Add basic AST functionality

src/ast.h

@@ -0,0 +1,109 @@
+#ifndef INCLUDE_SRC_AST_H_
+#define INCLUDE_SRC_AST_H_
+
+#include "error.h"
+#include "lexer.h"
+#include "tokenlist.h"
+#include <stddef.h>
+#include <stdint.h>
+
+typedef enum node_id {
+    NODE_INVALID,
+
+    NODE_PROGRAM,
+    NODE_STATEMENT,
+    NODE_LABEL,
+    NODE_DIRECTIVE,
+    NODE_INSTRUCTION,
+    NODE_OPERANDS,
+    NODE_OPERAND,
+    NODE_IMMEDIATE,
+    NODE_MEMORY,
+    NODE_NUMBER,
+    NODE_LABEL_REFERENCE,
+    NODE_MEMORY_EXPRESSION,
+    NODE_REGISTER_EXPRESSION,
+    NODE_REGISTER_INDEX,
+    NODE_REGISTER_OFFSET,
+    NODE_PLUS_OR_MINUS,
+    NODE_SECTION_DIRECTIVE,
+
+    // Validated primitives
+    NODE_REGISTER,
+    NODE_SECTION,
+
+    // Primitive nodes
+    NODE_IDENTIFIER,
+    NODE_DECIMAL,
+    NODE_HEXADECIMAL,
+    NODE_OCTAL,
+    NODE_BINARY,
+    NODE_CHAR,
+    NODE_STRING,
+    NODE_COLON,
+    NODE_COMMA,
+    NODE_LBRACKET,
+    NODE_RBRACKET,
+    NODE_PLUS,
+    NODE_MINUS,
+    NODE_ASTERISK,
+    NODE_DOT,
+} node_id_t;
+
+typedef struct ast_node ast_node_t;
+
+constexpr size_t node_default_children_cap = 8;
+/* 65K ought to be enough for anybody */
+constexpr size_t node_max_children_cap = 1 << 16;
+
+struct ast_node {
+    node_id_t id;
+    tokenlist_entry_t *token_entry;
+    size_t len;
+    size_t cap;
+    ast_node_t **children;
+
+    union {
+        struct {
+            uint64_t value;
+            int size;
+        } integer;
+        char *name;
+    } value;
+};
+
+/**
+ * @brief Allocates a new AST node
+ *
+ * Creates and initializes a new AST node with default (zero) values.
+ *
+ * @param[out] output Pointer to store the allocated node
+ * @return error_t* nullptr on success, allocation error on failure
+ */
+error_t *ast_node_alloc(ast_node_t **node);
+
+/**
+ * @brief Frees an AST node and all its children recursively
+ *
+ * Recursively frees all children of the node, then frees the node itself.
+ * If node is nullptr, the function returns without doing anything.
+ *
+ * @param node The node to free
+ */
+void ast_node_free(ast_node_t *node);
+
+/**
+ * @brief Adds a child node to a parent node
+ *
+ * Adds the specified child node to the parent's children array.
+ * If this is the first child, the function allocates the children array.
+ * If the children array is full, the function increases its capacity.
+ *
+ * @param node The parent node to add the child to
+ * @param child The child node to add
+ * @return error_t* nullptr on success, allocation error on failure,
+ *                  or err_node_children_cap if maximum capacity is reached
+ */
+error_t *ast_node_add_child(ast_node_t *node, ast_node_t *child);
+
+#endif // INCLUDE_SRC_AST_H_