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fhahnfhahn
committedJul 24, 2018
Recommit r334887: [SmallSet] Add SmallSetIterator.
Updated to make sure we properly construct/destroy SetIter if it has a non-trivial ctors/dtors, like in MSVC. llvm-svn: 337818
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llvmorg-21-initllvmorg-7.0.0-rc1
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‎llvm/include/llvm/ADT/SmallSet.h

+115-3
Original file line numberDiff line numberDiff line change
@@ -17,21 +17,120 @@
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#include "llvm/ADT/None.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/iterator.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/type_traits.h"
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#include <cstddef>
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#include <functional>
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#include <set>
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#include <type_traits>
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#include <utility>
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namespace llvm {
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/// SmallSetIterator - This class implements a const_iterator for SmallSet by
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/// delegating to the underlying SmallVector or Set iterators.
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template <typename T, unsigned N, typename C>
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class SmallSetIterator
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: public iterator_facade_base<SmallSetIterator<T, N, C>,
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std::forward_iterator_tag, T> {
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private:
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using SetIterTy = typename std::set<T, C>::const_iterator;
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using VecIterTy = typename SmallVector<T, N>::const_iterator;
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using SelfTy = SmallSetIterator<T, N, C>;
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/// Iterators to the parts of the SmallSet containing the data. They are set
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/// depending on isSmall.
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union {
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SetIterTy SetIter;
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VecIterTy VecIter;
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};
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bool isSmall;
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public:
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SmallSetIterator(SetIterTy SetIter) : SetIter(SetIter), isSmall(false) {}
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SmallSetIterator(VecIterTy VecIter) : VecIter(VecIter), isSmall(true) {}
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// Spell out destructor, copy/move constructor and assignment operators for
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// MSVC STL, where set<T>::const_iterator is not trivially copy constructible.
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~SmallSetIterator() {
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if (isSmall)
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VecIter.~VecIterTy();
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else
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SetIter.~SetIterTy();
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}
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SmallSetIterator(const SmallSetIterator &Other) : isSmall(Other.isSmall) {
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if (isSmall)
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VecIter = Other.VecIter;
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else
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// Use placement new, to make sure SetIter is properly constructed, even
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// if it is not trivially copy-able (e.g. in MSVC).
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new (&SetIter) SetIterTy(Other.SetIter);
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}
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SmallSetIterator(SmallSetIterator &&Other) : isSmall(Other.isSmall) {
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if (isSmall)
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VecIter = std::move(Other.VecIter);
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else
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// Use placement new, to make sure SetIter is properly constructed, even
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// if it is not trivially copy-able (e.g. in MSVC).
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new (&SetIter) SetIterTy(std::move(Other.SetIter));
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}
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SmallSetIterator& operator=(const SmallSetIterator& Other) {
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// Call destructor for SetIter, so it gets properly destroyed if it is
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// not trivially destructible in case we are setting VecIter.
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if (!isSmall)
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SetIter.~SetIterTy();
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isSmall = Other.isSmall;
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if (isSmall)
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VecIter = Other.VecIter;
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else
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new (&SetIter) SetIterTy(Other.SetIter);
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return *this;
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}
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SmallSetIterator& operator=(SmallSetIterator&& Other) {
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// Call destructor for SetIter, so it gets properly destroyed if it is
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// not trivially destructible in case we are setting VecIter.
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if (!isSmall)
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SetIter.~SetIterTy();
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isSmall = Other.isSmall;
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if (isSmall)
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VecIter = std::move(Other.VecIter);
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else
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new (&SetIter) SetIterTy(std::move(Other.SetIter));
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return *this;
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}
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bool operator==(const SmallSetIterator &RHS) const {
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if (isSmall != RHS.isSmall)
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return false;
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if (isSmall)
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return VecIter == RHS.VecIter;
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return SetIter == RHS.SetIter;
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}
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SmallSetIterator &operator++() { // Preincrement
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if (isSmall)
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VecIter++;
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else
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SetIter++;
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return *this;
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}
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const T &operator*() const { return isSmall ? *VecIter : *SetIter; }
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};
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/// SmallSet - This maintains a set of unique values, optimizing for the case
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/// when the set is small (less than N). In this case, the set can be
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/// maintained with no mallocs. If the set gets large, we expand to using an
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/// std::set to maintain reasonable lookup times.
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///
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/// Note that this set does not provide a way to iterate over members in the
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/// set.
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template <typename T, unsigned N, typename C = std::less<T>>
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class SmallSet {
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/// Use a SmallVector to hold the elements here (even though it will never
@@ -50,6 +149,7 @@ class SmallSet {
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public:
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using size_type = size_t;
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using const_iterator = SmallSetIterator<T, N, C>;
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SmallSet() = default;
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@@ -121,6 +221,18 @@ class SmallSet {
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Set.clear();
122222
}
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const_iterator begin() const {
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if (isSmall())
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return {Vector.begin()};
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return {Set.begin()};
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}
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const_iterator end() const {
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if (isSmall())
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return {Vector.end()};
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return {Set.end()};
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}
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private:
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bool isSmall() const { return Set.empty(); }
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‎llvm/unittests/ADT/SmallSetTest.cpp

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@@ -13,6 +13,7 @@
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#include "llvm/ADT/SmallSet.h"
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#include "gtest/gtest.h"
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#include <string>
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using namespace llvm;
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@@ -68,3 +69,81 @@ TEST(SmallSetTest, Erase) {
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EXPECT_EQ(0u, s1.count(8));
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}
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TEST(SmallSetTest, IteratorInt) {
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SmallSet<int, 4> s1;
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// Test the 'small' case.
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for (int i = 0; i < 3; i++)
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s1.insert(i);
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std::vector<int> V(s1.begin(), s1.end());
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// Make sure the elements are in the expected order.
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std::sort(V.begin(), V.end());
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for (int i = 0; i < 3; i++)
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EXPECT_EQ(i, V[i]);
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// Test the 'big' case by adding a few more elements to switch to std::set
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// internally.
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for (int i = 3; i < 6; i++)
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s1.insert(i);
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V.assign(s1.begin(), s1.end());
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// Make sure the elements are in the expected order.
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std::sort(V.begin(), V.end());
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for (int i = 0; i < 6; i++)
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EXPECT_EQ(i, V[i]);
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}
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TEST(SmallSetTest, IteratorString) {
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// Test SmallSetIterator for SmallSet with a type with non-trivial
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// ctors/dtors.
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SmallSet<std::string, 2> s1;
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s1.insert("str 1");
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s1.insert("str 2");
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s1.insert("str 1");
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std::vector<std::string> V(s1.begin(), s1.end());
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std::sort(V.begin(), V.end());
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EXPECT_EQ(2u, s1.size());
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EXPECT_EQ("str 1", V[0]);
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EXPECT_EQ("str 2", V[1]);
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s1.insert("str 4");
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s1.insert("str 0");
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s1.insert("str 4");
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V.assign(s1.begin(), s1.end());
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// Make sure the elements are in the expected order.
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std::sort(V.begin(), V.end());
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EXPECT_EQ(4u, s1.size());
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EXPECT_EQ("str 0", V[0]);
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EXPECT_EQ("str 1", V[1]);
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EXPECT_EQ("str 2", V[2]);
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EXPECT_EQ("str 4", V[3]);
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}
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TEST(SmallSetTest, IteratorIncMoveCopy) {
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// Test SmallSetIterator for SmallSet with a type with non-trivial
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// ctors/dtors.
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SmallSet<std::string, 2> s1;
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s1.insert("str 1");
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s1.insert("str 2");
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auto Iter = s1.begin();
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EXPECT_EQ("str 1", *Iter);
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++Iter;
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EXPECT_EQ("str 2", *Iter);
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s1.insert("str 4");
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s1.insert("str 0");
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auto Iter2 = s1.begin();
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Iter = std::move(Iter2);
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EXPECT_EQ("str 0", *Iter);
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auto Iter3 = s1.end();
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Iter3 = Iter2;
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EXPECT_EQ(Iter3, Iter2);
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}

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