From 23863230de1c57ef251becb399937f7a77ea83a9 Mon Sep 17 00:00:00 2001
From: Vinnie Falco <vinnie.falco@gmail.com>
Date: Fri, 9 Jun 2017 17:36:45 -0700
Subject: [PATCH] flat_buffer is an AllocatorAwareContainer

fix #453
---
 CHANGELOG.md                            |   2 +
 include/beast/core/flat_buffer.hpp      | 226 +++++++------
 include/beast/core/impl/flat_buffer.ipp | 412 +++++++++++++++++-------
 test/core/flat_buffer.cpp               |   6 +-
 4 files changed, 437 insertions(+), 209 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 59bbef07..2b297279 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,7 @@
 Version 52:
 
+* flat_buffer is an AllocatorAwareContainer
+
 API Changes:
 
 * `auto_fragment` is a member of `stream`
diff --git a/include/beast/core/flat_buffer.hpp b/include/beast/core/flat_buffer.hpp
index f67d0b51..9878a811 100644
--- a/include/beast/core/flat_buffer.hpp
+++ b/include/beast/core/flat_buffer.hpp
@@ -89,109 +89,120 @@ public:
     /// The type used to represent the output sequence as a list of buffers.
     using mutable_buffers_type = boost::asio::mutable_buffers_1;
 
-    /// Copy assignment (disallowed).
-    basic_flat_buffer&
-    operator=(basic_flat_buffer const&) = delete;
-
-    /// Destructor.
+    /// Destructor
     ~basic_flat_buffer();
 
-    /** Move constructor.
+    /** Constructor
 
-        The new object will have the same input sequence
-        and an empty output sequence.
-
-        @note After the move, the moved-from object will
-        have a capacity of zero, an empty input sequence,
-        and an empty output sequence.
+        Upon construction, capacity will be zero.
     */
-    basic_flat_buffer(basic_flat_buffer&&);
+    basic_flat_buffer();
 
-    /** Move constructor.
+    /** Constructor
 
-        The new object will have the same input sequence
-        and an empty output sequence.
+        Upon construction, capacity will be zero.
 
-        @note After the move, the moved-from object will
-        have a capacity of zero, an empty input sequence,
-        and an empty output sequence.
-
-        @param alloc The allocator to associate with the
-        stream buffer.
-    */
-    basic_flat_buffer(basic_flat_buffer&&,
-        Allocator const& alloc);
-    
-    /** Copy constructor.
-
-        The new object will have a copy of the input sequence
-        and an empty output sequence.
-    */
-    basic_flat_buffer(basic_flat_buffer const&);
-
-    /** Copy constructor.
-
-        The new object will have a copy of the input sequence
-        and an empty output sequence.
-
-        @param alloc The allocator to associate with the
-        stream buffer.
-    */
-    basic_flat_buffer(basic_flat_buffer const&,
-        Allocator const& alloc);
-    
-    /** Copy constructor.
-
-        The new object will have a copy of the input sequence
-        and an empty output sequence.
-    */
-    template<class OtherAlloc>
-    basic_flat_buffer(
-        basic_flat_buffer<OtherAlloc> const&);
-
-    /** Copy constructor.
-
-        The new object will have a copy of the input sequence
-        and an empty output sequence.
-
-        @param alloc The allocator to associate with the
-        stream buffer.
-    */
-    template<class OtherAlloc>
-    basic_flat_buffer(
-        basic_flat_buffer<OtherAlloc> const&,
-            Allocator const& alloc);
-
-    /** Construct a flat stream buffer.
-
-        No allocation is performed; the buffer will have
-        empty input and output sequences.
-
-        @param limit An optional non-zero value specifying the
-        maximum of the sum of the input and output sequence sizes
-        that can be allocated. If unspecified, the largest
-        possible value of `std::size_t` is used.
+        @param limit The setting for @ref max_size.
     */
     explicit
-    basic_flat_buffer(std::size_t limit = (
-        std::numeric_limits<std::size_t>::max)());
+    basic_flat_buffer(std::size_t limit);
 
-    /** Construct a flat stream buffer.
+    /** Constructor
 
-        No allocation is performed; the buffer will have
-        empty input and output sequences.
+        Upon construction, capacity will be zero.
 
-        @param alloc The allocator to associate with the
-        stream buffer.
-
-        @param limit An optional non-zero value specifying the
-        maximum of the sum of the input and output sequence sizes
-        that can be allocated. If unspecified, the largest
-        possible value of `std::size_t` is used.
+        @param alloc The allocator to construct with.
     */
-    basic_flat_buffer(Allocator const& alloc,
-        std::size_t limit = (
-            std::numeric_limits<std::size_t>::max)());
+    explicit
+    basic_flat_buffer(Allocator const& alloc);
+
+    /** Constructor
+
+        Upon construction, capacity will be zero.
+
+        @param limit The setting for @ref max_size.
+
+        @param alloc The allocator to use.
+    */
+    basic_flat_buffer(
+        std::size_t limit, Allocator const& alloc);
+
+    /** Move constructor
+
+        After the move, `*this` will have an empty output sequence.
+
+        @param other The object to move from. After the move,
+        The object's state will be as if constructed using
+        its current allocator and limit.
+    */
+    basic_flat_buffer(basic_flat_buffer&& other);
+
+    /** Move constructor
+
+        After the move, `*this` will have an empty output sequence.
+
+        @param other The object to move from. After the move,
+        The object's state will be as if constructed using
+        its current allocator and limit.
+
+        @param alloc The allocator to use.
+    */
+    basic_flat_buffer(
+        basic_flat_buffer&& other, Allocator const& alloc);
+
+    /** Copy constructor
+
+        @param other The object to copy from.
+    */
+    basic_flat_buffer(basic_flat_buffer const& other);
+
+    /** Copy constructor
+
+        @param other The object to copy from.
+
+        @param alloc The allocator to use.
+    */
+    basic_flat_buffer(basic_flat_buffer const& other,
+        Allocator const& alloc);
+
+    /** Copy constructor
+
+        @param other The object to copy from.
+    */
+    template<class OtherAlloc>
+    basic_flat_buffer(
+        basic_flat_buffer<OtherAlloc> const& other);
+
+    /** Copy constructor
+
+        @param other The object to copy from.
+
+        @param alloc The allocator to use.
+    */
+    template<class OtherAlloc>
+    basic_flat_buffer(
+        basic_flat_buffer<OtherAlloc> const& other,
+            Allocator const& alloc);
+
+    /** Move assignment
+
+        After the move, `*this` will have an empty output sequence.
+
+        @param other The object to move from. After the move,
+        The object's state will be as if constructed using
+        its current allocator and limit.
+    */
+    basic_flat_buffer&
+    operator=(basic_flat_buffer&& other);
+
+    /** Copy assignment
+
+        After the copy, `*this` will have an empty output sequence.
+
+        @param other The object to copy from.
+    */
+    basic_flat_buffer&
+    operator=(basic_flat_buffer const& other);
 
     /// Returns a copy of the associated allocator.
     allocator_type
@@ -287,14 +298,41 @@ public:
     void
     shrink_to_fit();
 
+    template<class Alloc>
+    friend
+    void
+    swap(
+        basic_flat_buffer<Alloc>& lhs,
+        basic_flat_buffer<Alloc>& rhs);
+
 private:
     void
-    move_from(basic_flat_buffer& other);
+    reset();
 
-    template<class OtherAlloc>
+    template<class DynamicBuffer>
     void
-    copy_from(basic_flat_buffer<
-        OtherAlloc> const& other);
+    copy_from(DynamicBuffer const& other);
+
+    void
+    move_assign(basic_flat_buffer&, std::true_type);
+
+    void
+    move_assign(basic_flat_buffer&, std::false_type);
+
+    void
+    copy_assign(basic_flat_buffer const&, std::true_type);
+
+    void
+    copy_assign(basic_flat_buffer const&, std::false_type);
+
+    void
+    swap(basic_flat_buffer&);
+
+    void
+    swap(basic_flat_buffer&, std::true_type);
+
+    void
+    swap(basic_flat_buffer&, std::false_type);
 };
 
 using flat_buffer =
diff --git a/include/beast/core/impl/flat_buffer.ipp b/include/beast/core/impl/flat_buffer.ipp
index 99668754..66a01099 100644
--- a/include/beast/core/impl/flat_buffer.ipp
+++ b/include/beast/core/impl/flat_buffer.ipp
@@ -36,50 +36,7 @@ next_pow2(std::size_t x)
 
 } // detail
 
-template<class Allocator>
-void
-basic_flat_buffer<Allocator>::
-move_from(basic_flat_buffer& other)
-{
-    begin_ = other.begin_;
-    in_ = other.in_;
-    out_ = other.out_;
-    last_ = out_;
-    end_ = other.end_;
-    max_ = other.max_;
-    other.begin_ = nullptr;
-    other.in_ = nullptr;
-    other.out_ = nullptr;
-    other.last_ = nullptr;
-    other.end_ = nullptr;
-}
-
-template<class Allocator>
-template<class OtherAlloc>
-void
-basic_flat_buffer<Allocator>::
-copy_from(basic_flat_buffer<
-    OtherAlloc> const& other)
-{
-    max_ = other.max_;
-    auto const n = other.size();
-    if(n > 0)
-    {
-        begin_ = alloc_traits::allocate(
-            this->member(), n);
-        in_ = begin_;
-        out_ = begin_ + n;
-        last_ = out_;
-        end_ = out_;
-        std::memcpy(in_, other.in_, n);
-        return;
-    }
-    begin_ = nullptr;
-    in_ = nullptr;
-    out_ = nullptr;
-    last_ = nullptr;
-    end_ = nullptr;
-}
+//------------------------------------------------------------------------------
 
 template<class Allocator>
 basic_flat_buffer<Allocator>::
@@ -92,69 +49,14 @@ basic_flat_buffer<Allocator>::
 
 template<class Allocator>
 basic_flat_buffer<Allocator>::
-basic_flat_buffer(basic_flat_buffer&& other)
-    : detail::empty_base_optimization<
-        allocator_type>(std::move(other.member()))
+basic_flat_buffer()
+    : begin_(nullptr)
+    , in_(nullptr)
+    , out_(nullptr)
+    , last_(nullptr)
+    , end_(nullptr)
+    , max_((std::numeric_limits<std::size_t>::max)())
 {
-    move_from(other);
-}
-
-template<class Allocator>
-basic_flat_buffer<Allocator>::
-basic_flat_buffer(basic_flat_buffer&& other,
-        Allocator const& alloc)
-    : detail::empty_base_optimization<
-        allocator_type>(alloc)
-{
-    if(this->member() != other.member())
-    {
-        copy_from(other);
-        return;
-    }
-    move_from(other);
-}
-
-template<class Allocator>
-basic_flat_buffer<Allocator>::
-basic_flat_buffer(
-        basic_flat_buffer const& other)
-    : detail::empty_base_optimization<allocator_type>(
-        alloc_traits::select_on_container_copy_construction(
-            other.member()))
-{
-    copy_from(other);
-}
-
-template<class Allocator>
-basic_flat_buffer<Allocator>::
-basic_flat_buffer(
-    basic_flat_buffer const& other,
-        Allocator const& alloc)
-    : detail::empty_base_optimization<
-        allocator_type>(alloc)
-{
-    copy_from(other);
-}
-    
-template<class Allocator>
-template<class OtherAlloc>
-basic_flat_buffer<Allocator>::
-basic_flat_buffer(
-    basic_flat_buffer<OtherAlloc> const& other)
-{
-    copy_from(other);
-}
-
-template<class Allocator>
-template<class OtherAlloc>
-basic_flat_buffer<Allocator>::
-basic_flat_buffer(
-    basic_flat_buffer<OtherAlloc> const& other,
-        Allocator const& alloc)
-    : detail::empty_base_optimization<
-        allocator_type>(alloc)
-{
-    copy_from(other);
 }
 
 template<class Allocator>
@@ -167,15 +69,25 @@ basic_flat_buffer(std::size_t limit)
     , end_(nullptr)
     , max_(limit)
 {
-    BOOST_ASSERT(limit >= 1);
 }
 
 template<class Allocator>
 basic_flat_buffer<Allocator>::
-basic_flat_buffer(Allocator const& alloc,
-        std::size_t limit)
-    : detail::empty_base_optimization<
-        allocator_type>(alloc)
+basic_flat_buffer(Allocator const& alloc)
+    : detail::empty_base_optimization<allocator_type>(alloc)
+    , begin_(nullptr)
+    , in_(nullptr)
+    , out_(nullptr)
+    , last_(nullptr)
+    , end_(nullptr)
+    , max_((std::numeric_limits<std::size_t>::max)())
+{
+}
+
+template<class Allocator>
+basic_flat_buffer<Allocator>::
+basic_flat_buffer(std::size_t limit, Allocator const& alloc)
+    : detail::empty_base_optimization<allocator_type>(alloc)
     , begin_(nullptr)
     , in_(nullptr)
     , out_(nullptr)
@@ -183,9 +95,148 @@ basic_flat_buffer(Allocator const& alloc,
     , end_(nullptr)
     , max_(limit)
 {
-    BOOST_ASSERT(limit >= 1);
 }
 
+template<class Allocator>
+basic_flat_buffer<Allocator>::
+basic_flat_buffer(basic_flat_buffer&& other)
+    : detail::empty_base_optimization<allocator_type>(
+        std::move(other.member()))
+    , begin_(other.begin_)
+    , in_(other.in_)
+    , out_(other.out_)
+    , last_(out_)
+    , end_(other.end_)
+    , max_(other.max_)
+{
+    other.begin_ = nullptr;
+    other.in_ = nullptr;
+    other.out_ = nullptr;
+    other.last_ = nullptr;
+    other.end_ = nullptr;
+}
+
+template<class Allocator>
+basic_flat_buffer<Allocator>::
+basic_flat_buffer(basic_flat_buffer&& other,
+        Allocator const& alloc)
+    : detail::empty_base_optimization<allocator_type>(alloc)
+{
+    if(this->member() != other.member())
+    {
+        begin_ = nullptr;
+        in_ = nullptr;
+        out_ = nullptr;
+        last_ = nullptr;
+        end_ = nullptr;
+        max_ = other.max_;
+        copy_from(other);
+        other.reset();
+    }
+    else
+    {
+        begin_ = other.begin_;
+        in_ = other.in_;
+        out_ = other.out_;
+        last_ = out_;
+        end_ = other.end_;
+        max_ = other.max_;
+        other.begin_ = nullptr;
+        other.in_ = nullptr;
+        other.out_ = nullptr;
+        other.last_ = nullptr;
+        other.end_ = nullptr;
+    }
+}
+
+template<class Allocator>
+basic_flat_buffer<Allocator>::
+basic_flat_buffer(basic_flat_buffer const& other)
+    : detail::empty_base_optimization<allocator_type>(
+        alloc_traits::select_on_container_copy_construction(
+            other.member()))
+    , begin_(nullptr)
+    , in_(nullptr)
+    , out_(nullptr)
+    , last_(nullptr)
+    , end_(nullptr)
+    , max_(other.max_)
+{
+    copy_from(other);
+}
+
+template<class Allocator>
+basic_flat_buffer<Allocator>::
+basic_flat_buffer(basic_flat_buffer const& other,
+        Allocator const& alloc)
+    : detail::empty_base_optimization<allocator_type>(alloc)
+    , begin_(nullptr)
+    , in_(nullptr)
+    , out_(nullptr)
+    , last_(nullptr)
+    , end_(nullptr)
+    , max_(other.max_)
+{
+    copy_from(other);
+}
+
+template<class Allocator>
+template<class OtherAlloc>
+basic_flat_buffer<Allocator>::
+basic_flat_buffer(
+        basic_flat_buffer<OtherAlloc> const& other)
+    : begin_(nullptr)
+    , in_(nullptr)
+    , out_(nullptr)
+    , last_(nullptr)
+    , end_(nullptr)
+    , max_(other.max_)
+{
+    copy_from(other);
+}
+
+template<class Allocator>
+template<class OtherAlloc>
+basic_flat_buffer<Allocator>::
+basic_flat_buffer(basic_flat_buffer<OtherAlloc> const& other,
+        Allocator const& alloc)
+    : detail::empty_base_optimization<allocator_type>(alloc)
+    , begin_(nullptr)
+    , in_(nullptr)
+    , out_(nullptr)
+    , last_(nullptr)
+    , end_(nullptr)
+    , max_(other.max_)
+{
+    copy_from(other);
+}
+
+template<class Allocator>
+auto
+basic_flat_buffer<Allocator>::
+operator=(basic_flat_buffer&& other) ->
+    basic_flat_buffer&
+{
+    if(this != &other)
+        move_assign(other,
+            typename alloc_traits::propagate_on_container_move_assignment{});
+    return *this;
+}
+
+template<class Allocator>
+auto
+basic_flat_buffer<Allocator>::
+operator=(basic_flat_buffer const& other) ->
+    basic_flat_buffer&
+{
+    if(this != &other)
+        copy_assign(other,
+            typename alloc_traits::propagate_on_container_copy_assignment{});
+    return *this;
+}
+
+//------------------------------------------------------------------------------
+
 template<class Allocator>
 auto
 basic_flat_buffer<Allocator>::
@@ -311,6 +362,143 @@ shrink_to_fit()
     end_ = out_;
 }
 
+//------------------------------------------------------------------------------
+
+template<class Allocator>
+inline
+void
+basic_flat_buffer<Allocator>::
+reset()
+{
+    consume(size());
+    shrink_to_fit();
+}
+
+template<class Allocator>
+template<class DynamicBuffer>
+inline
+void
+basic_flat_buffer<Allocator>::
+copy_from(DynamicBuffer const& buffer)
+{
+    if(buffer.size() == 0)
+        return;
+    using boost::asio::buffer_copy;
+    commit(buffer_copy(
+        prepare(buffer.size()), buffer.data()));
+}
+
+template<class Allocator>
+inline
+void
+basic_flat_buffer<Allocator>::
+move_assign(basic_flat_buffer& other, std::true_type)
+{
+    reset();
+    this->member() = std::move(other.member());
+    begin_ = other.begin_;
+    in_ = other.in_;
+    out_ = other.out_;
+    last_ = out_;
+    end_ = other.end_;
+    max_ = other.max_;
+    other.begin_ = nullptr;
+    other.in_ = nullptr;
+    other.out_ = nullptr;
+    other.last_ = nullptr;
+    other.end_ = nullptr;
+}
+
+template<class Allocator>
+inline
+void
+basic_flat_buffer<Allocator>::
+move_assign(basic_flat_buffer& other, std::false_type)
+{
+    reset();
+    if(this->member() != other.member())
+    {
+        copy_from(other);
+        other.reset();
+    }
+    else
+    {
+        move_assign(other, std::true_type{});
+    }
+}
+
+template<class Allocator>
+inline
+void
+basic_flat_buffer<Allocator>::
+copy_assign(basic_flat_buffer const& other, std::true_type)
+{
+    reset();
+    this->member() = other.member();
+    copy_from(other);
+}
+
+template<class Allocator>
+inline
+void
+basic_flat_buffer<Allocator>::
+copy_assign(basic_flat_buffer const& other, std::false_type)
+{
+    reset();
+    copy_from(other);
+}
+
+template<class Allocator>
+inline
+void
+basic_flat_buffer<Allocator>::
+swap(basic_flat_buffer& other)
+{
+    swap(other,
+        typename alloc_traits::propagate_on_container_swap{});
+}
+
+template<class Allocator>
+inline
+void
+basic_flat_buffer<Allocator>::
+swap(basic_flat_buffer& other, std::true_type)
+{
+    using std::swap;
+    swap(this->member(), other.member());
+    swap(this->begin_, other.begin_);
+    swap(this->in_, other.in_);
+    swap(this->out_, other.out_);
+    this->last_ = this->out_;
+    other->last_ = other->out_;
+    swap(this->end_, other.end_);
+}
+
+template<class Allocator>
+inline
+void
+basic_flat_buffer<Allocator>::
+swap(basic_flat_buffer& other, std::false_type)
+{
+    BOOST_ASSERT(this->member() == other.member());
+    using std::swap;
+    swap(this->begin_, other.begin_);
+    swap(this->in_, other.in_);
+    swap(this->out_, other.out_);
+    this->last_ = this->out_;
+    other->last_ = other->out_;
+    swap(this->end_, other.end_);
+}
+
+template<class Allocator>
+void
+swap(
+    basic_flat_buffer<Allocator>& lhs,
+    basic_flat_buffer<Allocator>& rhs)
+{
+    lhs.swap(rhs);
+}
+
 } // beast
 
 #endif
diff --git a/test/core/flat_buffer.cpp b/test/core/flat_buffer.cpp
index 45da3b3c..b336033a 100644
--- a/test/core/flat_buffer.cpp
+++ b/test/core/flat_buffer.cpp
@@ -87,7 +87,7 @@ public:
             basic_flat_buffer<allocator> b1{10};
         }
         {
-            basic_flat_buffer<allocator> b1{allocator{}, 10};
+            basic_flat_buffer<allocator> b1{10, allocator{}};
         }
     }
 
@@ -193,11 +193,11 @@ public:
                 basic_flat_buffer<alloc_type>;
             alloc_type alloc;
             {
-                type fba{alloc, 1};
+                type fba{1, alloc};
                 BEAST_EXPECT(fba.max_size() == 1);
             }
             {
-                type fba{alloc, 1024};
+                type fba{1024, alloc};
                 BEAST_EXPECT(fba.max_size() == 1024);
             }
             {