quip: Add initial lexer sources + example ref

Signed-off-by: Ian Moffett <ian@mirocom.org>

example/ref.quip

@@ -0,0 +1,19 @@
+.cc clang
+.ld   lld-link
+
+CFLAGS ::
+     -Iinclude/
+     -mgeneral-regs-only
+     -ffreestanding
+      $CONF  # expands to -D chain
+~
+
+.obiter echo $OBJ
+.obiter objcopy -O binary $OBJ $OBJ.bin
+.oblink
+
+# configuration section
+# these get
+
+conf FOO  : true
+conf BAR  : 123

frontend/lexer.c

@@ -0,0 +1,127 @@
+/*
+ * Copyright (c) 2026, Mirocom Laboratories
+ * Provided under the BSD-3 clause
+ *
+ * Abstract:
+ *      This file implements the lexer.
+ * Author:
+ *      Ian M. Moffett <ian@mirocom.org>
+ */
+
+#include <sys/types.h>
+#include <stddef.h>
+#include <stdbool.h>
+#include <unistd.h>
+#include <errno.h>
+#include <ctype.h>
+#include "frontend/token.h"
+#include "frontend/lexer.h"
+
+/*
+ * Test if a given character counts as a whitespace character
+ *
+ * @c: Character to test
+ */
+static inline bool
+lexer_is_ws(char c)
+{
+    switch (c) {
+    case '\t':
+    case '\f':
+    case '\a':
+    case ' ':
+        return true;
+    }
+
+    return false;
+}
+
+/*
+ * Consume a single character in a buffered manner from the
+ * build source file.
+ *
+ * @state: Quip state machine
+ *
+ * Returns the fetched character on success, otherwise a value
+ * of '\0' on failure.
+ */
+static char
+lexer_buffer_consume(struct quip_state *state)
+{
+    ssize_t n;
+
+    if (state == NULL) {
+        return '\0';
+    }
+
+    /*
+     * If there is nothing in the lexer-side buffer, fill it
+     * with what we can.
+     */
+    if (state->lex_buf_cap == 0) {
+        n = read(state->in_fd, state->lex_buf, LEX_FILEBUF_LEN);
+        if (n <= 0)
+            return '\0';
+
+        state->lex_buf_cap = n;
+    }
+
+    /* Grab a single character if not empty */
+    if (state->lex_buf_i < state->lex_buf_cap) {
+        return state->lex_buf[state->lex_buf_i++];
+    }
+
+    /* Empty, reset everything and try again */
+    state->lex_buf_cap = 0;
+    state->lex_buf_i = 0;
+    return lexer_buffer_consume(state);
+}
+
+/*
+ * Consume a single character optionally skipping whitespace
+ *
+ * @state:    Quip state machine
+ * @skip_ws: If true, skip whitespace
+ */
+static char
+lexer_consume(struct quip_state *state, bool skip_ws)
+{
+    char c;
+
+    while ((c = lexer_buffer_consume(state)) != '\0') {
+        if (skip_ws && lexer_is_ws(c)) {
+            continue;
+        }
+
+        return c;
+    }
+
+    return '\0';
+}
+
+int
+lexer_scan(struct quip_state *state, struct token *tokres)
+{
+    char c;
+
+    if (state == NULL || tokres == NULL) {
+        return -1;
+    }
+
+    if ((c = lexer_consume(state, true)) == '\0') {
+        return -1;
+    }
+
+    switch (c) {
+    case '\n':
+        tokres->type = TT_NEWLINE;
+        tokres->c = c;
+        return 0;
+    case ':':
+        tokres->type = TT_COLON;
+        tokres->c = c;
+        return 0;
+    }
+
+    return -1;
+}

include/common/knobs.h

@@ -11,7 +11,11 @@
 #ifndef COMMON_KNOBS_H
 #define COMMON_KNOBS_H 1
 
+/* Core settings */
 #define QUIP_VERSION "0.0.1"
 #define QUIP_FILEPATH "build.quip"
 
+/* Buffering settings */
+#define LEX_FILEBUF_LEN 16
+
 #endif  /* !_COMMON_KNOBS_H_ */

include/common/state.h

@@ -13,16 +13,23 @@
 
 #include <stdint.h>
 #include <stddef.h>
+#include "common/knobs.h"
 
 /*
  * Represents the build state machine
  *
- * @in_fd:      Input file descriptor of build  file
- * @line_num:   Current line number
+ * @in_fd:          Input file descriptor of build  file
+ * @line_num:       Current line number
+ * @lex_buf:        Used to reduce system call frequency
+ * @lex_buf_cap:    Lexer buffer capacity
+ * @lex_buf_i:      Lexer buffer index
  */
 struct quip_state {
     int in_fd;
     size_t line_num;
+    char lex_buf[LEX_FILEBUF_LEN];
+    size_t lex_buf_cap;
+    size_t lex_buf_i;
 };
 
 /*

include/frontend/lexer.h

@@ -0,0 +1,19 @@
+#ifndef FRONTEND_LEXER_H
+#define FRONTEND_LEXER_H 1
+
+#include <stdint.h>
+#include <stddef.h>
+#include "frontend/token.h"
+#include "common/state.h"
+
+/*
+ * Scan for a single token within the source file
+ *
+ * @state:   Quip state
+ * @tokres:  Token result is written here
+ *
+ * Returns zero on success
+ */
+int lexer_scan(struct quip_state *state, struct token *tokres);
+
+#endif  /* !FRONTEND_LEXER_H */

include/frontend/token.h

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2026, Mirocom Laboratories
+ * Provided under the BSD-3 clause
+ *
+ * Abstract:
+ *      This file defines the list of valid tokens.
+ * Author:
+ *      Ian M. Moffett <ian@mirocom.org>
+ */
+
+#ifndef FRONTEND_TOKEN_H
+#define FRONTEND_TOKEN_H 1
+
+/*
+ * Represents valid token types
+ */
+typedef enum {
+    TT_NONE,        /* [none] */
+    TT_NAME,        /* [name] */
+    TT_NEWLINE,     /* [newline] */
+    TT_COLON,       /* ':' */
+} tt_t;
+
+/*
+ * Represents a lexical token
+ *
+ * @type: Token type
+ */
+struct token {
+    tt_t type;
+    union {
+        char c;
+    };
+};
+
+#endif  /* !FRONTEND_TOKEN_H */