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 //
 // Copyright (c) 2020 Vinnie Falco (vinnie.falco@gmail.com)
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 //
 // Official repository: https://github.com/boostorg/json
 //
 
 #ifndef BOOST_JSON_STATIC_RESOURCE_HPP
 #define BOOST_JSON_STATIC_RESOURCE_HPP
 
 #include <boost/container/pmr/memory_resource.hpp>
 #include <boost/json/detail/config.hpp>
 #include <boost/json/is_deallocate_trivial.hpp>
 #include <cstddef>
 
 namespace boost {
 namespace json {
 
 #ifdef _MSC_VER
 #pragma warning(push)
 #pragma warning(disable: 4275) // non dll-interface class used as base for dll-interface class
 #endif
 
 //----------------------------------------------------------
 
 /** A resource using a caller-owned buffer, with a trivial deallocate
 
     This memory resource is a special-purpose resource
     that releases allocated memory only when the resource
     is destroyed (or when @ref release is called).
     It has a trivial deallocate function; that is, the
     metafunction @ref is_deallocate_trivial returns `true`.
 \n
     The resource is constructed from a caller-owned buffer
     from which subsequent calls to allocate are apportioned.
     When a memory request cannot be satisfied from the
     free bytes remaining in the buffer, the allocation
     request fails with the exception `std::bad_alloc`.
 \n
     @par Example
 
     This parses a JSON text into a value which uses a local
     stack buffer, then prints the result.
 
     @code
 
     unsigned char buf[ 4000 ];
     static_resource mr( buf );
 
     // Parse the string, using our memory resource
     value const jv = parse( "[1,2,3]", &mr );
 
     // Print the JSON
     std::cout << jv;
 
     @endcode
 
     @par Thread Safety
     Members of the same instance may not be
     called concurrently.
 
     @see
         https://en.wikipedia.org/wiki/Region-based_memory_management
 */
 class
     BOOST_JSON_DECL
     BOOST_SYMBOL_VISIBLE
 static_resource final
     : public container::pmr::memory_resource
 {
     void* p_;
     std::size_t n_;
     std::size_t size_;
 
 public:
     /// Copy constructor (deleted)
     static_resource(
         static_resource const&) = delete;
 
     /// Copy assignment (deleted)
     static_resource& operator=(
         static_resource const&) = delete;
 
     /** Constructor
 
         This constructs the resource to use the specified
         buffer for subsequent calls to allocate. When the
         buffer is exhausted, allocate will throw
         `std::bad_alloc`.
 
         @par Complexity
         Constant.
 
         @par Exception Safety
         No-throw guarantee.
 
         @param buffer The buffer to use.
         Ownership is not transferred; the caller is
         responsible for ensuring that the lifetime of
         the buffer extends until the resource is destroyed.
 
         @param size The number of valid bytes pointed
         to by `buffer`.
     */
     /** @{ */
     static_resource(
         unsigned char* buffer,
         std::size_t size) noexcept;
 
 #if defined(__cpp_lib_byte) || defined(BOOST_JSON_DOCS)
     static_resource(
         std::byte* buffer,
         std::size_t size) noexcept
         : static_resource(reinterpret_cast<
             unsigned char*>(buffer), size)
     {
     }
 #endif
     /** @} */
 
     /** Constructor
 
         This constructs the resource to use the specified
         buffer for subsequent calls to allocate. When the
         buffer is exhausted, allocate will throw
         `std::bad_alloc`.
 
         @par Complexity
         Constant.
 
         @par Exception Safety
         No-throw guarantee.
 
         @param buffer The buffer to use.
         Ownership is not transferred; the caller is
         responsible for ensuring that the lifetime of
         the buffer extends until the resource is destroyed.
     */
     /** @{ */
     template<std::size_t N>
     explicit
     static_resource(
         unsigned char(&buffer)[N]) noexcept
         : static_resource(&buffer[0], N)
     {
     }
 
 #if defined(__cpp_lib_byte) || defined(BOOST_JSON_DOCS)
     template<std::size_t N>
     explicit
     static_resource(
         std::byte(&buffer)[N]) noexcept
         : static_resource(&buffer[0], N)
     {
     }
 #endif
     /** @} */
 
 #ifndef BOOST_JSON_DOCS
     // Safety net for accidental buffer overflows
     template<std::size_t N>
     static_resource(
         unsigned char(&buffer)[N], std::size_t n) noexcept
         : static_resource(&buffer[0], n)
     {
         // If this goes off, check your parameters
         // closely, chances are you passed an array
         // thinking it was a pointer.
         BOOST_ASSERT(n <= N);
     }
 
 #ifdef __cpp_lib_byte
     // Safety net for accidental buffer overflows
     template<std::size_t N>
     static_resource(
         std::byte(&buffer)[N], std::size_t n) noexcept
         : static_resource(&buffer[0], n)
     {
         // If this goes off, check your parameters
         // closely, chances are you passed an array
         // thinking it was a pointer.
         BOOST_ASSERT(n <= N);
     }
 #endif
 #endif
 
     /** Release all allocated memory.
 
         This function resets the buffer provided upon
         construction so that all of the valid bytes are
         available for subsequent allocation.
 
         @par Complexity
         Constant
 
         @par Exception Safety
         No-throw guarantee.
     */
     void
     release() noexcept;
 
 protected:
 #ifndef BOOST_JSON_DOCS
     void*
     do_allocate(
         std::size_t n,
         std::size_t align) override;
 
     void
     do_deallocate(
         void* p,
         std::size_t n,
         std::size_t align) override;
 
     bool
     do_is_equal(
         memory_resource const& mr
             ) const noexcept override;
 #endif
 };
 
 #ifdef _MSC_VER
 #pragma warning(pop)
 #endif
 
 template<>
 struct is_deallocate_trivial<
     static_resource>
 {
     static constexpr bool value = true;
 };
 
 } // namespace json
 } // namespace boost
 
 #endif

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