From 1d055261b4144dbf86b2658437015b15d4dd9bff Mon Sep 17 00:00:00 2001
From: Richard <q@1bpm.net>
Date: Sun, 4 Sep 2022 00:32:56 +0100
Subject: initial

---
 include/jsoncons/decode_traits.hpp | 651 +++++++++++++++++++++++++++++++++++++
 1 file changed, 651 insertions(+)
 create mode 100644 include/jsoncons/decode_traits.hpp

(limited to 'include/jsoncons/decode_traits.hpp')

diff --git a/include/jsoncons/decode_traits.hpp b/include/jsoncons/decode_traits.hpp
new file mode 100644
index 0000000..2c9ee6e
--- /dev/null
+++ b/include/jsoncons/decode_traits.hpp
@@ -0,0 +1,651 @@
+// Copyright 2017 Daniel Parker
+// Distributed under the Boost license, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+// See https://github.com/danielaparker/jsoncons for latest version
+
+#ifndef JSONCONS_DECODE_TRAITS_HPP
+#define JSONCONS_DECODE_TRAITS_HPP
+
+#include <string>
+#include <tuple>
+#include <array>
+#include <memory>
+#include <type_traits> // std::enable_if, std::true_type, std::false_type
+#include <jsoncons/json_visitor.hpp>
+#include <jsoncons/json_decoder.hpp>
+#include <jsoncons/json_type_traits.hpp>
+#include <jsoncons/staj_cursor.hpp>
+#include <jsoncons/conv_error.hpp>
+#include <jsoncons/more_type_traits.hpp>
+
+namespace jsoncons {
+
+    // decode_traits
+
+    template <class T, class CharT, class Enable = void>
+    struct decode_traits
+    {
+        template <class Json,class TempAllocator>
+        static T decode(basic_staj_cursor<CharT>& cursor, 
+                        json_decoder<Json,TempAllocator>& decoder, 
+                        std::error_code& ec)
+        {
+            decoder.reset();
+            cursor.read_to(decoder, ec);
+            if (ec)
+            {
+                JSONCONS_THROW(ser_error(ec, cursor.context().line(), cursor.context().column()));
+            }
+            else if (!decoder.is_valid())
+            {
+                JSONCONS_THROW(ser_error(conv_errc::conversion_failed, cursor.context().line(), cursor.context().column()));
+            }
+            return decoder.get_result().template as<T>();
+        }
+    };
+
+    // specializations
+
+    // primitive
+
+    template <class T, class CharT>
+    struct decode_traits<T,CharT,
+        typename std::enable_if<type_traits::is_primitive<T>::value
+    >::type>
+    {
+        template <class Json,class TempAllocator>
+        static T decode(basic_staj_cursor<CharT>& cursor, 
+                        json_decoder<Json,TempAllocator>&, 
+                        std::error_code& ec)
+        {
+            T v = cursor.current().template get<T>(ec);
+            return v;
+        }
+    };
+
+    // string
+
+    template <class T, class CharT>
+    struct decode_traits<T,CharT,
+        typename std::enable_if<type_traits::is_basic_string<T>::value &&
+                                std::is_same<typename T::value_type,CharT>::value
+    >::type>
+    {
+        template <class Json,class TempAllocator>
+        static T decode(basic_staj_cursor<CharT>& cursor, 
+                        json_decoder<Json,TempAllocator>&, 
+                        std::error_code& ec)
+        {
+            T v = cursor.current().template get<T>(ec);
+            return v;
+        }
+    };
+
+    template <class T, class CharT>
+    struct decode_traits<T,CharT,
+        typename std::enable_if<type_traits::is_basic_string<T>::value &&
+                                !std::is_same<typename T::value_type,CharT>::value
+    >::type>
+    {
+        template <class Json,class TempAllocator>
+        static T decode(basic_staj_cursor<CharT>& cursor, 
+                        json_decoder<Json,TempAllocator>&, 
+                        std::error_code& ec)
+        {
+            auto val = cursor.current().template get<std::basic_string<CharT>>(ec);
+            T s;
+            if (!ec)
+            {
+                unicode_traits::convert(val.data(), val.size(), s);
+            }
+            return s;
+        }
+    };
+
+    // std::pair
+
+    template <class T1, class T2, class CharT>
+    struct decode_traits<std::pair<T1, T2>, CharT>
+    {
+        template <class Json, class TempAllocator>
+        static std::pair<T1, T2> decode(basic_staj_cursor<CharT>& cursor,
+                                        json_decoder<Json, TempAllocator>& decoder,
+                                        std::error_code& ec)
+        {
+            using value_type = std::pair<T1, T2>;
+            cursor.array_expected(ec);
+            if (ec)
+            {
+                return value_type{};
+            }
+            if (cursor.current().event_type() != staj_event_type::begin_array)
+            {
+                ec = conv_errc::not_pair;
+                return value_type();
+            }
+            cursor.next(ec); // skip past array
+            if (ec)
+            {
+                return value_type();
+            }
+
+            T1 v1 = decode_traits<T1,CharT>::decode(cursor, decoder, ec);
+            if (ec) {return value_type();}
+            cursor.next(ec);
+            if (ec) {return value_type();}
+            T2 v2 = decode_traits<T2, CharT>::decode(cursor, decoder, ec);
+            if (ec) {return value_type();}
+            cursor.next(ec);
+
+            if (cursor.current().event_type() != staj_event_type::end_array)
+            {
+                ec = conv_errc::not_pair;
+                return value_type();
+            }
+            return std::make_pair(v1, v2);
+        }
+    };
+
+    // vector like
+    template <class T, class CharT>
+    struct decode_traits<T,CharT,
+        typename std::enable_if<!is_json_type_traits_declared<T>::value && 
+                 type_traits::is_list_like<T>::value &&
+                 type_traits::is_back_insertable<T>::value &&
+                 !type_traits::is_typed_array<T>::value 
+    >::type>
+    {
+        using value_type = typename T::value_type;
+
+        template <class Json,class TempAllocator>
+        static T decode(basic_staj_cursor<CharT>& cursor, 
+                        json_decoder<Json,TempAllocator>& decoder, 
+                        std::error_code& ec)
+        {
+            T v;
+
+            cursor.array_expected(ec);
+            if (ec)
+            {
+                return T{};
+            }
+            if (cursor.current().event_type() != staj_event_type::begin_array)
+            {
+                ec = conv_errc::not_vector;
+                return v;
+            }
+            cursor.next(ec);
+            while (cursor.current().event_type() != staj_event_type::end_array && !ec)
+            {
+                v.push_back(decode_traits<value_type,CharT>::decode(cursor, decoder, ec));
+                if (ec) {return T{};}
+                cursor.next(ec);
+            }
+            return v;
+        }
+    };
+
+    template <class T>
+    struct typed_array_visitor : public default_json_visitor
+    {
+        T& v_;
+        int level_;
+    public:
+        using value_type = typename T::value_type;
+
+        typed_array_visitor(T& v)
+            : default_json_visitor(false,conv_errc::not_vector), v_(v), level_(0)
+        {
+        }
+    private:
+        bool visit_begin_array(semantic_tag, 
+                               const ser_context&, 
+                               std::error_code& ec) override
+        {      
+            if (++level_ != 1)
+            {
+                ec = conv_errc::not_vector;
+                return false;
+            }
+            return true;
+        }
+
+        bool visit_begin_array(std::size_t size, 
+                            semantic_tag, 
+                            const ser_context&, 
+                            std::error_code& ec) override
+        {
+            if (++level_ != 1)
+            {
+                ec = conv_errc::not_vector;
+                return false;
+            }
+            if (size > 0)
+            {
+                reserve_storage(typename std::integral_constant<bool, type_traits::has_reserve<T>::value>::type(), v_, size);
+            }
+            return true;
+        }
+
+        bool visit_end_array(const ser_context&, 
+                          std::error_code& ec) override
+        {
+            if (level_ != 1)
+            {
+                ec = conv_errc::not_vector;
+                return false;
+            }
+            return false;
+        }
+
+        bool visit_uint64(uint64_t value, 
+                             semantic_tag, 
+                             const ser_context&,
+                             std::error_code&) override
+        {
+            v_.push_back(static_cast<value_type>(value));
+            return true;
+        }
+
+        bool visit_int64(int64_t value, 
+                            semantic_tag,
+                            const ser_context&,
+                            std::error_code&) override
+        {
+            v_.push_back(static_cast<value_type>(value));
+            return true;
+        }
+
+        bool visit_half(uint16_t value, 
+                           semantic_tag,
+                           const ser_context&,
+                           std::error_code&) override
+        {
+            return visit_half_(typename std::integral_constant<bool, std::is_integral<value_type>::value>::type(), value);
+        }
+
+        bool visit_half_(std::true_type, uint16_t value)
+        {
+            v_.push_back(static_cast<value_type>(value));
+            return true;
+        }
+
+        bool visit_half_(std::false_type, uint16_t value)
+        {
+            v_.push_back(static_cast<value_type>(binary::decode_half(value)));
+            return true;
+        }
+
+        bool visit_double(double value, 
+                             semantic_tag,
+                             const ser_context&,
+                             std::error_code&) override
+        {
+            v_.push_back(static_cast<value_type>(value));
+            return true;
+        }
+
+        bool visit_typed_array(const jsoncons::span<const value_type>& data,  
+                            semantic_tag,
+                            const ser_context&,
+                            std::error_code&) override
+        {
+            v_ = std::vector<value_type>(data.begin(),data.end());
+            return false;
+        }
+
+        static
+        void reserve_storage(std::true_type, T& v, std::size_t new_cap)
+        {
+            v.reserve(new_cap);
+        }
+
+        static
+        void reserve_storage(std::false_type, T&, std::size_t)
+        {
+        }
+    };
+
+    template <class T, class CharT>
+    struct decode_traits<T,CharT,
+        typename std::enable_if<!is_json_type_traits_declared<T>::value && 
+                 type_traits::is_list_like<T>::value &&
+                 type_traits::is_back_insertable_byte_container<T>::value &&
+                 type_traits::is_typed_array<T>::value
+    >::type>
+    {
+        using value_type = typename T::value_type;
+
+        template <class Json,class TempAllocator>
+        static T decode(basic_staj_cursor<CharT>& cursor, 
+                        json_decoder<Json,TempAllocator>&, 
+                        std::error_code& ec)
+        {
+            cursor.array_expected(ec);
+            if (ec)
+            {
+                return T{};
+            }
+            switch (cursor.current().event_type())
+            {
+                case staj_event_type::byte_string_value:
+                {
+                    auto bytes = cursor.current().template get<byte_string_view>(ec);
+                    if (!ec) 
+                    {
+                        T v;
+                        if (cursor.current().size() > 0)
+                        {
+                            reserve_storage(typename std::integral_constant<bool, type_traits::has_reserve<T>::value>::type(), v, cursor.current().size());
+                        }
+                        for (auto ch : bytes)
+                        {
+                            v.push_back(static_cast<value_type>(ch));
+                        }
+                        cursor.next(ec);
+                        return v;
+                    }
+                    else
+                    {
+                        return T{};
+                    }
+                }
+                case staj_event_type::begin_array:
+                {
+                    T v;
+                    if (cursor.current().size() > 0)
+                    {
+                        reserve_storage(typename std::integral_constant<bool, type_traits::has_reserve<T>::value>::type(), v, cursor.current().size());
+                    }
+                    typed_array_visitor<T> visitor(v);
+                    cursor.read_to(visitor, ec);
+                    return v;
+                }
+                default:
+                {
+                    ec = conv_errc::not_vector;
+                    return T{};
+                }
+            }
+        }
+
+        static void reserve_storage(std::true_type, T& v, std::size_t new_cap)
+        {
+            v.reserve(new_cap);
+        }
+
+        static void reserve_storage(std::false_type, T&, std::size_t)
+        {
+        }
+    };
+
+    template <class T, class CharT>
+    struct decode_traits<T,CharT,
+        typename std::enable_if<!is_json_type_traits_declared<T>::value && 
+                 type_traits::is_list_like<T>::value &&
+                 type_traits::is_back_insertable<T>::value &&
+                 !type_traits::is_back_insertable_byte_container<T>::value &&
+                 type_traits::is_typed_array<T>::value
+    >::type>
+    {
+        using value_type = typename T::value_type;
+
+        template <class Json,class TempAllocator>
+        static T decode(basic_staj_cursor<CharT>& cursor, 
+                        json_decoder<Json,TempAllocator>&, 
+                        std::error_code& ec)
+        {
+            cursor.array_expected(ec);
+            if (ec)
+            {
+                return T{};
+            }
+            switch (cursor.current().event_type())
+            {
+                case staj_event_type::begin_array:
+                {
+                    T v;
+                    if (cursor.current().size() > 0)
+                    {
+                        reserve_storage(typename std::integral_constant<bool, type_traits::has_reserve<T>::value>::type(), v, cursor.current().size());
+                    }
+                    typed_array_visitor<T> visitor(v);
+                    cursor.read_to(visitor, ec);
+                    return v;
+                }
+                default:
+                {
+                    ec = conv_errc::not_vector;
+                    return T{};
+                }
+            }
+        }
+
+        static void reserve_storage(std::true_type, T& v, std::size_t new_cap)
+        {
+            v.reserve(new_cap);
+        }
+
+        static void reserve_storage(std::false_type, T&, std::size_t)
+        {
+        }
+    };
+
+    // set like
+    template <class T, class CharT>
+    struct decode_traits<T,CharT,
+        typename std::enable_if<!is_json_type_traits_declared<T>::value && 
+                 type_traits::is_list_like<T>::value &&
+                 !type_traits::is_back_insertable<T>::value &&
+                 type_traits::is_insertable<T>::value 
+    >::type>
+    {
+        using value_type = typename T::value_type;
+
+        template <class Json,class TempAllocator>
+        static T decode(basic_staj_cursor<CharT>& cursor, 
+                        json_decoder<Json,TempAllocator>& decoder, 
+                        std::error_code& ec)
+        {
+            T v;
+
+            cursor.array_expected(ec);
+            if (ec)
+            {
+                return T{};
+            }
+            if (cursor.current().event_type() != staj_event_type::begin_array)
+            {
+                ec = conv_errc::not_vector;
+                return v;
+            }
+            if (cursor.current().size() > 0)
+            {
+                reserve_storage(typename std::integral_constant<bool, type_traits::has_reserve<T>::value>::type(), v, cursor.current().size());
+            }
+            cursor.next(ec);
+            while (cursor.current().event_type() != staj_event_type::end_array && !ec)
+            {
+                v.insert(decode_traits<value_type,CharT>::decode(cursor, decoder, ec));
+                if (ec) {return T{};}
+                cursor.next(ec);
+                if (ec) {return T{};}
+            }
+            return v;
+        }
+
+        static void reserve_storage(std::true_type, T& v, std::size_t new_cap)
+        {
+            v.reserve(new_cap);
+        }
+
+        static void reserve_storage(std::false_type, T&, std::size_t)
+        {
+        }
+    };
+
+    // std::array
+
+    template <class T, class CharT, std::size_t N>
+    struct decode_traits<std::array<T,N>,CharT>
+    {
+        using value_type = typename std::array<T,N>::value_type;
+
+        template <class Json,class TempAllocator>
+        static std::array<T, N> decode(basic_staj_cursor<CharT>& cursor, 
+                                       json_decoder<Json,TempAllocator>& decoder, 
+                                       std::error_code& ec)
+        {
+            std::array<T,N> v;
+            cursor.array_expected(ec);
+            if (ec)
+            {
+                v.fill(T());
+                return v;
+            }
+            v.fill(T{});
+            if (cursor.current().event_type() != staj_event_type::begin_array)
+            {
+                ec = conv_errc::not_vector;
+                return v;
+            }
+            cursor.next(ec);
+            for (std::size_t i = 0; i < N && cursor.current().event_type() != staj_event_type::end_array && !ec; ++i)
+            {
+                v[i] = decode_traits<value_type,CharT>::decode(cursor, decoder, ec);
+                if (ec) {return v;}
+                cursor.next(ec);
+                if (ec) {return v;}
+            }
+            return v;
+        }
+    };
+
+    // map like
+
+    template <class T, class CharT>
+    struct decode_traits<T,CharT,
+        typename std::enable_if<!is_json_type_traits_declared<T>::value && 
+                                type_traits::is_map_like<T>::value &&
+                                type_traits::is_constructible_from_const_pointer_and_size<typename T::key_type>::value
+    >::type>
+    {
+        using mapped_type = typename T::mapped_type;
+        using value_type = typename T::value_type;
+        using key_type = typename T::key_type;
+
+        template <class Json,class TempAllocator>
+        static T decode(basic_staj_cursor<CharT>& cursor, 
+                        json_decoder<Json,TempAllocator>& decoder, 
+                        std::error_code& ec)
+        {
+            T val;
+            if (cursor.current().event_type() != staj_event_type::begin_object)
+            {
+                ec = conv_errc::not_map;
+                return val;
+            }
+            if (cursor.current().size() > 0)
+            {
+                reserve_storage(typename std::integral_constant<bool, type_traits::has_reserve<T>::value>::type(), val, cursor.current().size());
+            }
+            cursor.next(ec);
+
+            while (cursor.current().event_type() != staj_event_type::end_object && !ec)
+            {
+                if (cursor.current().event_type() != staj_event_type::key)
+                {
+                    ec = json_errc::expected_key;
+                    return val;
+                }
+                auto key = cursor.current().template get<key_type>(ec);
+                if (ec) return val;
+                cursor.next(ec);
+                if (ec) return val;
+                val.emplace(std::move(key),decode_traits<mapped_type,CharT>::decode(cursor, decoder, ec));
+                if (ec) {return val;}
+                cursor.next(ec);
+                if (ec) {return val;}
+            }
+            return val;
+        }
+
+        static void reserve_storage(std::true_type, T& v, std::size_t new_cap)
+        {
+            v.reserve(new_cap);
+        }
+
+        static void reserve_storage(std::false_type, T&, std::size_t)
+        {
+        }
+    };
+
+    template <class T, class CharT>
+    struct decode_traits<T,CharT,
+        typename std::enable_if<!is_json_type_traits_declared<T>::value && 
+                                type_traits::is_map_like<T>::value &&
+                                std::is_integral<typename T::key_type>::value
+    >::type>
+    {
+        using mapped_type = typename T::mapped_type;
+        using value_type = typename T::value_type;
+        using key_type = typename T::key_type;
+
+        template <class Json,class TempAllocator>
+        static T decode(basic_staj_cursor<CharT>& cursor, 
+                        json_decoder<Json,TempAllocator>& decoder, 
+                        std::error_code& ec)
+        {
+            T val;
+            if (cursor.current().event_type() != staj_event_type::begin_object)
+            {
+                ec = conv_errc::not_map;
+                return val;
+            }
+            if (cursor.current().size() > 0)
+            {
+                reserve_storage(typename std::integral_constant<bool, type_traits::has_reserve<T>::value>::type(), val, cursor.current().size());
+            }
+            cursor.next(ec);
+
+            while (cursor.current().event_type() != staj_event_type::end_object && !ec)
+            {
+                if (cursor.current().event_type() != staj_event_type::key)
+                {
+                    ec = json_errc::expected_key;
+                    return val;
+                }
+                auto s = cursor.current().template get<jsoncons::basic_string_view<typename Json::char_type>>(ec);
+                if (ec) return val;
+                key_type n{0};
+                auto r = jsoncons::detail::to_integer(s.data(), s.size(), n); 
+                if (r.ec != jsoncons::detail::to_integer_errc())
+                {
+                    ec = json_errc::invalid_number;
+                    return val;
+                }
+                cursor.next(ec);
+                if (ec) return val;
+                val.emplace(n, decode_traits<mapped_type,CharT>::decode(cursor, decoder, ec));
+                if (ec) {return val;}
+                cursor.next(ec);
+                if (ec) {return val;}
+            }
+            return val;
+        }
+
+        static void reserve_storage(std::true_type, T& v, std::size_t new_cap)
+        {
+            v.reserve(new_cap);
+        }
+
+        static void reserve_storage(std::false_type, T&, std::size_t)
+        {
+        }
+    };
+
+} // jsoncons
+
+#endif
+
-- 
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