toolchain: add a program for compiling ipc interface definitions

ifc can be used to compile .if files into self-contained header-only C
libraries, which can be used to send/receive messages that conform
to the described interface.

toolchain/ifc/token.c

@@ -0,0 +1,63 @@
+#include "token.h"
+
+void token_destroy(struct token *tok)
+{
+	switch (tok->tok_value_type) {
+	case TOK_V_STRING:
+		if (tok->tok_str) {
+			free(tok->tok_str);
+		}
+		break;
+	default:
+		break;
+	}
+
+	free(tok);
+}
+
+#define ENUM_STR(x)                                                            \
+	case x:                                                                \
+		return #x
+
+const char *token_type_to_string(enum token_type type)
+{
+	switch (type) {
+		ENUM_STR(TOK_NONE);
+		ENUM_STR(TOK_INT);
+		ENUM_STR(TOK_SYMBOL);
+		ENUM_STR(TOK_WORD);
+		ENUM_STR(TOK_NAME);
+		ENUM_STR(TOK_STRING);
+		ENUM_STR(TOK_KEYWORD);
+	default:
+		return "";
+	}
+}
+
+const char *token_symbol_to_string(enum token_symbol sym)
+{
+	switch (sym) {
+		ENUM_STR(SYM_NONE);
+		ENUM_STR(SYM_COMMA);
+		ENUM_STR(SYM_SEMICOLON);
+		ENUM_STR(SYM_HYPHEN);
+		ENUM_STR(SYM_LEFT_BRACE);
+		ENUM_STR(SYM_RIGHT_BRACE);
+		ENUM_STR(SYM_LEFT_PAREN);
+		ENUM_STR(SYM_RIGHT_PAREN);
+		ENUM_STR(SYM_HYPHEN_RIGHT_ANGLE);
+	default:
+		return "";
+	}
+}
+
+const char *token_keyword_to_string(enum token_keyword kw)
+{
+	switch (kw) {
+		ENUM_STR(KW_NONE);
+		ENUM_STR(KW_INTERFACE);
+		ENUM_STR(KW_MSG);
+	default:
+		return "";
+	}
+}