feat: implement AST walker

include/compiler/utils/fzl_const_pool.h

@@ -0,0 +1,64 @@
+#ifndef FZL_CONST_SET_H
+#define FZL_CONST_SET_H
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+// Constant types
+typedef enum
+{
+  FZL_CONSTTYPE_STRING
+} fzl_consttype_t;
+
+// Constant descriptor
+typedef struct
+{
+  fzl_consttype_t type;
+
+  union
+  {
+    struct
+    {
+      const char *chars;
+      size_t length;
+    } string;
+  } as;
+} fzl_const_t;
+
+typedef struct
+{
+  size_t pool_index;
+} fzl_const_hash_slot_t;
+
+// Constant pool descriptor
+typedef struct
+{
+  fzl_const_t *array;
+  size_t size;
+  size_t capacity;
+
+  fzl_const_hash_slot_t *slots;
+  size_t slots_count;
+  size_t slots_capacity;
+} fzl_const_hash_pool_t;
+
+// Compare two constants for equality
+bool fzl_consts_equal(fzl_const_t a, fzl_const_t b);
+
+// Get hash of specified constant
+static uint32_t fzl_hash_const(fzl_const_t c);
+
+// Allocate constants hash pool
+fzl_const_hash_pool_t *fzl_mkconstpool();
+
+// Resize the hash table
+static void fzl_consts_pool_resize_hash(fzl_const_hash_pool_t *pool);
+
+// Push constant. Returns unique index
+size_t fzl_consts_pool_add(fzl_const_hash_pool_t *pool, fzl_const_t c);
+
+// Free constants hash pool
+void fzl_consts_pool_free(fzl_const_hash_pool_t *pool);
+
+#endif // FZL_CONST_SET_H