ast: Create AST visitor to traverse the tree

In the future we want to have the possibility of traverse the tree and
pretty print it or generate binary for other platform like LLVM or
transpile to C.

This solution also implements the gas assembly x86_64 Linux code
generation by using the visitor interface.

Signed-off-by: Johnny Richard <johnny@johnnyrichard.com>

1 files changed, 57 insertions, 0 deletions

diff --git a/src/ast.h b/src/ast.h
new file mode 100644
index 0000000..7f5a198
--- /dev/null
+++ b/src/ast.h
@@ -0,0 +1,57 @@
+/*
+* Copyright (C) 2023 Johnny Richard
+*
+* This program is free software: you can redistribute it and/or modify
+* it under the terms of the GNU General Public License as published by
+* the Free Software Foundation, either version 3 of the License, or
+* (at your option) any later version.
+*
+* This program is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+* GNU General Public License for more details.
+*
+* You should have received a copy of the GNU General Public License
+* along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+#ifndef AST_H
+#define AST_H
+#include <stdint.h>
+#include "string_view.h"
+
+#define ast_visitor_visit(visitor, node) ast_node_accept_visitor((ast_node_t *) node, (ast_visitor_t *) visitor);
+
+typedef enum {
+  TYPE_I32
+} type_t;
+
+typedef struct ast_visitor_t ast_visitor_t;
+
+typedef struct ast_node_t {
+  void (*accept_visitor)(struct ast_node_t *, ast_visitor_t *);
+} ast_node_t;
+
+typedef struct ast_return_stmt_t {
+  struct ast_node_t super;
+  uint32_t number;
+} ast_return_stmt_t;
+
+typedef struct ast_function_t {
+  struct ast_node_t super;
+  string_view_t name;
+  type_t  return_type;
+  ast_return_stmt_t body;
+} ast_function_t;
+
+typedef struct ast_visitor_t {
+  void (*visit_function)(struct ast_visitor_t *, ast_function_t *);
+  void (*visit_return_stmt)(struct ast_visitor_t *, ast_return_stmt_t *);
+} ast_visitor_t;
+
+void ast_node_accept_visitor(ast_node_t *node, ast_visitor_t *visitor);
+
+ast_function_t ast_function_create(string_view_t name, type_t return_type, ast_return_stmt_t body);
+ast_return_stmt_t ast_return_stmt_create(uint32_t number);
+
+#endif /* AST_H */
+