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.h

@@ -0,0 +1,70 @@
+#ifndef IFC_TOKEN_H_
+#define IFC_TOKEN_H_
+
+#include "file-span.h"
+
+#include <blue/core/queue.h>
+
+#define TOKEN_TYPE(tok)     ((tok) ? (tok)->tok_type : TOK_NONE)
+#define TOKEN_IS(tok, type) ((tok) && ((tok)->tok_type & (type)) != 0)
+#define TOKEN_IS_SYMBOL(tok, sym)                                              \
+	((tok) && (tok)->tok_type == TOK_SYMBOL && (tok)->tok_sym == (sym))
+
+enum token_type {
+	TOK_NONE = 0,
+	TOK_SYMBOL = 0x0001u,
+	TOK_KEYWORD = 0x0002u,
+	TOK_WORD = 0x0004u,
+	TOK_NAME = 0x0008u,
+	TOK_INT = 0x0010u,
+	TOK_STRING = 0x0020u,
+	__TOK_UBOUND = 0x0040u,
+};
+
+enum token_value_type {
+	TOK_V_NONE = 0,
+	TOK_V_INT,
+	TOK_V_STRING,
+	TOK_V_SYMBOL,
+	TOK_V_KEYWORD,
+};
+
+enum token_symbol {
+	SYM_NONE = 0,
+	SYM_COMMA = __TOK_UBOUND,
+	SYM_HYPHEN,
+	SYM_SEMICOLON,
+	SYM_LEFT_BRACE,
+	SYM_RIGHT_BRACE,
+	SYM_LEFT_PAREN,
+	SYM_RIGHT_PAREN,
+	SYM_HYPHEN_RIGHT_ANGLE,
+	__SYM_UBOUND,
+};
+
+enum token_keyword {
+	KW_NONE = 0,
+	KW_INTERFACE = __SYM_UBOUND,
+	KW_MSG,
+};
+
+struct token {
+	struct file_span tok_location;
+	enum token_type tok_type;
+	enum token_value_type tok_value_type;
+	b_queue_entry tok_entry;
+
+	union {
+		char *tok_str;
+		enum token_symbol tok_sym;
+		enum token_keyword tok_kw;
+		long long tok_int;
+	};
+};
+
+extern void token_destroy(struct token *tok);
+extern const char *token_type_to_string(enum token_type type);
+extern const char *token_symbol_to_string(enum token_symbol sym);
+extern const char *token_keyword_to_string(enum token_keyword kw);
+
+#endif