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e0d88600e7
The STL supports it only with C++20. Differential Revision: https://phabricator.services.mozilla.com/D97123
129 lines
4.2 KiB
C++
129 lines
4.2 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/* A polyfill for `<algorithm>`. */
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#ifndef mozilla_Algorithm_h
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#define mozilla_Algorithm_h
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#include "mozilla/Result.h"
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#include <iterator>
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#include <type_traits>
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namespace mozilla {
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// Returns true if all elements in the range [aFirst, aLast)
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// satisfy the predicate aPred.
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template <class Iter, class Pred>
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constexpr bool AllOf(Iter aFirst, Iter aLast, Pred aPred) {
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for (; aFirst != aLast; ++aFirst) {
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if (!aPred(*aFirst)) {
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return false;
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}
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}
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return true;
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}
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// Like C++20's `std::any_of`.
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template <typename Iter, typename Pred>
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constexpr bool AnyOf(Iter aFirst, Iter aLast, Pred aPred) {
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for (; aFirst != aLast; ++aFirst) {
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if (aPred(*aFirst)) {
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return true;
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}
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}
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return false;
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}
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namespace detail {
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template <typename Transform, typename SrcIter>
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using ArrayElementTransformType = typename std::invoke_result_t<
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Transform, typename std::iterator_traits<SrcIter>::reference>;
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template <typename Transform, typename SrcIter>
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struct TransformTraits {
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using result_type = ArrayElementTransformType<Transform, SrcIter>;
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using result_ok_type = typename result_type::ok_type;
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using result_err_type = typename result_type::err_type;
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};
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} // namespace detail
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// An algorithm similar to TransformAbortOnErr combined with a condition that
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// allows to skip elements. At most std::distance(aIter, aEnd) elements will be
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// inserted into aDst.
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//
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// Type requirements, in addition to those specified in TransformAbortOnErr:
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// - Cond must be compatible with signature
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// bool (const SrcIter::value_type&)
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template <typename SrcIter, typename DstIter, typename Cond, typename Transform>
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Result<Ok,
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typename detail::TransformTraits<Transform, SrcIter>::result_err_type>
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TransformIfAbortOnErr(SrcIter aIter, SrcIter aEnd, DstIter aDst, Cond aCond,
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Transform aTransform) {
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for (; aIter != aEnd; ++aIter) {
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if (!aCond(static_cast<std::add_const_t<
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typename std::iterator_traits<SrcIter>::value_type>&>(
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*aIter))) {
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continue;
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}
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auto res = aTransform(*aIter);
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if (res.isErr()) {
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return Err(res.unwrapErr());
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}
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*aDst++ = res.unwrap();
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}
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return Ok{};
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}
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template <typename SrcRange, typename DstIter, typename Cond,
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typename Transform>
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auto TransformIfAbortOnErr(SrcRange& aRange, DstIter aDst, Cond aCond,
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Transform aTransform) {
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using std::begin;
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using std::end;
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return TransformIfAbortOnErr(begin(aRange), end(aRange), aDst, aCond,
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aTransform);
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}
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// An algorithm similar to std::transform, adapted to error handling based on
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// mozilla::Result<V, E>. It iterates through the input range [aIter, aEnd) and
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// inserts the result of applying aTransform to each element into aDst, if
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// aTransform returns a success result. On the first error result, iterating is
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// aborted, and the error result is returned as an overall result. If all
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// transformations return a success result, Ok is returned as an overall result.
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//
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// Type requirements:
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// - SrcIter must be an InputIterator.
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// - DstIter must be an OutputIterator.
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// - Transform must be compatible with signature
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// Result<DstIter::value_type, E> (SrcIter::reference)
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template <typename SrcIter, typename DstIter, typename Transform>
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Result<Ok,
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typename detail::TransformTraits<Transform, SrcIter>::result_err_type>
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TransformAbortOnErr(SrcIter aIter, SrcIter aEnd, DstIter aDst,
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Transform aTransform) {
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return TransformIfAbortOnErr(
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aIter, aEnd, aDst, [](const auto&) { return true; }, aTransform);
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}
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template <typename SrcRange, typename DstIter, typename Transform>
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auto TransformAbortOnErr(SrcRange& aRange, DstIter aDst, Transform aTransform) {
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using std::begin;
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using std::end;
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return TransformIfAbortOnErr(
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begin(aRange), end(aRange), aDst, [](const auto&) { return true; },
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aTransform);
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}
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} // namespace mozilla
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#endif // mozilla_Algorithm_h
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