feat: implement AST walker

include/compiler/fzl_walker.h

@@ -0,0 +1,34 @@
+#ifndef FZL_WALKER_H
+#define FZL_WALKER_H
+
+#include <common/fzl_opcodes.h>
+#include <compiler/fzl_parser.h>
+#include <compiler/utils/fzl_const_pool.h>
+#include <stddef.h>
+
+// Walker descriptor
+typedef struct
+{
+  fzl_node_t *root;
+  fzl_const_hash_pool_t *consts;
+
+  uint64_t *ops;
+  size_t op_count;
+  size_t op_remainder;
+} fzl_walker_t;
+
+// Allocate new walker
+fzl_walker_t *fzl_mkwalker(fzl_node_t *root);
+
+// Walk throught the entire AST and build:
+// 1. Constants table
+// 2. Operations
+int fzl_walk(fzl_walker_t *walker);
+
+// Get last error message
+char *fzl_walker_geterror();
+
+// Free walker
+void fzl_freewalker(fzl_walker_t *walker);
+
+#endif // FZL_WALKER_H