1 files changed, 58 insertions, 24 deletions

diff --git a/cursor.lisp b/cursor.lisp
index 72d4c90..a4cc100 100644
--- a/cursor.lisp
+++ b/cursor.lisp
@@ -1,40 +1,74 @@
 (in-package #:monparser)
 
-(defclass cursor ()
-  ((index :type (unsigned-byte 44) :initarg :index :accessor index :initform 0)
-   (data :type simple-string :initarg :data :reader data :initform "")))
+(defstruct cursor
+  (start 0 :type (unsigned-byte 44))
+  (end 0 :type (unsigned-byte 44))
+  (data "" :type simple-string))
 
-(defun has-data? (cursor)
-  (< (index cursor) (length (data cursor))))
+(declaim (ftype (function (cursor) boolean) cursor-has-data?))
+(defun cursor-has-data? (cursor)
+  (< (cursor-end cursor) (length (cursor-data cursor))))
 
-(defun peek (cursor)
-  (char (data cursor)
-        (index cursor)))
+(declaim (ftype (function (cursor) boolean) cursor-at-start?))
+(defun cursor-at-start? (cursor)
+  (= (cursor-start cursor) (cursor-end cursor)))
 
-(defun advance (cursor)
-  (make-instance 'cursor
-                 :data (data cursor)
-                 :index (+ (index cursor) 1)))
+(declaim (ftype (function (cursor) standard-char) cursor-peek))
+(defun cursor-peek (cursor)
+  (char (cursor-data cursor)
+        (cursor-end cursor)))
 
+(declaim (ftype (function (cursor) cursor) cursor-advance))
+(defun cursor-advance (cursor)
+  (make-cursor :data (cursor-data cursor)
+               :start (cursor-start cursor)
+               :end (+ (cursor-end cursor) 1)))
+
+(declaim (ftype (function (cursor) cursor) cursor-rebase))
+(defun cursor-rebase (cursor)
+  (make-cursor :data (cursor-data cursor)
+               :start (cursor-end cursor)
+               :end (cursor-end cursor)))
+
+(declaim (ftype (function (cursor cursor) cursor) cursor-merge))
+(defun cursor-merge (prev next)
+  (assert (eq (cursor-data prev) (cursor-data next)))
+  (make-cursor :data (cursor-data next)
+               :start (cursor-start prev)
+               :end (cursor-end next)))
+
+(declaim (ftype (function (cursor cursor) fixnum) distance))
 (defun distance (from to)
-  (- (index to)
-     (index from)))
+  (assert (eq (cursor-data from) (cursor-data to)))
+  (- (cursor-end to)
+     (cursor-end from)))
 
-(defun context-window (str index &key (side-length 20))
-  (let ((begin (max (- index side-length) 0))
-        (end (min (+ index side-length) (length str)))
+(declaim (ftype (function (cursor &key (:side-length fixnum)) t) context-window))
+(defun context-window (cursor &key (side-length 20))
+  (let ((begin (max (- (cursor-start cursor) side-length) 0))
+        (end (min (+ (cursor-end cursor) side-length) (length (cursor-data cursor))))
         (result '()))
-    (push (subseq str (1+ index) end) result)
-    (push (elt str index) result)
-    (push (subseq str begin index) result)
+    (push (subseq (cursor-data cursor) (cursor-end cursor) end) result)
+    (push (subseq (cursor-data cursor) (cursor-start cursor) (cursor-end cursor)) result)
+    (push (subseq (cursor-data cursor) begin (cursor-start cursor)) result)
     result))
 
+(declaim (ftype (function (cursor) (cons fixnum fixnum)) line-and-column))
+(defun line-and-column (cursor)
+  (let ((line 1) (column 1))
+    (dotimes (i (cursor-end cursor))
+      (let ((c (char (cursor-data cursor) i)))
+        (case c
+          (#\Newline
+           (incf line)
+           (setf column 1))
+          (t (incf column)))))
+    (cons line column)))
+
 (defmethod print-object ((obj cursor) stream)
   (print-unreadable-object (obj stream :type t)
-    (let ((str (if (has-data? obj)
+    (let ((str (if (cursor-has-data? obj)
                  (format nil "~{~a~a~a~}"
-                         (context-window (data obj)
-                                         (index obj)
-                                         :side-length 10))
+                         (context-window obj :side-length 10))
                  "END OF DATA")))
       (format stream "~s" (substitute #\~ #\Newline str)))))