Merge pull request #1392 from mtalliance/feature/addFileInputAdapter

Feature/add file input adapter

include/nlohmann/detail/input/input_adapters.hpp

@@ -10,6 +10,7 @@
 #include <string> // string, char_traits
 #include <type_traits> // enable_if, is_base_of, is_pointer, is_integral, remove_pointer
 #include <utility> // pair, declval
+#include <cstdio> //FILE *
 
 #include <nlohmann/detail/macro_scope.hpp>
 
@@ -45,6 +46,27 @@ struct input_adapter_protocol
 /// a type to simplify interfaces
 using input_adapter_t = std::shared_ptr<input_adapter_protocol>;
 
+/*!
+Input adapter for stdio file access. This adapter read only 1 byte and do not use any
+ buffer. This adapter is a very low level adapter.
+*/
+class file_input_adapter : public input_adapter_protocol
+{
+  public:
+    explicit file_input_adapter(std::FILE* f)  noexcept
+        : m_file(f)
+    {}
+
+    std::char_traits<char>::int_type get_character() noexcept override
+    {
+        return std::fgetc(m_file);
+    }
+  private:
+    /// the file pointer to read from
+    std::FILE* m_file;
+};
+
+
 /*!
 Input adapter for a (caching) istream. Ignores a UFT Byte Order Mark at
 beginning of input. Does not support changing the underlying std::streambuf
@@ -293,7 +315,8 @@ class input_adapter
 {
   public:
     // native support
-
+    input_adapter(std::FILE* file)
+        : ia(std::make_shared<file_input_adapter>(file)) {}
     /// input adapter for input stream
     input_adapter(std::istream& i)
         : ia(std::make_shared<input_stream_adapter>(i)) {}

single_include/nlohmann/json.hpp

@@ -2058,6 +2058,7 @@ constexpr const auto& to_json = detail::static_const<detail::to_json_fn>::value;
 #include <string> // string, char_traits
 #include <type_traits> // enable_if, is_base_of, is_pointer, is_integral, remove_pointer
 #include <utility> // pair, declval
+#include <cstdio> //FILE *
 
 // #include <nlohmann/detail/macro_scope.hpp>
 
@@ -2094,6 +2095,27 @@ struct input_adapter_protocol
 /// a type to simplify interfaces
 using input_adapter_t = std::shared_ptr<input_adapter_protocol>;
 
+/*!
+Input adapter for stdio file access. This adapter read only 1 byte and do not use any
+ buffer. This adapter is a very low level adapter.
+*/
+class file_input_adapter : public input_adapter_protocol
+{
+  public:
+    explicit file_input_adapter(std::FILE* f)  noexcept
+        : m_file(f)
+    {}
+
+    std::char_traits<char>::int_type get_character() noexcept override
+    {
+        return std::fgetc(m_file);
+    }
+  private:
+    /// the file pointer to read from
+    std::FILE* m_file;
+};
+
+
 /*!
 Input adapter for a (caching) istream. Ignores a UFT Byte Order Mark at
 beginning of input. Does not support changing the underlying std::streambuf
@@ -2342,7 +2364,8 @@ class input_adapter
 {
   public:
     // native support
-
+    input_adapter(std::FILE* file)
+        : ia(std::make_shared<file_input_adapter>(file)) {}
     /// input adapter for input stream
     input_adapter(std::istream& i)
         : ia(std::make_shared<input_stream_adapter>(i)) {}

test/src/unit-testsuites.cpp

@@ -384,6 +384,41 @@ TEST_CASE("json.org examples")
         json j;
         CHECK_NOTHROW(f >> j);
     }
+    SECTION("FILE 1.json")
+    {
+        std::unique_ptr<std::FILE, decltype(&std::fclose)> f(std::fopen("test/data/json.org/1.json", "r"), &std::fclose);
+        json j;
+        CHECK_NOTHROW(j.parse(f.get()));
+    }
+
+    SECTION("FILE 2.json")
+    {
+        std::unique_ptr<std::FILE, decltype(&std::fclose)> f(std::fopen("test/data/json.org/2.json", "r"), &std::fclose);
+        json j;
+        CHECK_NOTHROW(j.parse(f.get()));
+    }
+
+    SECTION("FILE 3.json")
+    {
+        std::unique_ptr<std::FILE, decltype(&std::fclose)> f(std::fopen("test/data/json.org/3.json", "r"), &std::fclose);
+        json j;
+        CHECK_NOTHROW(j.parse(f.get()));
+    }
+
+    SECTION("FILE 4.json")
+    {
+        std::unique_ptr<std::FILE, decltype(&std::fclose)> f(std::fopen("test/data/json.org/4.json", "r"), &std::fclose);
+        json j;
+        CHECK_NOTHROW(j.parse(f.get()));
+    }
+
+    SECTION("FILE 5.json")
+    {
+        std::unique_ptr<std::FILE, decltype(&std::fclose)> f(std::fopen("test/data/json.org/5.json", "r"), &std::fclose);
+        json j;
+        CHECK_NOTHROW(j.parse(f.get()));
+    }
+
 }
 
 TEST_CASE("RFC 7159 examples")