3 files changed, 100 insertions, 0 deletions
diff --git a/head/defconf/lexer.h b/head/defconf/lexer.h
new file mode 100644
index 0000000..6fb3828
--- /dev/null
+++ b/head/defconf/lexer.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2026, Apollo Telephone Laboratories.
+ * Provided under the BSD-3 clause.
+ */
+
+#ifndef DEFCONF_LEXER_H
+#define DEFCONF_LEXER_H 1
+
+#include <stdint.h>
+#include "defconf/token.h"
+#include "defconf/state.h"
+
+/*
+ * Scan for a single token
+ *
+ * @state:  Defconf state machine
+ * @result: Result is written here
+ *
+ * Returns zero
+ */
+int lexer_scan(struct defconf_state *state, struct token *result);
+
+#endif  /* !_DEFCONF_LEXER_H_ */
diff --git a/head/defconf/state.h b/head/defconf/state.h
new file mode 100644
index 0000000..524af3b
--- /dev/null
+++ b/head/defconf/state.h
@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2026, Apollo Telephone Laboratories.
+ * Provided under the BSD-3 clause.
+ */
+
+#ifndef DEFCONF_STATE_H
+#define DEFCONF_STATE_H 1
+
+#include <stdint.h>
+#include <stddef.h>
+#include <stdio.h>
+
+/*
+ * DEFCONF state machine
+ *
+ * @in_fp:      Input file pointer
+ * @lex_cache:  Putback cache
+ */
+struct defconf_state {
+    FILE *in_fp;
+    int lex_cache;
+};
+
+/*
+ * Initialize the defconf state machine
+ *
+ * @in_path:  Input path
+ * @state:    State machine result
+ *
+ * Returns zero on success
+ */
+int defconf_state_init(const char *in_path, struct defconf_state *state);
+
+/*
+ * Destroy the defconf state machine
+ *
+ * @state:  State machine to destroy
+ */
+void defconf_state_destroy(struct defconf_state *state);
+
+#endif  /* !DEFCONF_STATE_H */
diff --git a/head/defconf/token.h b/head/defconf/token.h
new file mode 100644
index 0000000..e1abd0a
--- /dev/null
+++ b/head/defconf/token.h
@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2026, Apollo Telephone Laboratories.
+ * Provided under the BSD-3 clause.
+ */
+
+#ifndef DEFCONF_TOKEN_H
+#define DEFCONF_TOKEN_H 1
+
+/*
+ * Valid token types
+ */
+typedef enum {
+    TT_NONE,        /* [none] */
+    TT_DEFINE,      /* 'define' */
+    TT_TRUE,        /* 'true' */
+    TT_FALSE,       /* 'false' */
+    TT_INTLIT,      /* [0-9]+ */
+    TT_IDENT,       /* [ident] */
+} tt_t;
+
+/*
+ * Represents a token
+ *
+ * @type:  Token type
+ * @c:     Associated character
+ * @s:     Associated string
+ */
+struct token {
+    tt_t type;
+    union {
+        char c;
+        char *s;
+    };
+};
+
+#endif  /* !DEFCONF_TOKEN_H */