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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef gc_IteratorUtils_h
#define gc_IteratorUtils_h
#include "mozilla/Array.h"
#include "mozilla/Maybe.h"
#include <initializer_list>
namespace js {
/*
* Create an iterator that yields the values from IteratorB(a) for all a in
* IteratorA(). Equivalent to nested for loops over IteratorA and IteratorB
* where IteratorB is constructed with a value from IteratorA.
*/
template <typename IteratorA, typename IteratorB>
class NestedIterator {
using T = decltype(std::declval<IteratorB>().get());
IteratorA a;
mozilla::Maybe<IteratorB> b;
public:
template <typename... Args>
explicit NestedIterator(Args&&... args) : a(std::forward<Args>(args)...) {
settle();
}
bool done() const { return b.isNothing(); }
T get() const {
MOZ_ASSERT(!done());
return b.ref().get();
}
void next() {
MOZ_ASSERT(!done());
b->next();
if (b->done()) {
b.reset();
a.next();
settle();
}
}
const IteratorB& ref() const { return *b; }
operator T() const { return get(); }
T operator->() const { return get(); }
private:
void settle() {
MOZ_ASSERT(b.isNothing());
while (!a.done()) {
b.emplace(a.get());
if (!b->done()) {
break;
}
b.reset();
a.next();
}
}
};
/*
* An iterator the yields values from each of N of instances of Iterator in
* sequence.
*/
template <typename Iterator, size_t N>
class ChainedIterator {
using T = decltype(std::declval<Iterator>().get());
mozilla::Array<Iterator, N> iterators;
size_t index = 0;
public:
template <typename... Args>
MOZ_IMPLICIT ChainedIterator(Args&&... args)
: iterators(Iterator(std::forward<Args>(args))...) {
static_assert(N > 1);
settle();
}
bool done() const { return index == N; }
void next() {
MOZ_ASSERT(!done());
iterators[index].next();
settle();
}
T get() const {
MOZ_ASSERT(!done());
return iterators[index].get();
}
operator T() const { return get(); }
T operator->() const { return get(); }
private:
void settle() {
MOZ_ASSERT(!done());
while (iterators[index].done()) {
index++;
if (done()) {
break;
}
}
}
};
} /* namespace js */
#endif // gc_IteratorUtils_h