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diff --git a/mfbt/Algorithm.h b/mfbt/Algorithm.h
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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/. */
+
+/* A polyfill for `<algorithm>`. */
+
+#ifndef mozilla_Algorithm_h
+#define mozilla_Algorithm_h
+
+#include "mozilla/Result.h"
+
+#include <iterator>
+#include <type_traits>
+
+namespace mozilla {
+
+// Returns true if all elements in the range [aFirst, aLast)
+// satisfy the predicate aPred.
+template <class Iter, class Pred>
+constexpr bool AllOf(Iter aFirst, Iter aLast, Pred aPred) {
+  for (; aFirst != aLast; ++aFirst) {
+    if (!aPred(*aFirst)) {
+      return false;
+    }
+  }
+  return true;
+}
+
+// Like C++20's `std::any_of`.
+template <typename Iter, typename Pred>
+constexpr bool AnyOf(Iter aFirst, Iter aLast, Pred aPred) {
+  for (; aFirst != aLast; ++aFirst) {
+    if (aPred(*aFirst)) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+namespace detail {
+template <typename Transform, typename SrcIter>
+using ArrayElementTransformType = typename std::invoke_result_t<
+    Transform, typename std::iterator_traits<SrcIter>::reference>;
+
+template <typename Transform, typename SrcIter>
+struct TransformTraits {
+  using result_type = ArrayElementTransformType<Transform, SrcIter>;
+
+  using result_ok_type = typename result_type::ok_type;
+  using result_err_type = typename result_type::err_type;
+};
+}  // namespace detail
+
+// An algorithm similar to TransformAbortOnErr combined with a condition that
+// allows to skip elements. At most std::distance(aIter, aEnd) elements will be
+// inserted into aDst.
+//
+// Type requirements, in addition to those specified in TransformAbortOnErr:
+// - Cond must be compatible with signature
+//   bool (const SrcIter::value_type&)
+template <typename SrcIter, typename DstIter, typename Cond, typename Transform>
+Result<Ok,
+       typename detail::TransformTraits<Transform, SrcIter>::result_err_type>
+TransformIfAbortOnErr(SrcIter aIter, SrcIter aEnd, DstIter aDst, Cond aCond,
+                      Transform aTransform) {
+  for (; aIter != aEnd; ++aIter) {
+    if (!aCond(static_cast<std::add_const_t<
+                   typename std::iterator_traits<SrcIter>::value_type>&>(
+            *aIter))) {
+      continue;
+    }
+
+    auto res = aTransform(*aIter);
+    if (res.isErr()) {
+      return Err(res.unwrapErr());
+    }
+
+    *aDst++ = res.unwrap();
+  }
+  return Ok{};
+}
+
+template <typename SrcRange, typename DstIter, typename Cond,
+          typename Transform>
+auto TransformIfAbortOnErr(SrcRange& aRange, DstIter aDst, Cond aCond,
+                           Transform aTransform) {
+  using std::begin;
+  using std::end;
+  return TransformIfAbortOnErr(begin(aRange), end(aRange), aDst, aCond,
+                               aTransform);
+}
+
+// An algorithm similar to std::transform, adapted to error handling based on
+// mozilla::Result<V, E>. It iterates through the input range [aIter, aEnd) and
+// inserts the result of applying aTransform to each element into aDst, if
+// aTransform returns a success result. On the first error result, iterating is
+// aborted, and the error result is returned as an overall result. If all
+// transformations return a success result, Ok is returned as an overall result.
+//
+// Type requirements:
+// - SrcIter must be an InputIterator.
+// - DstIter must be an OutputIterator.
+// - Transform must be compatible with signature
+//   Result<DstIter::value_type, E> (SrcIter::reference)
+template <typename SrcIter, typename DstIter, typename Transform>
+Result<Ok,
+       typename detail::TransformTraits<Transform, SrcIter>::result_err_type>
+TransformAbortOnErr(SrcIter aIter, SrcIter aEnd, DstIter aDst,
+                    Transform aTransform) {
+  return TransformIfAbortOnErr(
+      aIter, aEnd, aDst, [](const auto&) { return true; }, aTransform);
+}
+
+template <typename SrcRange, typename DstIter, typename Transform>
+auto TransformAbortOnErr(SrcRange& aRange, DstIter aDst, Transform aTransform) {
+  using std::begin;
+  using std::end;
+  return TransformIfAbortOnErr(
+      begin(aRange), end(aRange), aDst, [](const auto&) { return true; },
+      aTransform);
+}
+
+}  // namespace mozilla
+
+#endif  // mozilla_Algorithm_h