From f58f206b7f4f6bf7eb67a3001083e97835dc0acc Mon Sep 17 00:00:00 2001
From: qicosmos <qicosmos@163.com>
Date: Wed, 27 Nov 2024 14:27:03 +0800
Subject: [PATCH] support span

---
 iguana/detail/traits.hpp | 16 ++++++++++++++++
 iguana/json_reader.hpp   | 14 +++++++++++++-
 iguana/util.hpp          |  8 +++++++-
 test/unit_test.cpp       | 17 +++++++++++++++++
 4 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/iguana/detail/traits.hpp b/iguana/detail/traits.hpp
index a51941f8..062e1fb6 100644
--- a/iguana/detail/traits.hpp
+++ b/iguana/detail/traits.hpp
@@ -14,6 +14,12 @@
 #include <variant>
 #include <vector>
 
+#if __cplusplus > 201703L
+#if __has_include(<span>)
+#include <span>
+#endif
+#endif
+
 #include "iguana/define.h"
 
 namespace iguana {
@@ -40,6 +46,16 @@ struct is_stdstring : is_template_instant_of<std::basic_string, T> {};
 template <typename T>
 struct is_tuple : is_template_instant_of<std::tuple, T> {};
 
+#if __cplusplus > 201703L
+#if __has_include(<span>)
+template <typename>
+struct is_span : std::false_type {};
+
+template <typename T, size_t Extent>
+struct is_span<std::span<T, Extent>> : std::true_type {};
+#endif
+#endif
+
 template <class T>
 struct is_sequence_container
     : std::integral_constant<
diff --git a/iguana/json_reader.hpp b/iguana/json_reader.hpp
index 1485f2bb..768610dc 100644
--- a/iguana/json_reader.hpp
+++ b/iguana/json_reader.hpp
@@ -265,10 +265,22 @@ IGUANA_INLINE void from_json_impl(U &value, It &&it, It &&end) {
   }
 }
 
+template <typename T>
+constexpr size_t get_array_size(const T &t) {
+#if __cplusplus > 201703L
+#if __has_include(<span>)
+  if constexpr (is_span<T>::value)
+    return t.size();
+  else
+#endif
+#endif
+    return sizeof(T) / sizeof(decltype(std::declval<T>()[0]));
+}
+
 template <typename U, typename It, std::enable_if_t<fixed_array_v<U>, int> = 0>
 IGUANA_INLINE void from_json_impl(U &value, It &&it, It &&end) {
   using T = std::remove_reference_t<U>;
-  constexpr auto n = sizeof(T) / sizeof(decltype(std::declval<T>()[0]));
+  size_t n = get_array_size(value);
   skip_ws(it, end);
 
   if constexpr (std::is_same_v<char, std::remove_reference_t<
diff --git a/iguana/util.hpp b/iguana/util.hpp
index 75a4874d..dae562f0 100644
--- a/iguana/util.hpp
+++ b/iguana/util.hpp
@@ -89,7 +89,13 @@ template <typename T>
 constexpr inline bool array_v = is_array<std::remove_cvref_t<T>>::value;
 
 template <typename Type>
-constexpr inline bool fixed_array_v = c_array_v<Type> || array_v<Type>;
+constexpr inline bool fixed_array_v = c_array_v<Type> ||
+#if __cplusplus > 201703L
+#if __has_include(<span>)
+                                      is_span<Type>::value ||
+#endif
+#endif
+                                      array_v<Type>;
 
 template <typename T>
 constexpr inline bool string_view_v =
diff --git a/test/unit_test.cpp b/test/unit_test.cpp
index 92d265b4..c0bd2a1e 100644
--- a/test/unit_test.cpp
+++ b/test/unit_test.cpp
@@ -95,6 +95,23 @@ TEST_CASE("test parse item array_t") {
     CHECK(test[0] == 1);
     CHECK(test[1] == -222);
   }
+#if __cplusplus > 201703L
+#if __has_include(<span>)
+  {
+    std::vector<int> v{1, 2};
+    std::span<int> span(v);
+    std::string str;
+    iguana::to_json(span, str);
+
+    std::vector<int> v1;
+    v1.resize(2);
+    std::span<int> span1(v1);
+
+    iguana::from_json(span1, str);
+    CHECK(v == v1);
+  }
+#endif
+#endif
   {
     std::string str{"[1, -222,"};
     std::array<int, 2> test;