  BLI_assert(n <= BitsPerInt);
+  if (n == BitsPerInt) {
+    return BitInt(-1);
+  }
+  return (BitInt(1) << n) - 1;
+}
+
+inline BitInt mask_last_n_bits(const int64_t n)
+{
+  return ~mask_first_n_bits(BitsPerInt - n);
+}
+
+inline BitInt mask_range_bits(const int64_t start, const int64_t size)
+{
+  BLI_assert(start >= 0);
+  BLI_assert(size >= 0);
+  const int64_t end = start + size;
+  BLI_assert(end <= BitsPerInt);
+  if (end == BitsPerInt) {
+    return mask_last_n_bits(size);
+  }
+  return ((BitInt(1) << end) - 1) & ~((BitInt(1) << start) - 1);
+}
+
+inline BitInt mask_single_bit(const int64_t bit_index)
+{
+  BLI_assert(bit_index >= 0);
+  BLI_assert(bit_index < BitsPerInt);
+  return BitInt(1) << bit_index;
+}
+
+inline BitInt *int_containing_bit(BitInt *data, const int64_t bit_index)
+{
+  return data + (bit_index >> BitToIntIndexShift);
+}
+
+inline const BitInt *int_containing_bit(const BitInt *data, const int64_t bit_index)
+{
+  return data + (bit_index >> BitToIntIndexShift);
+}
+
+/**
+ * This is a read-only pointer to a specific bit. The value of the bit can be retrieved, but
+ * not changed.
+ */
+class BitRef {
+ private:
+  /** Points to the exact integer that the bit is in. */
+  const BitInt *int_;
+  /** All zeros except for a single one at the bit that is referenced. */
+  BitInt mask_;
+
+  friend class MutableBitRef;
+
+ public:
+  BitRef() = default;
+
+  /**
+   * Reference a specific bit in an array. Note that #data does *not* have to point to the
+   * exact integer the bit is in.
+   */
+  BitRef(const BitInt *data, const int64_t bit_index)
+  {
+    int_ = int_containing_bit(data, bit_index);
+    mask_ = mask_single_bit(bit_index & BitIndexMask);
+  }
+
+  /**
+   * Return true when the bit is currently 1 and false otherwise.
+   */
+  bool test() const
+  {
+    const BitInt value = *int_;
+    const BitInt masked_value = value & mask_;
+    return masked_value != 0;
+  }
+
+  operator bool() const
+  {
+    return this->test();
+  }
+};
+
+/**
+ * Similar to #BitRef, but also allows changing the referenced bit.
+ */
+class MutableBitRef {
+ private:
+  /** Points to the integer that the bit is in. */
+  BitInt *int_;
+  /** All zeros except for a single one at the bit that is referenced. */
+  BitInt mask_;
+
+ public:
+  MutableBitRef() = default;
+
+  /**
+   * Reference a specific bit in an array. Note that #data does *not* have to point to the
+   * exact int the bit is in.
+   */
+  MutableBitRef(BitInt *data, const int64_t bit_index)
+  {
+    int_ = int_containing_bit(data, bit_index);
+    mask_ = mask_single_bit(bit_index & BitIndexMask);
+  }
+
+  /**
+   * Support implicitly casting to a read-only #BitRef.
+   */
+  operator BitRef() const
+  {
+    BitRef bit_ref;
+    bit_ref.int_ = int_;
+    bit_ref.mask_ = mask_;
+    return bit_ref;
+  }
+
+  /**
+   * Return true when the bit is currently 1 and false otherwise.
+   */
+  bool test() const
+  {
+    const BitInt value = *int_;
+    const BitInt masked_value = value & mask_;
+    return masked_value != 0;
+  }
+
+  operator bool() const
+  {
+    return this->test();
+  }
+
+  /**
+   * Change the bit to a 1.
+   */
+  void set()
+  {
+    *int_ |= mask_;
+  }
+
+  /**
+   * Change the bit to a 0.
+   */
+  void reset()
+  {
+    *int_ &= ~mask_;
+  }
+
+  /**
+   * Change the bit to a 1 if #value is true and 0 otherwise. If the value is highly unpredictable
+   * by the CPU branch predictor, it can be faster to use #set_branchless instead.
+   */
+  void set(const bool value)
+  {
+    if (value) {
+      this->set();
+    }
+    else {
+      this->reset();
+    }
+  }
+
+  /**
+   * Does the same as #set, but does not use a branch. This is faster when the input value is
+   * unpredictable for the CPU branch predictor (best case for this function is a uniform random
+   * distribution with 50% probability for true and false). If the value is predictable, this is
+   * likely slower than #set.
+   */
+  void set_branchless(const bool value)
+  {
+    const BitInt value_int = BitInt(value);
+    BLI_assert(ELEM(value_int, 0, 1));
+    const BitInt old = *int_;
+    *int_ =
+        /* Unset bit. */
+        (~mask_ & old)
+        /* Optionally set it again. The -1 turns a 1 into `0x00...` and a 0 into `0xff...`. */
+        | (mask_ & ~(value_int - 1));
+  }
+};
+
+inline std::ostream &operator<<(std::ostream &stream, const BitRef &bit)
+{
+  return stream << (bit ? "1" : "0");
+}
+
+inline std::ostream &operator<<(std::ostream &stream, const MutableBitRef &bit)
+{
+  return stream << BitRef(bit);
+}
+
+}  // namespace blender::bits
+
+namespace blender {
+using bits::BitRef;
+using bits::MutableBitRef;
+}  // namespace blender

source/blender/blenlib/BLI_bit_span.hh

@@ -0,0 +1,290 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#pragma once
+
+#include "BLI_bit_ref.hh"
+#include "BLI_index_range.hh"
+#include "BLI_memory_utils.hh"
+
+namespace blender::bits {
+
+/** Base class for a const and non-const bit-iterator. */
+class BitIteratorBase {
+ protected:
+  const BitInt *data_;
+  int64_t bit_index_;
+
+ public:
+  BitIteratorBase(const BitInt *data, const int64_t bit_index) : data_(data), bit_index_(bit_index)
+  {
+  }
+
+  BitIteratorBase &operator++()
+  {
+    bit_index_++;
+    return *this;
+  }
+
+  friend bool operator!=(const BitIteratorBase &a, const BitIteratorBase &b)
+  {
+    BLI_assert(a.data_ == b.data_);
+    return a.bit_index_ != b.bit_index_;
+  }
+};
+
+/** Allows iterating over the bits in a memory buffer. */
+class BitIterator : public BitIteratorBase {
+ public:
+  BitIterator(const BitInt *data, const int64_t bit_index) : BitIteratorBase(data, bit_index)
+  {
+  }
+
+  BitRef operator*() const
+  {
+    return BitRef(data_, bit_index_);
+  }
+};
+
+/** Allows iterating over the bits in a memory buffer. */
+class MutableBitIterator : public BitIteratorBase {
+ public:
+  MutableBitIterator(BitInt *data, const int64_t bit_index) : BitIteratorBase(data, bit_index)
+  {
+  }
+
+  MutableBitRef operator*() const
+  {
+    return MutableBitRef(const_cast<BitInt *>(data_), bit_index_);
+  }
+};
+
+/**
+ * Similar to #Span, but references a range of bits instead of normal C++ types (which must be at
+ * least one byte large). Use #MutableBitSpan if the values are supposed to be modified.
+ *
+ * The beginning and end of a #BitSpan does *not* have to be at byte/int boundaries. It can start
+ * and end at any bit.
+ */
+class BitSpan {
+ private:
+  /** Base pointer to the integers containing the bits. The actual bit span might start at a much
+   * higher address when `bit_range_.start()` is large. */
+  const BitInt *data_ = nullptr;
+  /** The range of referenced bits. */
+  IndexRange bit_range_ = {0, 0};
+
+ public:
+  /** Construct an empty span. */
+  BitSpan() = default;
+
+  BitSpan(const BitInt *data, const int64_t size_in_bits) : data_(data), bit_range_(size_in_bits)
+  {
+  }
+
+  BitSpan(const BitInt *data, const IndexRange bit_range) : data_(data), bit_range_(bit_range)
+  {
+  }
+
+  /** Number of bits referenced by the span. */
+  int64_t size() const
+  {
+    return bit_range_.size();
+  }
+
+  bool is_empty() const
+  {
+    return bit_range_.is_empty();
+  }
+
+  IndexRange index_range() const
+  {
+    return IndexRange(bit_range_.size());
+  }
+
+  BitRef operator[](const int64_t index) const
+  {
+    BLI_assert(index >= 0);
+    BLI_assert(index < bit_range_.size());
+    return {data_, bit_range_.start() + index};
+  }
+
+  BitSpan slice(const IndexRange range) const
+  {
+    return {data_, bit_range_.slice(range)};
+  }
+
+  const BitInt *data() const
+  {
+    return data_;
+  }
+
+  const IndexRange &bit_range() const
+  {
+    return bit_range_;
+  }
+
+  BitIterator begin() const
+  {
+    return {data_, bit_range_.start()};
+  }
+
+  BitIterator end() const
+  {
+    return {data_, bit_range_.one_after_last()};
+  }
+};
+
+/** Same as #BitSpan, but also allows modifying the referenced bits. */
+class MutableBitSpan {
+ private:
+  BitInt *data_ = nullptr;
+  IndexRange bit_range_ = {0, 0};
+
+ public:
+  MutableBitSpan() = default;
+
+  MutableBitSpan(BitInt *data, const int64_t size) : data_(data), bit_range_(size)
+  {
+  }
+
+  MutableBitSpan(BitInt *data, const IndexRange bit_range) : data_(data), bit_range_(bit_range)
+  {
+  }
+
+  int64_t size() const
+  {
+    return bit_range_.size();
+  }
+
+  bool is_empty() const
+  {
+    return bit_range_.is_empty();
+  }
+
+  IndexRange index_range() const
+  {
+    return IndexRange(bit_range_.size());
+  }
+
+  MutableBitRef operator[](const int64_t index) const
+  {
+    BLI_assert(index >= 0);
+    BLI_assert(index < bit_range_.size());
+    return {data_, bit_range_.start() + index};
+  }
+
+  MutableBitSpan slice(const IndexRange range) const
+  {
+    return {data_, bit_range_.slice(range)};
+  }
+
+  BitInt *data() const
+  {
+    return data_;
+  }
+
+  const IndexRange &bit_range() const
+  {
+    return bit_range_;
+  }
+
+  MutableBitIterator begin() const
+  {
+    return {data_, bit_range_.start()};
+  }
+
+  MutableBitIterator end() const
+  {
+    return {data_, bit_range_.one_after_last()};
+  }
+
+  operator BitSpan() const
+  {
+    return {data_, bit_range_};
+  }
+
+  /** Sets all referenced bits to 1. */
+  void set_all()
+  {
+    const AlignedIndexRanges ranges = split_index_range_by_alignment(bit_range_, BitsPerInt);
+    {
+      BitInt &first_int = *int_containing_bit(data_, bit_range_.start());
+      const BitInt first_int_mask = mask_range_bits(ranges.prefix.start() & BitIndexMask,
+                                                    ranges.prefix.size());
+      first_int |= first_int_mask;
+    }
+    {
+      BitInt *start = int_containing_bit(data_, ranges.aligned.start());
+      const int64_t ints_to_fill = ranges.aligned.size() / BitsPerInt;
+      constexpr BitInt fill_value = BitInt(-1);
+      initialized_fill_n(start, ints_to_fill, fill_value);
+    }
+    {
+      BitInt &last_int = *int_containing_bit(data_, bit_range_.one_after_last() - 1);
+      const BitInt last_int_mask = mask_first_n_bits(ranges.suffix.size());
+      last_int |= last_int_mask;
+    }
+  }
+
+  /** Sets all referenced bits to 0. */
+  void reset_all()
+  {
+    const AlignedIndexRanges ranges = split_index_range_by_alignment(bit_range_, BitsPerInt);
+    {
+      BitInt &first_int = *int_containing_bit(data_, bit_range_.start());
+      const BitInt first_int_mask = mask_range_bits(ranges.prefix.start() & BitIndexMask,
+                                                    ranges.prefix.size());
+      first_int &= ~first_int_mask;
+    }
+    {
+      BitInt *start = int_containing_bit(data_, ranges.aligned.start());
+      const int64_t ints_to_fill = ranges.aligned.size() / BitsPerInt;
+      constexpr BitInt fill_value = 0;
+      initialized_fill_n(start, ints_to_fill, fill_value);
+    }
+    {
+      BitInt &last_int = *int_containing_bit(data_, bit_range_.one_after_last() - 1);
+      const BitInt last_int_mask = mask_first_n_bits(ranges.suffix.size());
+      last_int &= ~last_int_mask;
+    }
+  }
+
+  /** Sets all referenced bits to either 0 or 1. */
+  void set_all(const bool value)
+  {
+    if (value) {
+      this->set_all();
+    }
+    else {
+      this->reset_all();
+    }
+  }
+
+  /** Same as #set_all to mirror #MutableSpan. */
+  void fill(const bool value)
+  {
+    this->set_all(value);
+  }
+};
+
+inline std::ostream &operator<<(std::ostream &stream, const BitSpan &span)
+{
+  stream << "(Size: " << span.size() << ", ";
+  for (const BitRef bit : span) {
+    stream << bit;
+  }
+  stream << ")";
+  return stream;
+}
+
+inline std::ostream &operator<<(std::ostream &stream, const MutableBitSpan &span)
+{
+  return stream << BitSpan(span);
+}
+
+}  // namespace blender::bits
+
+namespace blender {
+using bits::BitSpan;
+using bits::MutableBitSpan;
+}  // namespace blender

source/blender/blenlib/BLI_bit_vector.hh

@@ -38,142 +38,11 @@
 #include <cstring>
 
 #include "BLI_allocator.hh"
-#include "BLI_index_range.hh"
+#include "BLI_bit_span.hh"
-#include "BLI_memory_utils.hh"
 #include "BLI_span.hh"
 
 namespace blender::bits {
 
-/**
- * Using a large integer type is better because then it's easier to process many bits at once.
- */
-using IntType = uint64_t;
-static constexpr int64_t BitsPerInt = int64_t(sizeof(IntType) * 8);
-static constexpr int64_t BitToIntIndexShift = 3 + (sizeof(IntType) >= 2) + (sizeof(IntType) >= 4) +
-                                              (sizeof(IntType) >= 8);
-static constexpr IntType BitIndexMask = (IntType(1) << BitToIntIndexShift) - 1;
-
-/**
- * This is a read-only pointer to a specific bit. The value of the bit can be retrieved, but
- * not changed.
- */
-class BitRef {
- private:
-  /** Points to the integer that the bit is in. */
-  const IntType *ptr_;
-  /** All zeros except for a single one at the bit that is referenced. */
-  IntType mask_;
-
-  friend class MutableBitRef;
-
- public:
-  BitRef() = default;
-
-  /**
-   * Reference a specific bit in an array. Note that #ptr does *not* have to point to the
-   * exact integer the bit is in.
-   */
-  BitRef(const IntType *ptr, const int64_t bit_index)
-  {
-    ptr_ = ptr + (bit_index >> BitToIntIndexShift);
-    mask_ = IntType(1) << (bit_index & BitIndexMask);
-  }
-
-  /**
-   * Return true when the bit is currently 1 and false otherwise.
-   */
-  bool test() const
-  {
-    const IntType value = *ptr_;
-    const IntType masked_value = value & mask_;
-    return masked_value != 0;
-  }
-
-  operator bool() const
-  {
-    return this->test();
-  }
-};
-
-/**
- * Similar to #BitRef, but also allows changing the referenced bit.
- */
-class MutableBitRef {
- private:
-  /** Points to the integer that the bit is in. */
-  IntType *ptr_;
-  /** All zeros except for a single one at the bit that is referenced. */
-  IntType mask_;
-
- public:
-  MutableBitRef() = default;
-
-  /**
-   * Reference a specific bit in an array. Note that #ptr does *not* have to point to the
-   * exact int the bit is in.
-   */
-  MutableBitRef(IntType *ptr, const int64_t bit_index)
-  {
-    ptr_ = ptr + (bit_index >> BitToIntIndexShift);
-    mask_ = IntType(1) << IntType(bit_index & BitIndexMask);
-  }
-
-  /**
-   * Support implicitly casting to a read-only #BitRef.
-   */
-  operator BitRef() const
-  {
-    BitRef bit_ref;
-    bit_ref.ptr_ = ptr_;
-    bit_ref.mask_ = mask_;
-    return bit_ref;
-  }
-
-  /**
-   * Return true when the bit is currently 1 and false otherwise.
-   */
-  bool test() const
-  {
-    const IntType value = *ptr_;
-    const IntType masked_value = value & mask_;
-    return masked_value != 0;
-  }
-
-  operator bool() const
-  {
-    return this->test();
-  }
-
-  /**
-   * Change the bit to a 1.
-   */
-  void set()
-  {
-    *ptr_ |= mask_;
-  }
-
-  /**
-   * Change the bit to a 0.
-   */
-  void reset()
-  {
-    *ptr_ &= ~mask_;
-  }
-
-  /**
-   * Change the bit to a 1 if #value is true and 0 otherwise.
-   */
-  void set(const bool value)
-  {
-    if (value) {
-      this->set();
-    }
-    else {
-      this->reset();
-    }
-  }
-};
-
 template<
     /**
      * Number of bits that can be stored in the vector without doing an allocation.
@@ -193,13 +62,13 @@ class BitVector {
 
   static constexpr int64_t IntsInInlineBuffer = required_ints_for_bits(InlineBufferCapacity);
   static constexpr int64_t BitsInInlineBuffer = IntsInInlineBuffer * BitsPerInt;
-  static constexpr int64_t AllocationAlignment = alignof(IntType);
+  static constexpr int64_t AllocationAlignment = alignof(BitInt);
 
   /**
    * Points to the first integer used by the vector. It might point to the memory in the inline
    * buffer.
    */
-  IntType *data_;
+  BitInt *data_;
 
   /** Current size of the vector in bits. */
   int64_t size_in_bits_;
@@ -211,7 +80,7 @@ class BitVector {
   BLI_NO_UNIQUE_ADDRESS Allocator allocator_;
 
   /** Contains the bits as long as the vector is small enough. */
-  BLI_NO_UNIQUE_ADDRESS TypedBuffer<IntType, IntsInInlineBuffer> inline_buffer_;
+  BLI_NO_UNIQUE_ADDRESS TypedBuffer<BitInt, IntsInInlineBuffer> inline_buffer_;
 
  public:
   BitVector(Allocator allocator = {}) noexcept : allocator_(allocator)
@@ -219,7 +88,7 @@ class BitVector {
     data_ = inline_buffer_;
     size_in_bits_ = 0;
     capacity_in_bits_ = BitsInInlineBuffer;
-    uninitialized_fill_n(data_, IntsInInlineBuffer, IntType(0));
+    uninitialized_fill_n(data_, IntsInInlineBuffer, BitInt(0));
   }
 
   BitVector(NoExceptConstructor, Allocator allocator = {}) noexcept : BitVector(allocator)
@@ -236,8 +105,8 @@ class BitVector {
     }
     else {
       /* Allocate a new array because the inline buffer is too small. */
-      data_ = static_cast<IntType *>(
+      data_ = static_cast<BitInt *>(
-          allocator_.allocate(ints_to_copy * sizeof(IntType), AllocationAlignment, __func__));
+          allocator_.allocate(ints_to_copy * sizeof(BitInt), AllocationAlignment, __func__));
       capacity_in_bits_ = ints_to_copy * BitsPerInt;
     }
     size_in_bits_ = other.size_in_bits_;
@@ -303,6 +172,16 @@ class BitVector {
     return move_assign_container(*this, std::move(other));
   }
 
+  operator BitSpan() const
+  {
+    return {data_, IndexRange(size_in_bits_)};
+  }
+
+  operator MutableBitSpan()
+  {
+    return {data_, IndexRange(size_in_bits_)};
+  }
+
   /**
    * Number of bits in the bit vector.
    */
@@ -352,80 +231,24 @@ class BitVector {
     size_in_bits_++;
   }
 
-  class Iterator {
+  BitIterator begin() const
-   private:
-    const BitVector *vector_;
-    int64_t index_;
-
-   public:
-    Iterator(const BitVector &vector, const int64_t index) : vector_(&vector), index_(index)
   {
+    return {data_, 0};
   }
 
-    Iterator &operator++()
+  BitIterator end() const
   {
-      index_++;
+    return {data_, size_in_bits_};
-      return *this;
   }
 
-    friend bool operator!=(const Iterator &a, const Iterator &b)
+  MutableBitIterator begin()
   {
-      BLI_assert(a.vector_ == b.vector_);
+    return {data_, 0};
-      return a.index_ != b.index_;
   }
 
-    BitRef operator*() const
+  MutableBitIterator end()
   {
-      return (*vector_)[index_];
+    return {data_, size_in_bits_};
-    }
-  };
-
-  class MutableIterator {
-   private:
-    BitVector *vector_;
-    int64_t index_;
-
-   public:
-    MutableIterator(BitVector &vector, const int64_t index) : vector_(&vector), index_(index)
-    {
-    }
-
-    MutableIterator &operator++()
-    {
-      index_++;
-      return *this;
-    }
-
-    friend bool operator!=(const MutableIterator &a, const MutableIterator &b)
-    {
-      BLI_assert(a.vector_ == b.vector_);
-      return a.index_ != b.index_;
-    }
-
-    MutableBitRef operator*() const
-    {
-      return (*vector_)[index_];
-    }
-  };
-
-  Iterator begin() const
-  {
-    return {*this, 0};
-  }
-
-  Iterator end() const
-  {
-    return {*this, size_in_bits_};
-  }
-
-  MutableIterator begin()
-  {
-    return {*this, 0};
-  }
-
-  MutableIterator end()
-  {
-    return {*this, size_in_bits_};
   }
 
   /**
@@ -441,31 +264,8 @@ class BitVector {
     }
     size_in_bits_ = new_size_in_bits;
     if (old_size_in_bits < new_size_in_bits) {
-      this->fill_range(IndexRange(old_size_in_bits, new_size_in_bits - old_size_in_bits), value);
+      MutableBitSpan(data_, IndexRange(old_size_in_bits, new_size_in_bits - old_size_in_bits))
-    }
+          .set_all(value);
-  }
-
-  /**
-   * Set #value for every element in #range.
-   */
-  void fill_range(const IndexRange range, const bool value)
-  {
-    const AlignedIndexRanges aligned_ranges = split_index_range_by_alignment(range, BitsPerInt);
-
-    /* Fill first few bits. */
-    for (const int64_t i : aligned_ranges.prefix) {
-      (*this)[i].set(value);
-    }
-
-    /* Fill entire ints at once. */
-    const int64_t start_fill_int_index = aligned_ranges.aligned.start() / BitsPerInt;
-    const int64_t ints_to_fill = aligned_ranges.aligned.size() / BitsPerInt;
-    const IntType fill_value = value ? IntType(-1) : IntType(0);
-    initialized_fill_n(data_ + start_fill_int_index, ints_to_fill, fill_value);
-
-    /* Fill bits in the end that don't cover a full int. */
-    for (const int64_t i : aligned_ranges.suffix) {
-      (*this)[i].set(value);
     }
   }
 
@@ -474,7 +274,7 @@ class BitVector {
    */
   void fill(const bool value)
   {
-    this->fill_range(IndexRange(0, size_in_bits_), value);
+    MutableBitSpan(data_, size_in_bits_).set_all(value);
   }
 
   /**
@@ -517,7 +317,7 @@ class BitVector {
   }
 
   BLI_NOINLINE void realloc_to_at_least(const int64_t min_capacity_in_bits,
-                                        const IntType initial_value_for_new_ints = 0x00)
+                                        const BitInt initial_value_for_new_ints = 0)
   {
     if (capacity_in_bits_ >= min_capacity_in_bits) {
       return;
@@ -531,8 +331,8 @@ class BitVector {
     const int64_t new_capacity_in_ints = std::max(min_capacity_in_ints, min_new_capacity_in_ints);
     const int64_t ints_to_copy = this->used_ints_amount();
 
-    IntType *new_data = static_cast<IntType *>(allocator_.allocate(
+    BitInt *new_data = static_cast<BitInt *>(
-        new_capacity_in_ints * sizeof(IntType), AllocationAlignment, __func__));
+        allocator_.allocate(new_capacity_in_ints * sizeof(BitInt), AllocationAlignment, __func__));
     uninitialized_copy_n(data_, ints_to_copy, new_data);
     /* Always initialize new capacity even if it isn't used yet. That's necessary to avoid warnings
      * caused by using uninitialized memory. This happens when e.g. setting a clearing a bit in an
@@ -562,7 +362,5 @@ class BitVector {
 }  // namespace blender::bits
 
 namespace blender {
-using bits::BitRef;
 using bits::BitVector;
-using bits::MutableBitRef;
 }  // namespace blender

source/blender/blenlib/CMakeLists.txt

@@ -457,6 +457,8 @@ if(WITH_GTESTS)
     tests/BLI_array_store_test.cc
     tests/BLI_array_test.cc
     tests/BLI_array_utils_test.cc
+    tests/BLI_bit_ref_test.cc
+    tests/BLI_bit_span_test.cc
     tests/BLI_bit_vector_test.cc
     tests/BLI_bitmap_test.cc
     tests/BLI_bounds_test.cc

source/blender/blenlib/tests/BLI_bit_ref_test.cc

@@ -0,0 +1,160 @@
+/* SPDX-License-Identifier: Apache-2.0 */
+
+#include <array>
+
+#include "BLI_bit_ref.hh"
+
+#include "testing/testing.h"
+
+namespace blender::bits::tests {
+
+TEST(bit_ref, MaskFirstNBits)
+{
+  EXPECT_EQ(mask_first_n_bits(0), 0);
+  EXPECT_EQ(mask_first_n_bits(1),
+            0b0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0001);
+  EXPECT_EQ(mask_first_n_bits(5),
+            0b0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0001'1111);
+  EXPECT_EQ(mask_first_n_bits(63),
+            0b0111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111);
+  EXPECT_EQ(mask_first_n_bits(64),
+            0b1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111);
+}
+
+TEST(bit_ref, MaskLastNBits)
+{
+  EXPECT_EQ(mask_last_n_bits(0),
+            0b0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000);
+  EXPECT_EQ(mask_last_n_bits(1),
+            0b1000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000);
+  EXPECT_EQ(mask_last_n_bits(5),
+            0b1111'1000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000);
+  EXPECT_EQ(mask_last_n_bits(63),
+            0b1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1110);
+  EXPECT_EQ(mask_last_n_bits(64),
+            0b1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111);
+}
+
+TEST(bit_ref, MaskSingleBit)
+{
+  EXPECT_EQ(mask_single_bit(0), 1);
+  EXPECT_EQ(mask_single_bit(1),
+            0b0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0010);
+  EXPECT_EQ(mask_single_bit(5),
+            0b0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0010'0000);
+  EXPECT_EQ(mask_single_bit(63),
+            0b1000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000);
+}
+
+TEST(bit_ref, IntContainingBit)
+{
+  std::array<uint64_t, 5> array;
+  uint64_t *data = array.data();
+  EXPECT_EQ(int_containing_bit(data, 0), data);
+  EXPECT_EQ(int_containing_bit(data, 1), data);
+  EXPECT_EQ(int_containing_bit(data, 63), data);
+  EXPECT_EQ(int_containing_bit(data, 64), data + 1);
+  EXPECT_EQ(int_containing_bit(data, 65), data + 1);
+  EXPECT_EQ(int_containing_bit(data, 100), data + 1);
+  EXPECT_EQ(int_containing_bit(data, 127), data + 1);
+  EXPECT_EQ(int_containing_bit(data, 128), data + 2);
+  const uint64_t *data_const = data;
+  EXPECT_EQ(int_containing_bit(data_const, 0), data_const);
+  EXPECT_EQ(int_containing_bit(data_const, 1), data_const);
+  EXPECT_EQ(int_containing_bit(data_const, 63), data_const);
+  EXPECT_EQ(int_containing_bit(data_const, 64), data_const + 1);
+  EXPECT_EQ(int_containing_bit(data_const, 65), data_const + 1);
+  EXPECT_EQ(int_containing_bit(data_const, 100), data_const + 1);
+  EXPECT_EQ(int_containing_bit(data_const, 127), data_const + 1);
+  EXPECT_EQ(int_containing_bit(data_const, 128), data_const + 2);
+}
+
+TEST(bit_ref, Test)
+{
+  uint64_t data = (1 << 3) | (1 << 7);
+  EXPECT_FALSE(BitRef(&data, 0).test());
+  EXPECT_FALSE(BitRef(&data, 1).test());
+  EXPECT_FALSE(BitRef(&data, 2).test());
+  EXPECT_TRUE(BitRef(&data, 3).test());
+  EXPECT_FALSE(BitRef(&data, 4));
+  EXPECT_FALSE(BitRef(&data, 5));
+  EXPECT_FALSE(BitRef(&data, 6));
+  EXPECT_TRUE(BitRef(&data, 7));
+
+  EXPECT_FALSE(MutableBitRef(&data, 0).test());
+  EXPECT_FALSE(MutableBitRef(&data, 1).test());
+  EXPECT_FALSE(MutableBitRef(&data, 2).test());
+  EXPECT_TRUE(MutableBitRef(&data, 3).test());
+  EXPECT_FALSE(MutableBitRef(&data, 4));
+  EXPECT_FALSE(MutableBitRef(&data, 5));
+  EXPECT_FALSE(MutableBitRef(&data, 6));
+  EXPECT_TRUE(MutableBitRef(&data, 7));
+}
+
+TEST(bit_ref, Set)
+{
+  uint64_t data = 0;
+  MutableBitRef(&data, 0).set();
+  MutableBitRef(&data, 1).set();
+  MutableBitRef(&data, 1).set();
+  MutableBitRef(&data, 4).set();
+  EXPECT_EQ(data, (1 << 0) | (1 << 1) | (1 << 4));
+  MutableBitRef(&data, 5).set(true);
+  MutableBitRef(&data, 1).set(false);
+  EXPECT_EQ(data, (1 << 0) | (1 << 4) | (1 << 5));
+}
+
+TEST(bit_ref, Reset)
+{
+  uint64_t data = -1;
+  MutableBitRef(&data, 0).reset();
+  MutableBitRef(&data, 2).reset();
+  EXPECT_EQ(data, uint64_t(-1) & ~(1 << 0) & ~(1 << 2));
+}
+
+TEST(bit_ref, SetBranchless)
+{
+  uint64_t data = 0;
+  MutableBitRef(&data, 0).set_branchless(true);
+  EXPECT_EQ(data, 1);
+  MutableBitRef(&data, 0).set_branchless(false);
+  EXPECT_EQ(data, 0);
+  MutableBitRef(&data, 3).set_branchless(false);
+  MutableBitRef(&data, 4).set_branchless(true);
+  EXPECT_EQ(data, 16);
+  MutableBitRef(&data, 3).set_branchless(true);
+  MutableBitRef(&data, 4).set_branchless(true);
+  EXPECT_EQ(data, 24);
+}
+
+TEST(bit_ref, Cast)
+{
+  uint64_t data = 0;
+  MutableBitRef mutable_ref(&data, 3);
+  BitRef ref = mutable_ref;
+  EXPECT_FALSE(ref);
+  mutable_ref.set();
+  EXPECT_TRUE(ref);
+}
+
+TEST(bit_ref, MaskRangeBits)
+{
+  EXPECT_EQ(mask_range_bits(0, 0),
+            0b0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000);
+  EXPECT_EQ(mask_range_bits(0, 1),
+            0b0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0001);
+  EXPECT_EQ(mask_range_bits(0, 5),
+            0b0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0001'1111);
+  EXPECT_EQ(mask_range_bits(64, 0),
+            0b0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000);
+  EXPECT_EQ(mask_range_bits(63, 1),
+            0b1000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000);
+  EXPECT_EQ(mask_range_bits(59, 5),
+            0b1111'1000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000);
+  EXPECT_EQ(mask_range_bits(8, 3),
+            0b0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0111'0000'0000);
+  EXPECT_EQ(mask_range_bits(0, 64),
+            0b1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111'1111);
+}
+
+}  // namespace blender::bits::tests

source/blender/blenlib/tests/BLI_bit_span_test.cc

@@ -0,0 +1,139 @@
+/* SPDX-License-Identifier: Apache-2.0 */
+
+#include <array>
+
+#include "BLI_bit_span.hh"
+
+#include "testing/testing.h"
+
+namespace blender::bits::tests {
+
+TEST(bit_span, DefaultConstructor)
+{
+  {
+    char buffer[sizeof(BitSpan)];
+    memset(buffer, 0xff, sizeof(BitSpan));
+    BitSpan &span = *new (buffer) BitSpan();
+    EXPECT_TRUE(span.is_empty());
+    EXPECT_EQ(span.size(), 0);
+  }
+  {
+    char buffer[sizeof(MutableBitSpan)];
+    memset(buffer, 0xff, sizeof(MutableBitSpan));
+    MutableBitSpan &span = *new (buffer) MutableBitSpan();
+    EXPECT_TRUE(span.is_empty());
+    EXPECT_EQ(span.size(), 0);
+  }
+}
+
+TEST(bit_span, Iteration)
+{
+  uint64_t data = (1 << 2) | (1 << 3);
+  const BitSpan span(&data, 30);
+  EXPECT_EQ(span.size(), 30);
+  int index = 0;
+  for (const BitRef bit : span) {
+    EXPECT_EQ(bit.test(), ELEM(index, 2, 3));
+    index++;
+  }
+}
+
+TEST(bit_span, MutableIteration)
+{
+  uint64_t data = 0;
+  MutableBitSpan span(&data, 40);
+  EXPECT_EQ(span.size(), 40);
+  int index = 0;
+  for (MutableBitRef bit : span) {
+    bit.set(index % 4 == 0);
+    index++;
+  }
+  EXPECT_EQ(data,
+            0b0000'0000'0000'0000'0000'0000'0001'0001'0001'0001'0001'0001'0001'0001'0001'0001);
+}
+
+TEST(bit_span, SubscriptOperator)
+{
+  uint64_t data[2] = {0, 0};
+  MutableBitSpan mutable_span(data, 128);
+  BitSpan span = mutable_span;
+
+  EXPECT_EQ(mutable_span.data(), data);
+  EXPECT_EQ(mutable_span.bit_range(), IndexRange(128));
+  EXPECT_EQ(span.data(), data);
+  EXPECT_EQ(span.bit_range(), IndexRange(128));
+
+  EXPECT_FALSE(mutable_span[5].test());
+  EXPECT_FALSE(span[5].test());
+  mutable_span[5].set(5);
+  EXPECT_TRUE(mutable_span[5].test());
+  EXPECT_TRUE(span[5].test());
+
+  EXPECT_FALSE(mutable_span[120].test());
+  EXPECT_FALSE(span[120].test());
+  mutable_span[120].set(120);
+  EXPECT_TRUE(mutable_span[120].test());
+  EXPECT_TRUE(span[120].test());
+
+  EXPECT_EQ(data[0],
+            0b0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0010'0000);
+  EXPECT_EQ(data[1],
+            0b0000'0001'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000);
+}
+
+TEST(bit_span, RangeConstructor)
+{
+  uint64_t data = 0;
+  MutableBitSpan mutable_span(&data, IndexRange(4, 3));
+  BitSpan span = mutable_span;
+
+  EXPECT_FALSE(mutable_span[1].test());
+  EXPECT_FALSE(span[1].test());
+  mutable_span[0].set(true);
+  mutable_span[1].set(true);
+  mutable_span[2].set(true);
+  mutable_span[0].set(false);
+  mutable_span[2].set(false);
+  EXPECT_TRUE(mutable_span[1].test());
+  EXPECT_TRUE(span[1].test());
+
+  EXPECT_EQ(data,
+            0b0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0010'0000);
+}
+
+TEST(bit_span, Set)
+{
+  uint64_t data = 0;
+  MutableBitSpan(&data, 64).set_all(true);
+  EXPECT_EQ(data, uint64_t(-1));
+  MutableBitSpan(&data, 64).set_all(false);
+  EXPECT_EQ(data, uint64_t(0));
+
+  MutableBitSpan(&data, IndexRange(4, 8)).set_all(true);
+  EXPECT_EQ(data,
+            0b0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'1111'1111'0000);
+  MutableBitSpan(&data, IndexRange(8, 30)).set_all(false);
+
+  EXPECT_EQ(data,
+            0b0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'0000'1111'0000);
+}
+
+TEST(bit_span, SetSliced)
+{
+  std::array<uint64_t, 10> data;
+  memset(data.data(), 0, sizeof(data));
+  MutableBitSpan span{data.data(), 640};
+  span.slice(IndexRange(5, 500)).set_all(true);
+
+  for (const int64_t i : IndexRange(640)) {
+    EXPECT_EQ(span[i], i >= 5 && i < 505);
+  }
+
+  span.slice(IndexRange(10, 190)).set_all(false);
+
+  for (const int64_t i : IndexRange(640)) {
+    EXPECT_EQ(span[i], (i >= 5 && i < 10) || (i >= 200 && i < 505));
+  }
+}
+
+}  // namespace blender::bits::tests

source/blender/blenlib/tests/BLI_bit_vector_test.cc

@@ -6,7 +6,7 @@
 
 #include "testing/testing.h"
 
-namespace blender::tests {
+namespace blender::bits::tests {
 
 TEST(bit_vector, DefaultConstructor)
 {
@@ -183,4 +183,4 @@ TEST(bit_vector, AppendMany)
   EXPECT_TRUE(vec[5]);
 }
 
-}  // namespace blender::tests
+}  // namespace blender::bits::tests

source/blender/blenlib/tests/BLI_index_range_test.cc

@@ -290,6 +290,24 @@ TEST(index_range, SplitByAlignment)
     EXPECT_EQ(ranges.aligned, IndexRange());
     EXPECT_EQ(ranges.suffix, IndexRange());
   }
+  {
+    AlignedIndexRanges ranges = split_index_range_by_alignment(IndexRange(64), 64);
+    EXPECT_EQ(ranges.prefix, IndexRange());
+    EXPECT_EQ(ranges.aligned, IndexRange(64));
+    EXPECT_EQ(ranges.suffix, IndexRange());
+  }
+  {
+    AlignedIndexRanges ranges = split_index_range_by_alignment(IndexRange(64, 64), 64);
+    EXPECT_EQ(ranges.prefix, IndexRange());
+    EXPECT_EQ(ranges.aligned, IndexRange(64, 64));
+    EXPECT_EQ(ranges.suffix, IndexRange());
+  }
+  {
+    AlignedIndexRanges ranges = split_index_range_by_alignment(IndexRange(4, 8), 64);
+    EXPECT_EQ(ranges.prefix, IndexRange(4, 8));
+    EXPECT_EQ(ranges.aligned, IndexRange());
+    EXPECT_EQ(ranges.suffix, IndexRange());
+  }
 }
 
 }  // namespace blender::tests

source/blender/bmesh/intern/bmesh_iterators.cc

@@ -211,7 +211,7 @@ void *BMO_iter_as_arrayN(BMOpSlot slot_args[BMO_OP_MAX_SLOTS],
 
 int BM_iter_mesh_bitmap_from_filter(const char itype,
                                     BMesh *bm,
-                                    blender::BitVector<> &bitmap,
+                                    blender::MutableBitSpan bitmap,
                                     bool (*test_fn)(BMElem *, void *user_data),
                                     void *user_data)
 {
@@ -234,7 +234,7 @@ int BM_iter_mesh_bitmap_from_filter(const char itype,
 }
 
 int BM_iter_mesh_bitmap_from_filter_tessface(BMesh *bm,
-                                             blender::BitVector<> &bitmap,
+                                             blender::MutableBitSpan bitmap,
                                              bool (*test_fn)(BMFace *, void *user_data),
                                              void *user_data)
 {

source/blender/bmesh/intern/bmesh_iterators.h

@@ -21,7 +21,7 @@
 #include "BLI_mempool.h"
 
 #ifdef __cplusplus
-#  include "BLI_bit_vector.hh"
+#  include "BLI_bit_span.hh"
 #endif
 
 #ifdef __cplusplus
@@ -228,14 +228,14 @@ void *BMO_iter_as_arrayN(BMOpSlot slot_args[BMO_OP_MAX_SLOTS],
 
 int BM_iter_mesh_bitmap_from_filter(char itype,
                                     BMesh *bm,
-                                    blender::BitVector<> &bitmap,
+                                    blender::MutableBitSpan bitmap,
                                     bool (*test_fn)(BMElem *, void *user_data),
                                     void *user_data);
 /**
  * Needed when we want to check faces, but return a loop aligned array.
  */
 int BM_iter_mesh_bitmap_from_filter_tessface(BMesh *bm,
-                                             blender::BitVector<> &bitmap,
+                                             blender::MutableBitSpan bitmap,
                                              bool (*test_fn)(BMFace *, void *user_data),
                                              void *user_data);
 

source/blender/draw/intern/mesh_extractors/extract_mesh_ibo_edituv.cc

@@ -557,7 +557,7 @@ static void extract_edituv_fdots_iter_poly_mesh(const MeshRenderData *mr,
   const bool mp_select = (efa) ? BM_elem_flag_test_bool(efa, BM_ELEM_SELECT) : false;
 
   if (mr->use_subsurf_fdots) {
-    const BitVector<> &facedot_tags = mr->me->runtime->subsurf_face_dot_tags;
+    const BitSpan facedot_tags = mr->me->runtime->subsurf_face_dot_tags;
 
     const MLoop *mloop = mr->mloop;
     const int ml_index_end = mp->loopstart + mp->totloop;

source/blender/draw/intern/mesh_extractors/extract_mesh_ibo_fdots.cc

@@ -46,7 +46,7 @@ static void extract_fdots_iter_poly_mesh(const MeshRenderData *mr,
 
   GPUIndexBufBuilder *elb = static_cast<GPUIndexBufBuilder *>(_userdata);
   if (mr->use_subsurf_fdots) {
-    const BitVector<> &facedot_tags = mr->me->runtime->subsurf_face_dot_tags;
+    const BitSpan facedot_tags = mr->me->runtime->subsurf_face_dot_tags;
 
     const MLoop *mloop = mr->mloop;
     const int ml_index_end = mp->loopstart + mp->totloop;

source/blender/draw/intern/mesh_extractors/extract_mesh_vbo_edge_fac.cc

@@ -102,7 +102,7 @@ static void extract_edge_fac_iter_poly_mesh(const MeshRenderData *mr,
                                             void *_data)
 {
   MeshExtract_EdgeFac_Data *data = static_cast<MeshExtract_EdgeFac_Data *>(_data);
-  const BitVector<> &optimal_display_edges = mr->me->runtime->subsurf_optimal_display_edges;
+  const BitSpan optimal_display_edges = mr->me->runtime->subsurf_optimal_display_edges;
 
   const MLoop *mloop = mr->mloop;
   const int ml_index_end = mp->loopstart + mp->totloop;

source/blender/draw/intern/mesh_extractors/extract_mesh_vbo_fdots_pos.cc

@@ -76,7 +76,7 @@ static void extract_fdots_pos_iter_poly_mesh(const MeshRenderData *mr,
   zero_v3(co);
 
   const MLoop *mloop = mr->mloop;
-  const BitVector<> &facedot_tags = mr->me->runtime->subsurf_face_dot_tags;
+  const BitSpan facedot_tags = mr->me->runtime->subsurf_face_dot_tags;
 
   const int ml_index_end = mp->loopstart + mp->totloop;
   for (int ml_index = mp->loopstart; ml_index < ml_index_end; ml_index += 1) {

source/blender/draw/intern/mesh_extractors/extract_mesh_vbo_fdots_uv.cc

@@ -74,7 +74,7 @@ static void extract_fdots_uv_iter_poly_mesh(const MeshRenderData *mr,
                                             void *_data)
 {
   MeshExtract_FdotUV_Data *data = static_cast<MeshExtract_FdotUV_Data *>(_data);
-  const BitVector<> &facedot_tags = mr->me->runtime->subsurf_face_dot_tags;
+  const BitSpan facedot_tags = mr->me->runtime->subsurf_face_dot_tags;
 
   const MLoop *mloop = mr->mloop;
   const int ml_index_end = mp->loopstart + mp->totloop;