Add basic compilation database parsing

include/cppast/libclang_parser.hpp

@@ -25,6 +25,50 @@ namespace cppast
         };
     } // namespace detail
 
+    /// The exception thrown when a fatal parse error occurs.
+    class libclang_error final : public std::runtime_error
+    {
+    public:
+        /// \effects Creates it with a message.
+        libclang_error(std::string msg) : std::runtime_error(std::move(msg))
+        {
+        }
+    };
+
+    /// A compilation database.
+    ///
+    /// This represents a `compile_commands.json` file,
+    /// which stores all the commands needed to compile a set of files.
+    /// It can be generated by CMake using the `CMAKE_EXPORT_COMPILE_COMMANDS` option.
+    class libclang_compilation_database
+    {
+    public:
+        /// \effects Creates it giving the directory where the `compile_commands.json` file is located.
+        /// \throws `libclang_error` if the database could not be loaded or found.
+        libclang_compilation_database(const std::string& build_directory);
+
+        libclang_compilation_database(libclang_compilation_database&& other)
+        : database_(other.database_)
+        {
+            other.database_ = nullptr;
+        }
+
+        ~libclang_compilation_database();
+
+        libclang_compilation_database& operator=(libclang_compilation_database&& other)
+        {
+            libclang_compilation_database tmp(std::move(other));
+            std::swap(tmp.database_, database_);
+            return *this;
+        }
+
+    private:
+        using database = void*;
+        database database_;
+
+        friend libclang_compile_config;
+    };
+
     /// Compilation config for the [cppast::libclang_parser]().
     class libclang_compile_config final : public compile_config
     {
@@ -36,6 +80,20 @@ namespace cppast
         /// It will also define `__cppast__` with the value `"libclang"` as well as `__cppast_major__` and `__cppast_minor__`.
         libclang_compile_config();
 
+        /// Creates the configuration stored in the database.
+        ///
+        /// \effects It will use the options found in the database for the specified file.
+        /// This does not necessarily need to match the file that is going to be parsed,
+        /// but it should.
+        /// It will also add the default configuration options.
+        /// \notes Header files are not included in the compilation database,
+        /// you need to pass in the file name of the corresponding source file,
+        /// if you want to parse one.
+        /// \notes It will only consider options you could also set by the other functions.
+        /// \notes The file key will include the specified directory in the JSON, if it is not a full path.
+        libclang_compile_config(const libclang_compilation_database& database,
+                                const std::string&                   file);
+
         /// \effects Sets the path to the location of the `clang++` binary and the version of that binary.
         /// \notes It will be used for preprocessing.
         void set_clang_binary(std::string binary, int major, int minor, int patch)
@@ -64,16 +122,6 @@ namespace cppast
         friend detail::libclang_compile_config_access;
     };
 
-    /// The exception thrown when a fatal parse error occurs.
-    class libclang_error final : public std::runtime_error
-    {
-    public:
-        /// \effects Creates it with a message.
-        libclang_error(std::string msg) : std::runtime_error(std::move(msg))
-        {
-        }
-    };
-
     /// A parser that uses libclang.
     class libclang_parser final : public parser
     {