Update immer library to current master (0a718d2d76bab6ebdcf43de943bd6c7d2dbfe2f9) (#2821)

* Update immer library to current master (0a718d2d76bab6ebdcf43de943bd6c7d2dbfe2f9)

* Temporary fix for alignof(std::max_align_t) on MinGW 32bit builds

See arximboldi/immer#78

Author: codablock

src/immer/array.hpp

@@ -35,10 +35,6 @@ class array_transient;
  *    of doubt, measure.  For basic types, using an `array` when
  *    :math:`n < 100` is a good heuristic.
  *
- * .. warning:: The current implementation depends on
- *    ``boost::intrusive_ptr`` and does not support :doc:`memory
- *    policies<memory>`.  This will be fixed soon.
- *
  * @endrst
  */
 template <typename T, typename MemoryPolicy = default_memory_policy>
@@ -73,23 +69,26 @@ class array
     array() = default;
 
     /*!
-     * Constructs a vector containing the elements in `values`.
+     * Constructs an array containing the elements in `values`.
      */
     array(std::initializer_list<T> values)
         : impl_{impl_t::from_initializer_list(values)}
     {}
 
     /*!
-     * Constructs a vector containing the elements in the range
-     * defined by the input iterators `first` and `last`.
+     * Constructs a array containing the elements in the range
+     * defined by the forward iterator `first` and range sentinel `last`.
      */
-    template <typename Iter>
-    array(Iter first, Iter last)
+    template <typename Iter, typename Sent,
+              std::enable_if_t
+              <detail::compatible_sentinel_v<Iter, Sent>
+               && detail::is_forward_iterator_v<Iter>, bool> = true>
+    array(Iter first, Sent last)
         : impl_{impl_t::from_range(first, last)}
     {}
 
     /*!
-     * Constructs a vector containing the element `val` repeated `n`
+     * Constructs a array containing the element `val` repeated `n`
      * times.
      */
     array(size_type n, T v = {})

src/immer/atom.hpp

@@ -0,0 +1,259 @@
+//
+// immer: immutable data structures for C++
+// Copyright (C) 2016, 2017, 2018 Juan Pedro Bolivar Puente
+//
+// This software is distributed under the Boost Software License, Version 1.0.
+// See accompanying file LICENSE or copy at http://boost.org/LICENSE_1_0.txt
+//
+
+#pragma once
+
+#include <immer/box.hpp>
+#include <immer/refcount/no_refcount_policy.hpp>
+
+#include <atomic>
+#include <type_traits>
+
+namespace immer {
+
+namespace detail {
+
+template <typename T, typename MemoryPolicy>
+struct refcount_atom_impl
+{
+    using box_type = box<T, MemoryPolicy>;
+    using value_type = T;
+    using memory_policy = MemoryPolicy;
+    using spinlock_t = typename MemoryPolicy::refcount::spinlock_type;
+    using scoped_lock_t = typename spinlock_t::scoped_lock;
+
+    refcount_atom_impl(const refcount_atom_impl&) = delete;
+    refcount_atom_impl(refcount_atom_impl&&) = delete;
+    refcount_atom_impl& operator=(const refcount_atom_impl&) = delete;
+    refcount_atom_impl& operator=(refcount_atom_impl&&) = delete;
+
+    refcount_atom_impl(box_type b)
+        : impl_{std::move(b)}
+    {}
+
+    box_type load() const
+    {
+        scoped_lock_t lock{lock_};
+        return impl_;
+    }
+
+    void store(box_type b)
+    {
+        scoped_lock_t lock{lock_};
+        impl_ = std::move(b);
+    }
+
+    box_type exchange(box_type b)
+    {
+        {
+            scoped_lock_t lock{lock_};
+            swap(b, impl_);
+        }
+        return std::move(b);
+    }
+
+    template <typename Fn>
+    box_type update(Fn&& fn)
+    {
+        while (true) {
+            auto oldv = load();
+            auto newv = oldv.update(fn);
+            {
+                scoped_lock_t lock{lock_};
+                if (oldv.impl_ == impl_.impl_) {
+                    impl_ = newv;
+                    return { newv };
+                }
+            }
+        }
+    }
+
+private:
+    mutable spinlock_t lock_;
+    box_type impl_;
+};
+
+template <typename T, typename MemoryPolicy>
+struct gc_atom_impl
+{
+    using box_type = box<T, MemoryPolicy>;
+    using value_type = T;
+    using memory_policy = MemoryPolicy;
+
+    static_assert(
+        std::is_same<typename MemoryPolicy::refcount,
+                     no_refcount_policy>::value,
+        "gc_atom_impl can only be used when there is no refcount!");
+
+    gc_atom_impl(const gc_atom_impl&) = delete;
+    gc_atom_impl(gc_atom_impl&&) = delete;
+    gc_atom_impl& operator=(const gc_atom_impl&) = delete;
+    gc_atom_impl& operator=(gc_atom_impl&&) = delete;
+
+    gc_atom_impl(box_type b)
+        : impl_{b.impl_}
+    {}
+
+    box_type load() const
+    { return {impl_.load()}; }
+
+    void store(box_type b)
+    { impl_.store(b.impl_); }
+
+    box_type exchange(box_type b)
+    { return {impl_.exchange(b.impl_)}; }
+
+    template <typename Fn>
+    box_type update(Fn&& fn)
+    {
+        while (true) {
+            auto oldv = box_type{impl_.load()};
+            auto newv = oldv.update(fn);
+            if (impl_.compare_exchange_weak(oldv.impl_, newv.impl_))
+                return { newv };
+        }
+    }
+
+private:
+    std::atomic<typename box_type::holder*> impl_;
+};
+
+} // namespace detail
+
+/*!
+ * Stores for boxed values of type `T` in a thread-safe manner.
+ *
+ * @see box
+ *
+ * @rst
+ *
+ * .. warning:: If memory policy used includes thread unsafe reference counting,
+ *    no no thread safety is assumed, and the atom becomes thread unsafe too!
+ *
+ * .. note:: ``box<T>`` provides a value based box of type ``T``, this is, we can
+ *    think about it as a value-based version of ``std::shared_ptr``.  In a
+ *    similar fashion, ``atom<T>`` is in spirit the value-based equivalent of
+ *    C++20 ``std::atomic_shared_ptr``.  However, the API does not follow
+ *    ``std::atomic`` interface closely, since it attempts to be a higher level
+ *    construction, most similar to Clojure's ``(atom)``.  It is remarkable in
+ *    particular that, since ``box<T>`` underlying object is immutable, using
+ *    ``atom<T>`` is fully thread-safe in ways that ``std::atmic_shared_ptr`` is
+ *    not. This is so because dereferencing the underlying pointer in a
+ *    ``std::atomic_share_ptr`` may require further synchronization, in particular
+ *    when invoking non-const methods.
+ *
+ * @endrst
+ */
+template <typename T,
+          typename MemoryPolicy = default_memory_policy>
+class atom
+{
+public:
+    using box_type = box<T, MemoryPolicy>;
+    using value_type = T;
+    using memory_policy = MemoryPolicy;
+
+    atom(const atom&) = delete;
+    atom(atom&&) = delete;
+    void operator=(const atom&) = delete;
+    void operator=(atom&&) = delete;
+
+    /*!
+     * Constructs an atom holding a value `b`;
+     */
+    atom(box_type v={})
+        : impl_{std::move(v)}
+    {}
+
+    /*!
+     * Sets a new value in the atom.
+     */
+    atom& operator=(box_type b)
+    {
+        impl_.store(std::move(b));
+        return *this;
+    }
+
+    /*!
+     * Reads the currently stored value in a thread-safe manner.
+     */
+    operator box_type() const
+    { return impl_.load(); }
+
+    /*!
+     * Reads the currently stored value in a thread-safe manner.
+     */
+    operator value_type() const
+    { return *impl_.load(); }
+
+    /*!
+     * Reads the currently stored value in a thread-safe manner.
+     */
+    box_type load() const
+    { return impl_.load(); }
+
+    /*!
+     * Stores a new value in a thread-safe manner.
+     */
+    void store(box_type b)
+    { impl_.store(std::move(b)); }
+
+    /*!
+     * Stores a new value and returns the old value, in a thread-safe manner.
+     */
+    box_type exchange(box_type b)
+    { return impl_.exchange(std::move(b)); }
+
+    /*!
+     * Stores the result of applying `fn` to the current value atomically and
+     * returns the new resulting value.
+     *
+     * @rst
+     *
+     * .. warning:: ``fn`` must be a pure function and have no side effects! The
+     *    function might be evaluated multiple times when multiple threads
+     *    content to update the value.
+     *
+     * @endrst
+     */
+    template <typename Fn>
+    box_type update(Fn&& fn)
+    { return impl_.update(std::forward<Fn>(fn)); }
+
+private:
+    struct get_refcount_atom_impl
+    {
+        template <typename U, typename MP>
+        struct apply
+        {
+            using type = detail::refcount_atom_impl<U, MP>;
+        };
+    };
+
+    struct get_gc_atom_impl
+    {
+        template <typename U, typename MP>
+        struct apply
+        {
+            using type = detail::gc_atom_impl<U, MP>;
+        };
+    };
+
+    // If we are using "real" garbage collection (we assume this when we use
+    // `no_refcount_policy`), we just store the pointer in an atomic.  If we use
+    // reference counting, we rely on the reference counting spinlock.
+    using impl_t = typename std::conditional_t<
+        std::is_same<typename MemoryPolicy::refcount, no_refcount_policy>::value,
+        get_gc_atom_impl,
+        get_refcount_atom_impl
+    >::template apply<T, MemoryPolicy>::type;
+
+    impl_t impl_;
+};
+
+}

src/immer/box.hpp

@@ -13,6 +13,16 @@
 
 namespace immer {
 
+namespace detail {
+
+template <typename U, typename MP>
+struct gc_atom_impl;
+
+template <typename U, typename MP>
+struct refcount_atom_impl;
+
+} // namespace detail
+
 /*!
  * Immutable box for a single value of type `T`.
  *
@@ -21,9 +31,12 @@ namespace immer {
  * moving just copy the underlying pointers.
  */
 template <typename T,
-          typename MemoryPolicy   = default_memory_policy>
+          typename MemoryPolicy = default_memory_policy>
 class box
 {
+    friend struct detail::gc_atom_impl<T, MemoryPolicy>;
+    friend struct detail::refcount_atom_impl<T, MemoryPolicy>;
+
     struct holder : MemoryPolicy::refcount
     {
         T value;

src/immer/config.hpp

@@ -35,12 +35,20 @@
 #define IMMER_TRACE_E(expr)                             \
     IMMER_TRACE("    " << #expr << " = " << (expr))
 
+#if defined(_MSC_VER)
+#define IMMER_UNREACHABLE    __assume(false)
+#define IMMER_LIKELY(cond)   cond
+#define IMMER_UNLIKELY(cond) cond
+#define IMMER_FORCEINLINE    __forceinline
+#define IMMER_PREFETCH(p)
+#else
 #define IMMER_UNREACHABLE    __builtin_unreachable()
 #define IMMER_LIKELY(cond)   __builtin_expect(!!(cond), 1)
 #define IMMER_UNLIKELY(cond) __builtin_expect(!!(cond), 0)
-// #define IMMER_PREFETCH(p)    __builtin_prefetch(p)
-#define IMMER_PREFETCH(p)
 #define IMMER_FORCEINLINE    inline __attribute__ ((always_inline))
+#define IMMER_PREFETCH(p)
+// #define IMMER_PREFETCH(p)    __builtin_prefetch(p)
+#endif
 
 #define IMMER_DESCENT_DEEP 0
 

src/immer/detail/arrays/no_capacity.hpp

@@ -8,6 +8,7 @@
 
 #pragma once
 
+#include <immer/algorithm.hpp>
 #include <immer/detail/arrays/node.hpp>
 
 namespace immer {
@@ -90,10 +91,13 @@ struct no_capacity
     T* data() { return ptr->data(); }
     const T* data() const { return ptr->data(); }
 
-    template <typename Iter>
-    static no_capacity from_range(Iter first, Iter last)
+    template <typename Iter, typename Sent,
+              std::enable_if_t
+              <is_forward_iterator_v<Iter> 
+	       && compatible_sentinel_v<Iter, Sent>, bool> = true>
+    static no_capacity from_range(Iter first, Sent last)
     {
-        auto count = static_cast<size_t>(std::distance(first, last));
+        auto count = static_cast<size_t>(distance(first, last));
         return {
             node_t::copy_n(count, first, last),
             count,