From: plugd <plugd@thelambdalab.xyz>
Date: Sat, 11 Nov 2023 13:15:57 +0000 (+0100)
Subject: Dictionary lookup working.
X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?p=ez.git;a=commitdiff_plain;h=HEAD;hp=a437668aefaafa527eb913ae3f990381436347ab

Dictionary lookup working.
---

diff --git a/ez.el b/ez.el
index 95547d1..a6f1f9c 100644
--- a/ez.el
+++ b/ez.el
@@ -1,8 +1,8 @@
 ;;; ez.el --- Emacs Z-machine
 
-;; Copyright (C) 2021 Tim Vaughan
+;; Copyright (C) 2021,2022,2023 Tim Vaughan
 
-;; Author: Tim Vaughan <timv@ughan.xyz>
+;; Author: Tim Vaughan <plugd@thelambdalab.xyz>
 ;; Created: 13 Oct 2021
 ;; Version: 1.0
 ;; Keywords: game
@@ -26,6 +26,13 @@
 
 ;;; Commentary:
 
+;; There are many Z-machine interpreters, but this one is mine.
+;; It only capable of interpreting the subset of Z-code necessary
+;; to run the first Zork game in z3 format.
+;;
+;; It is based entirely on the description of the Z-machine contained
+;; Marnix Klooster's wonderful document, "The Z-machine And How to Emulate It."
+
 ;;; Code:
 
 ;; Utility functions
@@ -77,15 +84,33 @@
 (defvar ez-abbrevtab-addr nil)
 (defvar ez-globalvartab-addr nil)
 
+(defvar ez-dict-entries nil
+  "Parsed dictionary")
+
+(defvar ez-dict-separators nil
+  "Parsed dictionary")
+
 (defun ez-mem-ref-byte (addr)
   (aref ez-memory addr))
 
+(defun ez-mem-ref-bytes (addr count)
+  (mapcar (lambda (offset) (ez-mem-ref-byte (+ addr offset)))
+          (number-sequence 0 (- count 1))))
+
 (defun ez-mem-set-byte (addr val)
   (aset ez-memory addr val))
 
+(defun ez-mem-set-bytes (addr vals)
+  (dotimes (i (length vals))
+    (ez-mem-set-byte (+ addr i) (elt vals i))))
+
 (defun ez-mem-ref-word (addr)
-  (+ (* 256 (aref ez-memory addr))
-     (aref ez-memory (+ addr 1))))
+  (logior (lsh (aref ez-memory addr) 8)
+          (aref ez-memory (+ addr 1))))
+
+(defun ez-mem-ref-words (addr count)
+  (mapcar (lambda (offset) (ez-mem-ref-word (+ addr offset)))
+          (number-sequence 0 (- (* 2 count) 1) 2)))
 
 (defun ez-mem-set-word (addr val)
   (let ((byte-high (/ val 256))
@@ -93,6 +118,9 @@
     (aset ez-memory addr byte-high)
     (aset ez-memory (+ addr 1) byte-low)))
 
+(defun ez-mem-ref-string (addr1 addr2)
+  (substring ez-memory addr1 addr2))
+
 (defun ez-parse-header ()
   (setq ez-version (ez-mem-ref-byte #x0))
   (setq ez-himem-addr (ez-mem-ref-word #x4))
@@ -116,12 +144,12 @@
       (error "Invalid global variable %d" gvar))
   (let ((val
          (ez-mem-ref-word (+ (* 2 gvar) ez-globalvartab-addr))))
-    (message "\tRetrieved %x from global variable %x" val gvar)
+    (ez-debug-message "\tRetrieved %x from global variable %x" val gvar)
     val))
 
 (defun ez-set-global-var (gvar val)
   (ez-mem-set-word (+ (* 2 gvar) ez-globalvartab-addr) val)
-  (message "\tSet global variabl %x to %x" gvar val))
+  (ez-debug-message "\tSet global variabl %x to %x" gvar val))
 
 ;; Object tree
 
@@ -267,6 +295,12 @@
         (logand (lsh word -5) #b11111)
         (logand word #b11111)))
 
+(defun ez-make-zstring-word (zchar-triple)
+  (let ((c1 (elt zchar-triple 0))
+        (c2 (elt zchar-triple 1))
+        (c3 (elz zchar-triple 2)))
+    (logand )))
+
 (defun ez-get-zstring-chars-and-length (base-addr)
   (let ((addr base-addr)
         (chars nil)
@@ -287,31 +321,113 @@
          (chars (cdr word-count-and-chars))
          (cur 0)
          (lock 0)
-         (abbrev-char nil)
          (s ""))
-    (dolist (char chars)
-      (cond
-       (abbrev-char
-        (let ((abbrev-addr
-               (* 2 (ez-mem-ref-word (+ ez-abbrevtab-addr
-                                        (* 2 (+ (* (- abbrev-char 1) 32) char)))))))
-          (setq s (concat s (cdr (ez-get-zstring-and-length abbrev-addr)))))
-        (setq abbrev-char nil))
-       ((memq char '(1 2 3)) ;Abbreviation
-        (setq abbrev-char char))
-       ((= char 4)
-        (setq cur (mod (+ cur 1) 3)))
-       ((= char 5)
-        (setq cur (mod (+ 3 (- cur 1)) 3)))
-       (t 
-        (setq s (concat s (substring (elt ez-zstring-alphabets cur)
-                                     char (+ char 1))))
-        (setq cur lock))))
+    (while (> (length chars) 0)
+      (let ((char (pop chars)))
+        (cond
+         ((memq char '(1 2 3)) ;Abbreviation
+          (let* ((abbrev-char char)
+                 (abbrev-addr
+                  (* 2 (ez-mem-ref-word (+ ez-abbrevtab-addr
+                                           (* 2 (+ (* (- abbrev-char 1) 32) (pop chars))))))))
+            (setq s (concat s (cdr (ez-get-zstring-and-length abbrev-addr))))))
+         ((= char 4)
+          (setq cur (mod (+ cur 1) 3)))
+         ((= char 5)
+          (setq cur (mod (+ 3 (- cur 1)) 3)))
+         ((and (= cur 2) (= char 6))
+          (setq s (concat s (char-to-string (+ (lsh (pop chars) 5) (pop chars)))))
+          (setq cur lock))
+         (t 
+          (setq s (concat s (substring (elt ez-zstring-alphabets cur)
+                                       char (+ char 1))))
+          (setq cur lock)))))
     (cons word-count s)))
 
 (defun ez-get-zstring (base-addr)
   (cdr (ez-get-zstring-and-length base-addr)))
 
+(defun ez-encode (string)
+  "Encodes a string as a 2-word 5-padded Z-string.
+Used for matching input with dictionary entries when tokenizing.
+Returns a length-2 list of words for comparison with a dictionary entry."
+  (let ((chars
+         (mapcan
+          (lambda (c)
+            (cond
+             ((seq-contains-p (elt ez-zstring-alphabets 0) c)
+              (list (seq-position (elt ez-zstring-alphabets 0) c)))
+             ((seq-contains-p (elt ez-zstring-alphabets 1) c)
+              (list 4 (seq-position (elt ez-zstring-alphabets 1) c)))
+             ((seq-contains-p (elt ez-zstring-alphabets 2) c)
+              (list 5 (seq-position (elt ez-zstring-alphabets 2) c)))
+             (t
+              (list 5 6 (lsh c -5) (logand c #b11111)))))
+          string)))
+    (let* ((zstring-chars
+            (if (< (length chars) 6)
+                (append chars (make-list (- 6 (length chars)) 5))
+              (take 6 chars)))
+           (c1 (elt zstring-chars 0))
+           (c2 (elt zstring-chars 1))
+           (c3 (elt zstring-chars 2))
+           (c4 (elt zstring-chars 3))
+           (c5 (elt zstring-chars 4))
+           (c6 (elt zstring-chars 5)))
+      (list
+       (logior (lsh c1 10)
+               (lsh c2 5)
+               c3)
+       (logior (lsh 1 15)
+               (lsh c4 10)
+               (lsh c5 5)
+               c6)))))
+
+;; Dictionary
+
+(defun ez-parse-dictionary-header ()
+  (let* ((nseps (ez-mem-ref-byte ez-dict-base))
+         (separators
+          (mapcar (lambda (i) (ez-mem-ref-byte (+ ez-dict-base i)))
+                  (number-sequence 1 nseps)))
+         (bytes-per-entry (ez-mem-ref-byte (+ ez-dict-base 1 nseps)))
+         (nentries (ez-mem-ref-word (+ ez-dict-base 2 nseps)))
+         (entries-base (+ ez-dict-base nseps 4))
+         (entries nil))
+    ;; (dotimes (i nentries)
+    ;;   (let ((this-base (+ entries-base (* bytes-per-entry i))))
+    ;;     (setq entries (cons (cons (ez-get-zstring this-base)
+    ;;                               this-base)
+    ;;                         entries))))
+    ;; (setq ez-dict-entries (reverse entries))
+    (setq ez-dict-separators separators)))
+
+(defun ez-is-separator (char)
+  (let* ((nseps (ez-mem-ref-byte ez-dict-base)))
+    (while (and (> nseps 0)
+                (not (= (ez-mem-ref-byte (+ ez-dict-base nseps))
+                        char)))
+      (setq nseps (- nseps 1)))
+    (> nseps 0)))
+
+(defun ez-lookup-dictionary (text)
+  (let* ((encoded-text (ez-encode text))
+         (nseps (ez-mem-ref-byte ez-dict-base))
+         (bytes-per-entry (ez-mem-ref-byte (+ ez-dict-base 1 nseps)))
+         (nentries (ez-mem-ref-word (+ ez-dict-base 2 nseps)))
+         (entries-seen 0)
+         (this-entry (+ ez-dict-base nseps 4)))
+
+    (while (and (< entries-seen nentries)
+                (not (equal
+                      (ez-mem-ref-words this-entry 2)
+                      encoded-text)))
+      (setq entries-seen (+ entries-seen 1))
+      (setq this-entry (+ this-entry bytes-per-entry)))
+
+    (if (< entries-seen nentries)
+        this-entry
+      0)))
 
 ;; Call stack
 
@@ -334,25 +450,25 @@
 
 (defun ez-routine-stack-push (val)
   (let ((frame (car ez-call-stack)))
-    (message "\tPushed %x to stack" val)
+    (ez-debug-message "\tPushed %x to stack" val)
     (setf (elt frame 1) (cons val (elt frame 1)))))
 
 (defun ez-routine-stack-pop ()
   (let* ((frame (car ez-call-stack))
          (rs-head (car (elt frame 1))))
     (setf (elt frame 1) (cdr (elt frame 1)))
-    (message "\tPopped %x from stack" rs-head)
+    (ez-debug-message "\tPopped %x from stack" rs-head)
     rs-head))
 
 (defun ez-get-local-var (lvar)
   (let* ((frame (car ez-call-stack))
          (val (aref (elt frame 2) (- lvar 1))))
-    (message "\tRetrieved value %x from local variable %x" val lvar)
+    (ez-debug-message "\tRetrieved value %x from local variable %x" val lvar)
     val))
 
 (defun ez-set-local-var (lvar val)
   (let ((frame (car ez-call-stack)))
-    (message "\tSet local variable %x to %x" lvar val)
+    (ez-debug-message "\tSet local variable %x to %x" lvar val)
     (aset (elt frame 2) (- lvar 1) val)))
 
 (defun ez-get-pc ()
@@ -463,7 +579,7 @@
         (error "Unsupported op PC:%x Optype:%s Opcode:%x Operands:%s Operand-types:%s"
                instr-pc optype opcode (ez-list-to-string-hex operands) operand-types))
       (let ((mnemonic (elt table-row 1)))
-        (message "PC:%x Optype:%s Opcode:%x Mnemonic:%s Operands:%s Operand-types:%s"
+        (ez-debug-message "PC:%x Optype:%s Opcode:%x Mnemonic:%s Operands:%s Operand-types:%s"
                  instr-pc optype opcode mnemonic
                  (ez-list-to-string-hex operands) operand-types))
       (funcall (elt table-row 2) operands operand-types))))
@@ -535,6 +651,7 @@
     ((1op #x05) inc ez-op-inc)
     ((1op #x06) dec ez-op-dec)
     ((1op #x0B) ret ez-op-ret)
+    ((0op #x08) ret_pulled ez-op-ret-pulled)
     ((1op #x0C) jump ez-op-jump)
     ((2op #x05) inc_jg ez-op-inc-jg)
     ((2op #x04) dec_jg ez-op-dec-jg)
@@ -546,7 +663,9 @@
     ((2op #x10) loadb ez-op-loadb)
     ((2op #x01) je ez-op-je)
     ((2op #x02) jl ez-op-jl)
+    ((2op #x03) jg ez-op-jg)
     ((2op #x06) jin ez-op-jin)
+    ((2op #x07) test ez-op-test)
     ((2op #x08) or ez-op-or)
     ((2op #x09) and ez-op-and)
     ((2op #x14) add ez-op-add)
@@ -569,145 +688,158 @@
     ((0op #x0B) new_line ez-op-new-line)
     ((var #x06) print_num ez-op-print-num)
     ((var #x05) print_char ez-op-print-char)
-    ((1op #x0A) print_obj ez-op-print-obj)))
+    ((1op #x0A) print_obj ez-op-print-obj)
+    ((var #x04) read ez-op-read)))
 
 (defun ez-op-ret (operands &optional operand-types)
   (let ((retval (car operands)))
-    (message "\tReturning value %x" retval)
+    (ez-debug-message "\tReturning value %x" retval)
     (ez-pop-call-stack-frame)
     (ez-set-var (ez-read-pc-byte-and-inc) retval))
-  t)
+  'run)
+
+(defun ez-op-ret-pulled (operands operand-types)
+  (let ((retval (ez-routine-stack-pop)))
+    (ez-debug-message "\tReturning value %x" retval)
+    (ez-op-ret (list retval)))
+  'run)
 
 (defun ez-op-rtrue (&optional operands operand-types)
   (ez-op-ret (list 1))
-  t)
+  'run)
 
 (defun ez-op-rfalse (&optional operands operand-types)
   (ez-op-ret (list 0))
-  t)
+  'run)
 
 (defun ez-op-jz (operands operand-types)
   (ez-do-branch (= (car operands) 0))
-  t)
+  'run)
 
 (defun ez-op-je (operands operand-types)
   (ez-do-branch (memq (car operands) (cdr operands)))
-  t)
+  'run)
 
 (defun ez-op-jg (operands operand-types)
   (let ((s1 (ez-decode-signed-operand (car operands) (car operand-types)))
         (s2 (ez-decode-signed-operand (cadr operands) (cadr operand-types))))
     (ez-do-branch (> s1 s2)))
-  t)
+  'run)
 
 (defun ez-op-jl (operands operand-types)
   (let ((s1 (ez-decode-signed-operand (car operands) (car operand-types)))
         (s2 (ez-decode-signed-operand (cadr operands) (cadr operand-types))))
     (ez-do-branch (< s1 s2)))
-  t)
+  'run)
 
 (defun ez-op-inc-jg (operands operand-types)
   (let ((var (car operands)))
     (ez-op-inc (list var))
     (ez-op-jg (cons (ez-get-var var) (cdr operands)) (cons 'w (cdr operand-types))))
-  t)
+  'run)
 
 (defun ez-op-dec-jl (operands operand-types)
   (let ((var (car operands)))
     (ez-op-dec (list var))
     (ez-op-jl (cons (ez-get-var var) (cdr operands)) (cons 'w (cdr operand-types))))
-  t)
+  'run)
 
 (defun ez-op-jin (operands operand-types)
   (let ((obj (car operands))
         (n (cadr operands)))
     (ez-do-branch (or (= n 0)
                       (= n (ez-get-obj-parent obj)))))
-  t)
+  'run)
+
+(defun ez-op-test (operands operand-types)
+  (let ((a (car operands))
+        (b (cadr operands)))
+    (ez-do-branch (= (logand a b) b)))
+  'run)
 
 (defun ez-op-jump (operands operand-types)
   (let ((offset (if (eq (car operand-types) 'b)
                     (ez-decode-signed-byte (car operands))
                   (ez-decode-signed-word (car operands)))))
     (ez-set-pc (+ (ez-get-pc) offset -2)))
-  t)
+  'run)
 
 (defun ez-op-inc (operands &optional operand-types)
   (let ((var (car operands)))
     (ez-set-var var (mod (+ 1 (ez-get-var var)) #x10000)))
-  t)
+  'run)
 
 (defun ez-op-dec (operands &optional operand-types)
   (let ((var (car operands)))
     (ez-set-var var (mod (+ (ez-get-var var) 1) #x10000)))
-  t)
+  'run)
 
 (defun ez-op-store (operands operand-types)
   (let ((var (car operands))
         (a (cadr operands)))
     (ez-set-var var a))
-  t)
+  'run)
 
 (defun ez-op-load (operands operand-types)
   (let ((var (car operands)))
     (ez-set-var (ez-read-pc-byte-and-inc) (ez-get-var var)))
-  t)
+  'run)
 
 (defun ez-op-storew (operands operand-types)
   (let ((baddr (car operands))
         (n (cadr operands))
         (a (caddr operands)))
     (ez-mem-set-word (+ baddr (* 2 n)) a))
-  t)
+  'run)
 
 (defun ez-op-loadw (operands operand-types)
   (let ((baddr (car operands))
         (n (cadr operands)))
     (ez-set-var (ez-read-pc-byte-and-inc) (ez-mem-ref-word (+ baddr (* 2 n)))))
-  t)
+  'run)
 
 (defun ez-op-storeb (operands operand-types)
   (let ((baddr (car operands))
         (n (cadr operands))
         (a (caddr operands)))
     (ez-mem-set-byte (+ baddr n) a))
-  t)
+  'run)
 
 (defun ez-op-loadb (operands operand-types)
   (let ((baddr (car operands))
         (n (cadr operands)))
     (ez-set-var (ez-read-pc-byte-and-inc) (ez-mem-ref-byte (+ baddr n))))
-  t)
+  'run)
 
 (defun ez-op-and (operands operand-types)
   (let ((a (car operands))
         (b (cadr operands)))
     (ez-set-var (ez-read-pc-byte-and-inc) (logand a b)))
-  t)
+  'run)
 
 (defun ez-op-or (operands operand-types)
   (let ((a (car operands))
         (b (cadr operands)))
     (ez-set-var (ez-read-pc-byte-and-inc) (logior a b)))
-  t)
+  'run)
 
 (defun ez-op-add (operands operand-types)
   (let ((a (car operands))
         (b (cadr operands)))
     (ez-set-var (ez-read-pc-byte-and-inc) (mod (+ a b) #x10000)))
-  t)
+  'run)
 
 (defun ez-op-sub (operands operand-types)
   (let ((a (car operands))
         (b (cadr operands)))
     (ez-set-var (ez-read-pc-byte-and-inc) (mod (+ (- a b) #x10000) #x10000)))
-  t)
+  'run)
 
 (defun ez-op-mul (a b)
   (let ((a (car operands))
         (b (cadr operands)))
     (ez-set-var (ez-read-pc-byte-and-inc) (mod (* a b) #x10000)))
-  t)
+  'run)
 
 (defun ez-op-div (a b)
   (error "Not implemented"))
@@ -729,67 +861,67 @@
         (if (< i n)
             (ez-set-local-var (+ i 1) (elt call-operands i))
           (ez-set-local-var (+ i 1) (ez-mem-ref-word (+ r 1 (* 2 i))))))))
-  t)
+  'run)
 
 (defun ez-op-test-attr (operands operand-types)
   (let ((obj (car operands))
         (attr (cadr operands)))
     (ez-do-branch (= 1 (ez-get-obj-attr obj attr)))
-    t))
+    'run))
 
 (defun ez-op-set-attr (operands operand-types)
   (let ((obj (car operands))
         (attr (cadr operands)))
     (ez-set-obj-attr obj attr 1))
-  t)
+  'run)
 
 (defun ez-op-clear-attr (operands operand-types)
   (let ((obj (car operands))
         (attr (cadr operands)))
     (ez-set-obj-attr obj attr 0))
-  t)
+  'run)
 
 (defun ez-op-get-sibling (operands operand-types)
   (let ((sib (ez-get-obj-sibling (car operands))))
     (ez-set-var (ez-read-pc-byte-and-inc) sib)
     (ez-do-branch (> sib 0)))
-  t)
+  'run)
 
 (defun ez-op-get-child (operands operand-types)
   (let ((child (ez-get-obj-child (car operands))))
     (ez-set-var (ez-read-pc-byte-and-inc) child)
     (ez-do-branch (> child 0)))
-  t)
+  'run)
 
 (defun ez-op-get-parent (operands operand-types)
   (let ((parent (ez-get-obj-parent (car operands))))
     (ez-set-var (ez-read-pc-byte-and-inc) parent))
-  t)
+  'run)
 
 (defun ez-op-remove-obj (operands operand-types)
   (let ((obj (car operands)))
     (ez-remove-obj obj))
-  t)
+  'run)
 
 (defun ez-op-insert-obj (operands operand-types)
   (let ((obj1 (car operands))
         (obj2 (cadr operands)))
     (ez-insert-obj obj1 obj2))
-  t)
+  'run)
 
 (defun ez-op-put-prop (operands operand-types)
   (let* ((obj (car operands))
          (prop (cadr operands))
          (a (caddr operands)))
     (ez-set-obj-prop obj prop a))
-  t)
+  'run)
 
 (defun ez-op-get-prop (operands operand-types)
   (let* ((obj (car operands))
          (prop (cadr operands)))
     (ez-set-var (ez-read-pc-byte-and-inc)
                 (ez-get-obj-prop obj prop)))
-  t)
+  'run)
 
 (defun ez-op-print (operands operand-types)
   (let* ((word-count-and-string (ez-get-zstring-and-length (ez-get-pc)))
@@ -797,88 +929,164 @@
          (string (cdr word-count-and-string)))
     (ez-print string)
     (ez-increment-pc (* 2 word-count)))
-  t)
+  'run)
 
 (defun ez-op-new-line (operands operand-types)
   (ez-print "\n")
-  t)
+  'run)
 
 (defun ez-op-print-num (operands operand-types)
   (let ((s (ez-decode-signed-operand (car operands) (car operand-types))))
     (ez-print (number-to-string s)))
-  t)
+  'run)
 
 (defun ez-op-print-char (operands operand-types)
   (let ((c (car operands)))
     (ez-print (string c)))
-  t)
+  'run)
 
 (defun ez-op-print-obj (operands operand-types)
   (let ((obj (car operands)))
     (ez-print (ez-get-obj-name obj)))
-  t)
+  'run)
+
+(defvar ez--next-read-args nil)
+(defun ez-op-read (operands operand-types)
+  (let ((baddr1 (car operands))
+        (baddr2 (cadr operands)))
+    (setq ez--next-read-args (list baddr1 baddr2)))
+  'wait-for-input)
+
+(defun ez-op-read2 (input-string)
+  (let* ((baddr1 (car ez--next-read-args))
+         (baddr2 (cadr ez--next-read-args)))
+
+    (dotimes (i (length input-string))
+      (let ((char (elt input-string i)))
+        (ez-mem-set-byte (+ baddr1 1 i) char)))
+    (ez-mem-set-byte (+ baddr1 1 (length input-string)) 0)
+
+    (ez--tokenize baddr1 baddr2))
+  'run)
+
+(defun ez--tokenize (tb-baddr pb-baddr)
+
+  (let ((unfinished t)
+        (token-start 0)
+        (token-end 0)
+        (token-count 0))
+
+    (while unfinished
+      (let ((next-char (ez-mem-ref-byte (+ tb-baddr 1 token-end))))
+        (cond
+         ((eq next-char ?\s)
+          ;; Add token
+          (setq token-end (- token-end 1))
+          (let* ((text (ez-mem-ref-string (+ tb-baddr 1 token-start)
+                                         (+ tb-baddr 1 token-end)))
+                 (dict-entry (ez-lookup-dictionary text)))
+            (setq token-count (+ token-count 1))
+            (ez-mem-set-word (+ pb-baddr 2 (* token-count 4))
+                             dict-entry)
+            (ez-mem-set-bytes (+ pb-baddr 2 (* token-count 4) 2)
+                              (length text)
+                              token-start))
+          (setq token-start (+ token-end 1))
+          (setq token-end token-start))
+
+         ((ez-is-separator char)
+          ;; Add token and separator token
+          )
+         ((eq char 0)
+          (setq unfinished nil))
+         (setq token-end (+ token-end 1)))
+      ))))
 
 ;; Execution loop
 
-(defun ez-run (filename)
+(defun ez-load-and-run (filename)
   (ez-load-file filename)
   (ez-parse-header)
   (setq ez-call-stack (list (ez-make-call-stack-frame ez-start-pc)))
 
-  (while (ez-execute-instr)))
+  (ez-run))
 
+(defvar ez-machine-state nil
+  "Identifies the current executation state of the Z-machine.")
+
+(defun ez-run ()
+  (setq ez-machine-state 'run)
+  (while (eq ez-machine-state 'run)
+    (setq ez-machine-state (ez-execute-instr))))
 
 ;;; Buffer and I/O
 ;;
 
-(defun ez-render-prompt ()
-  (with-current-buffer "*ez*"
-    (let ((update-point (= ez-input-marker (point)))
-          (update-window-points (mapcar (lambda (w)
-                                          (list (= (window-point w) ez-input-marker)
-                                                w))
-                                        (get-buffer-window-list nil nil t))))
-      (save-excursion
-        (set-marker-insertion-type ez-prompt-marker nil)
-        (set-marker-insertion-type ez-input-marker t)
-        (let ((inhibit-read-only t))
-          (delete-region ez-prompt-marker ez-input-marker)
-          (goto-char ez-prompt-marker)
-          (insert
-           ">"
-           (propertize " " ; Need this to be separate to mark it as rear-nonsticky
-                       'read-only t
-                       'rear-nonsticky t)))
-        (set-marker-insertion-type ez-input-marker nil))
-      (goto-char ez-input-marker))))
-
-(defvar ez-prompt-marker nil
-  "Marker for prompt position in buffer.")
-
 (defvar ez-input-marker nil
-  "Marker for prompt position in buffer.")
+  "Marker for input position in buffer.")
 
 (defun ez-setup-buffer ()
   (with-current-buffer (get-buffer-create "*ez*")
+    (ez-mode)
     (let ((inhibit-read-only t))
-      (delete-region (point-min) (point-max)))
+      (erase-buffer))
     (setq-local scroll-conservatively 1)
-    (if (markerp ez-prompt-marker)
-        (set-marker ez-prompt-marker (point-max))
-      (setq ez-prompt-marker (point-max-marker)))
     (if (markerp ez-input-marker)
         (set-marker ez-input-marker (point-max))
       (setq ez-input-marker (point-max-marker)))
-    (goto-char (point-max))
-    (ez-render-prompt)))
+    (goto-char (point-max))))
 
 
 (defun ez-print (string)
   (with-current-buffer "*ez*"
     (save-excursion
-      (goto-char ez-prompt-marker)
+      (goto-char ez-input-marker)
       (insert-before-markers string))))
 
+(defun ez-enter ()
+  (interactive)
+  (if (not (eq ez-machine-state 'wait-for-input))
+      (error "Z-machine not ready for input."))
+  (let ((input-string
+         (downcase
+          (with-current-buffer "*ez*"
+            (buffer-substring ez-input-marker (point-max))))))
+    (delete-region ez-input-marker (point-max))
+    (ez-print (concat input-string "\n"))
+    (ez-debug-message "\tReceived string \"%s\"" input-string)
+    (ez-op-read2 input-string)
+    (ez-run)))
+
+;; Debugging info
+
+(defun ez-setup-debug-buffer ()
+  (with-current-buffer (get-buffer-create "*ez-debug-trace*")
+    (setq-local buffer-read-only t)
+    (let ((inhibit-read-only t))
+      (erase-buffer)
+      (insert "--- Trace Start ---\n\n"))))
+
+(defun ez-debug-message (&rest strings)
+  (with-current-buffer (get-buffer-create "*ez-debug-trace*")
+    (save-excursion
+      (goto-char (point-max))
+      (let ((inhibit-read-only t))
+        (insert (apply #'format-message strings) "\n")))))
+
+(defun ez-debug-memory ()
+  (interactive)
+  (with-current-buffer (get-buffer-create "*ez-debug-memory*")
+    (setq-local buffer-read-only t)
+    (let ((inhibit-read-only t)
+          (old-point (point)))
+      (if (eq major-mode 'hexl-mode)
+          (hexl-mode-exit))
+      (erase-buffer)
+      (insert ez-memory)
+      (setq-local buffer-undo-list nil)
+      (hexl-mode)
+      (goto-char old-point))))
+
 ;; Mode
 
 (defvar ez-mode-map
@@ -897,16 +1105,14 @@
   (if (get-buffer "*ez*")
       (switch-to-buffer "*ez*")
     (switch-to-buffer "*ez*")
-    (ez-mode)
     (ez-setup-buffer)
-    (ez-run zfile))
+    (ez-load-and-run zfile))
   "Started EZ.")
 
 (defun ez-debug ()
   (interactive)
-  (switch-to-buffer "*ez*")
-  (ez-mode)
   (ez-setup-buffer)
-  (ez-run "zork1.z3"))
+  (ez-setup-debug-buffer)
+  (ez-load-and-run "zork1.z3"))
 
 ;;; ez.el ends here