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/*
* Copyright 2019 WebAssembly Community Group participants
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
//
// A vector of elements, which may be small, and uses a fixed space
// for those small elements.
//
#ifndef wasm_support_small_vector_h
#define wasm_support_small_vector_h
#include <array>
#include <cassert>
#include <iterator>
#include <vector>
namespace wasm {
template<typename T, size_t N> class SmallVector {
// fixed-space storage
size_t usedFixed = 0;
std::array<T, N> fixed;
// flexible additional storage
std::vector<T> flexible;
public:
using value_type = T;
SmallVector() {}
T& operator[](size_t i) {
return const_cast<T&>(static_cast<const SmallVector<T, N>&>(*this)[i]);
}
const T& operator[](size_t i) const {
if (i < N) {
return fixed[i];
} else {
return flexible[i - N];
}
}
void push_back(const T& x) {
if (usedFixed < N) {
fixed[usedFixed++] = x;
} else {
flexible.push_back(x);
}
}
template<typename... ArgTypes> void emplace_back(ArgTypes&&... Args) {
if (usedFixed < N) {
new (&fixed[usedFixed++]) T(std::forward<ArgTypes>(Args)...);
} else {
flexible.emplace_back(std::forward<ArgTypes>(Args)...);
}
}
void pop_back() {
if (flexible.empty()) {
assert(usedFixed > 0);
usedFixed--;
} else {
flexible.pop_back();
}
}
T& back() {
if (flexible.empty()) {
assert(usedFixed > 0);
return fixed[usedFixed - 1];
} else {
return flexible.back();
}
}
const T& back() const {
if (flexible.empty()) {
assert(usedFixed > 0);
return fixed[usedFixed - 1];
} else {
return flexible.back();
}
}
size_t size() const { return usedFixed + flexible.size(); }
bool empty() const { return size() == 0; }
void clear() {
usedFixed = 0;
flexible.clear();
}
bool operator==(const SmallVector<T, N>& other) const {
if (usedFixed != other.usedFixed) {
return false;
}
for (size_t i = 0; i < usedFixed; i++) {
if (fixed[i] != other.fixed[i]) {
return false;
}
}
return flexible == other.flexible;
}
bool operator!=(const SmallVector<T, N>& other) const {
return !(*this == other);
}
// iteration
struct Iterator {
typedef T value_type;
typedef long difference_type;
typedef T& reference;
const SmallVector<T, N>* parent;
size_t index;
Iterator(const SmallVector<T, N>* parent, size_t index)
: parent(parent), index(index) {}
bool operator!=(const Iterator& other) const {
return index != other.index || parent != other.parent;
}
void operator++() { index++; }
Iterator& operator+=(difference_type off) {
index += off;
return *this;
}
const Iterator operator+(difference_type off) const {
return Iterator(*this) += off;
}
const value_type operator*() const { return (*parent)[index]; }
};
Iterator begin() const {
return Iterator(static_cast<const SmallVector<T, N>*>(this), 0);
}
Iterator end() const {
return Iterator(static_cast<const SmallVector<T, N>*>(this), size());
}
};
} // namespace wasm
#endif // wasm_support_small_vector_h
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