From 09dca7b4aabbb22b6febbc5ec1f328abc2fc6a86 Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Tue, 21 Jan 2025 07:33:39 -0800
Subject: get-csv: simplify implementation by CR-LF folding.

* stdlib/csv.tl (get-csv): Pre-process the input by a small
state machine that maps CR-LF sequences to LF. Then
we don't have to recognize #\return anywhere in the state
machine and can delete the cr and qcr states, as well
as all the code recognizing #\return and branching to those
states.
---
 stdlib/csv.tl | 37 +++++++------------------------------
 1 file changed, 7 insertions(+), 30 deletions(-)

diff --git a/stdlib/csv.tl b/stdlib/csv.tl
index 9b03f3ce..c56d2520 100644
--- a/stdlib/csv.tl
+++ b/stdlib/csv.tl
@@ -28,16 +28,21 @@
 (defun get-csv (: (stream *stdin*))
   (if (stringp stream)
     (upd stream make-string-input-stream))
-  (enumlet (rfield qfield cr qcr quot)
+  (enumlet (rfield qfield quot)
     (let ((record (vec))
           (field (str 0))
           (state rfield)
           (done nil))
       (while (not done)
         (let ((ch (get-char stream)))
+          (when (eq ch #\return)
+            (let ((ch2 (get-char stream)))
+              (if (eq ch2 #\newline)
+                (set ch ch2)
+                (if ch2
+                  (unget-char ch2 stream)))))
           (caseql* state
             (rfield (caseql* ch
-                      (#\return  (set state cr))
                       (#\newline (vec-push record field)
                                  (set done t))
                       (#\,       (vec-push record field)
@@ -52,36 +57,9 @@
                       (t         (string-extend field ch))))
             (qfield (caseql* ch
                       (#\"       (set state quot))
-                      (#\return  (set state qcr))
                       (nil       (vec-push record field)
                                  (set done t))
                       (t         (string-extend field ch))))
-            (cr     (caseql* ch
-                      (#\newline (vec-push record field)
-                                 (set done t))
-                      (#\return  (string-extend field ch))
-                      (#\,       (string-extend field #\return)
-                                 (vec-push record field)
-                                 (set field (str 0)
-                                      state rfield))
-                      (nil       (string-extend field #\return)
-                                 (vec-push record field)
-                                 (set done t))
-                      (t         (string-extend field #\return)
-                                 (string-extend field ch)
-                                 (set state rfield))))
-            (qcr    (caseql* ch
-                      (#\newline (string-extend field ch)
-                                 (set state qfield))
-                      (#\return  (string-extend field ch))
-                      (nil       (string-extend field #\return)
-                                 (vec-push record field)
-                                 (set done t))
-                      (#\"       (string-extend field #\return)
-                                 (set state quot))
-                      (t         (string-extend field #\return)
-                                 (string-extend field ch)
-                                 (set state qfield))))
             (quot   (caseql* ch
                       (#\,       (vec-push record field)
                                  (set field (str 0)
@@ -90,7 +68,6 @@
                                  (set state qfield))
                       (#\newline (vec-push record field)
                                  (set done t))
-                      (#\return  (set state cr))
                       (nil       (vec-push record field)
                                  (set done t))
                       (t         (string-extend field ch)
-- 
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