//===- llvm/ADT/TinyPtrVector.h - 'Normally tiny' vectors -------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ADT_TINYPTRVECTOR_H
#define LLVM_ADT_TINYPTRVECTOR_H
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/PointerUnion.h"
#include "llvm/ADT/SmallVector.h"
#include <cassert>
#include <cstddef>
#include <iterator>
#include <type_traits>
namespace llvm {
/// TinyPtrVector - This class is specialized for cases where there are
/// normally 0 or 1 element in a vector, but is general enough to go beyond that
/// when required.
///
/// NOTE: This container doesn't allow you to store a null pointer into it.
///
template <typename EltTy>
class TinyPtrVector {
public:
using VecTy = SmallVector<EltTy, 4>;
using value_type = typename VecTy::value_type;
// EltTy must be the first pointer type so that is<EltTy> is true for the
// default-constructed PtrUnion. This allows an empty TinyPtrVector to
// naturally vend a begin/end iterator of type EltTy* without an additional
// check for the empty state.
using PtrUnion = PointerUnion<EltTy, VecTy *>;
private:
PtrUnion Val;
public:
TinyPtrVector() = default;
~TinyPtrVector() {
if (VecTy *V = Val.template dyn_cast<VecTy*>())
delete V;
}
TinyPtrVector(const TinyPtrVector &RHS) : Val(RHS.Val) {
if (VecTy *V = Val.template dyn_cast<VecTy*>())
Val = new VecTy(*V);
}
TinyPtrVector &operator=(const TinyPtrVector &RHS) {
if (this == &RHS)
return *this;
if (RHS.empty()) {
this->clear();
return *this;
}
// Try to squeeze into the single slot. If it won't fit, allocate a copied
// vector.
if (Val.template is<EltTy>()) {
if (RHS.size() == 1)
Val = RHS.front();
else
Val = new VecTy(*RHS.Val.template get<VecTy*>());
return *this;
}
// If we have a full vector allocated, try to re-use it.
if (RHS.Val.template is<EltTy>()) {
Val.template get<VecTy*>()->clear();
Val.template get<VecTy*>()->push_back(RHS.front());
} else {
*Val.template get<VecTy*>() = *RHS.Val.template get<VecTy*>();
}
return *this;
}
TinyPtrVector(TinyPtrVector &&RHS) : Val(RHS.Val) {
RHS.Val = (EltTy)nullptr;
}
TinyPtrVector &operator=(TinyPtrVector &&RHS) {
if (this == &RHS)
return *this;
if (RHS.empty()) {
this->clear();
return *this;
}
// If this vector has been allocated on the heap, re-use it if cheap. If it
// would require more copying, just delete it and we'll steal the other
// side.
if (VecTy *V = Val.template dyn_cast<VecTy*>()) {
if (RHS.Val.template is<EltTy>()) {
V->clear();
V->push_back(RHS.front());
RHS.Val = EltTy();
return *this;
}
delete V;
}
Val = RHS.Val;
RHS.Val = EltTy();
return *this;
}
TinyPtrVector(std::initializer_list<EltTy> IL)
: Val(IL.size() == 0
? PtrUnion()
: IL.size() == 1 ? PtrUnion(*IL.begin())
: PtrUnion(new VecTy(IL.begin(), IL.end()))) {}
/// Constructor from an ArrayRef.
///
/// This also is a constructor for individual array elements due to the single
/// element constructor for ArrayRef.
explicit TinyPtrVector(ArrayRef<EltTy> Elts)
: Val(Elts.empty()
? PtrUnion()
: Elts.size() == 1
? PtrUnion(Elts[0])
: PtrUnion(new VecTy(Elts.begin(), Elts.end()))) {}
TinyPtrVector(size_t Count, EltTy Value)
: Val(Count == 0 ? PtrUnion()
: Count == 1 ? PtrUnion(Value)
: PtrUnion(new VecTy(Count, Value))) {}
// implicit conversion operator to ArrayRef.
operator ArrayRef<EltTy>() const {
if (Val.isNull())
return std::nullopt;
if (Val.template is<EltTy>())
return *Val.getAddrOfPtr1();
return *Val.template get<VecTy*>();
}
// implicit conversion operator to MutableArrayRef.
operator MutableArrayRef<EltTy>() {
if (Val.isNull())
return std::nullopt;
if (Val.template is<EltTy>())
return *Val.getAddrOfPtr1();
return *Val.template get<VecTy*>();
}
// Implicit conversion to ArrayRef<U> if EltTy* implicitly converts to U*.
template <
typename U,
std::enable_if_t<std::is_convertible<ArrayRef<EltTy>, ArrayRef<U>>::value,
bool> = false>
operator ArrayRef<U>() const {
return operator ArrayRef<EltTy>();
}
bool empty() const {
// This vector can be empty if it contains no element, or if it
// contains a pointer to an empty vector.
if (Val.isNull()) return true;
if (VecTy *Vec = Val.template dyn_cast<VecTy*>())
return Vec->empty();
return false;
}
unsigned size() const {
if (empty())
return 0;
if (Val.template is<EltTy>())
return 1;
return Val.template get<VecTy*>()->size();
}
using iterator = EltTy *;
using const_iterator = const EltTy *;
using reverse_iterator = std::reverse_iterator<iterator>;
using const_reverse_iterator = std::reverse_iterator<const_iterator>;
iterator begin() {
if (Val.template is<EltTy>())
return Val.getAddrOfPtr1();
return Val.template get<VecTy *>()->begin();
}
iterator end() {
if (Val.template is<EltTy>())
return begin() + (Val.isNull() ? 0 : 1);
return Val.template get<VecTy *>()->end();
}
const_iterator begin() const {
return (const_iterator)const_cast<TinyPtrVector*>(this)->begin();
}
const_iterator end() const {
return (const_iterator)const_cast<TinyPtrVector*>(this)->end();
}
reverse_iterator rbegin() { return reverse_iterator(end()); }
reverse_iterator rend() { return reverse_iterator(begin()); }
const_reverse_iterator rbegin() const {
return const_reverse_iterator(end());
}
const_reverse_iterator rend() const {
return const_reverse_iterator(begin());
}
EltTy operator[](unsigned i) const {
assert(!Val.isNull() && "can't index into an empty vector");
if (Val.template is<EltTy>()) {
assert(i == 0 && "tinyvector index out of range");
return Val.template get<EltTy>();
}
assert(i < Val.template get<VecTy*>()->size() &&
"tinyvector index out of range");
return (*Val.template get<VecTy*>())[i];
}
EltTy front() const {
assert(!empty() && "vector empty");
if (Val.template is<EltTy>())
return Val.template get<EltTy>();
return Val.template get<VecTy*>()->front();
}
EltTy back() const {
assert(!empty() && "vector empty");
if (Val.template is<EltTy>())
return Val.template get<EltTy>();
return Val.template get<VecTy*>()->back();
}
void push_back(EltTy NewVal) {
// If we have nothing, add something.
if (Val.isNull()) {
Val = NewVal;
assert(!Val.isNull() && "Can't add a null value");
return;
}
// If we have a single value, convert to a vector.
if (Val.template is<EltTy>()) {
EltTy V = Val.template get<EltTy>();
Val = new VecTy();
Val.template get<VecTy*>()->push_back(V);
}
// Add the new value, we know we have a vector.
Val.template get<VecTy*>()->push_back(NewVal);
}
void pop_back() {
// If we have a single value, convert to empty.
if (Val.template is<EltTy>())
Val = (EltTy)nullptr;
else if (VecTy *Vec = Val.template get<VecTy*>())
Vec->pop_back();
}
void clear() {
// If we have a single value, convert to empty.
if (Val.template is<EltTy>()) {
Val = EltTy();
} else if (VecTy *Vec = Val.template dyn_cast<VecTy*>()) {
// If we have a vector form, just clear it.
Vec->clear();
}
// Otherwise, we're already empty.
}
iterator erase(iterator I) {
assert(I >= begin() && "Iterator to erase is out of bounds.");
assert(I < end() && "Erasing at past-the-end iterator.");
// If we have a single value, convert to empty.
if (Val.template is<EltTy>()) {
if (I == begin())
Val = EltTy();
} else if (VecTy *Vec = Val.template dyn_cast<VecTy*>()) {
// multiple items in a vector; just do the erase, there is no
// benefit to collapsing back to a pointer
return Vec->erase(I);
}
return end();
}
iterator erase(iterator S, iterator E) {
assert(S >= begin() && "Range to erase is out of bounds.");
assert(S <= E && "Trying to erase invalid range.");
assert(E <= end() && "Trying to erase past the end.");
if (Val.template is<EltTy>()) {
if (S == begin() && S != E)
Val = EltTy();
} else if (VecTy *Vec = Val.template dyn_cast<VecTy*>()) {
return Vec->erase(S, E);
}
return end();
}
iterator insert(iterator I, const EltTy &Elt) {
assert(I >= this->begin() && "Insertion iterator is out of bounds.");
assert(I <= this->end() && "Inserting past the end of the vector.");
if (I == end()) {
push_back(Elt);
return std::prev(end());
}
assert(!Val.isNull() && "Null value with non-end insert iterator.");
if (Val.template is<EltTy>()) {
EltTy V = Val.template get<EltTy>();
assert(I == begin());
Val = Elt;
push_back(V);
return begin();
}
return Val.template get<VecTy*>()->insert(I, Elt);
}
template<typename ItTy>
iterator insert(iterator I, ItTy From, ItTy To) {
assert(I >= this->begin() && "Insertion iterator is out of bounds.");
assert(I <= this->end() && "Inserting past the end of the vector.");
if (From == To)
return I;
// If we have a single value, convert to a vector.
ptrdiff_t Offset = I - begin();
if (Val.isNull()) {
if (std::next(From) == To) {
Val = *From;
return begin();
}
Val = new VecTy();
} else if (Val.template is<EltTy>()) {
EltTy V = Val.template get<EltTy>();
Val = new VecTy();
Val.template get<VecTy*>()->push_back(V);
}
return Val.template get<VecTy*>()->insert(begin() + Offset, From, To);
}
};
} // end namespace llvm
#endif // LLVM_ADT_TINYPTRVECTOR_H