From db0363462f42b05561853bd295fb4d39909a9f6c Mon Sep 17 00:00:00 2001
From: "Kartik K. Agaram" <vc@akkartik.com>
Date: Wed, 13 Oct 2021 23:14:20 -0700
Subject: [PATCH] primitive: read line from keyboard

Blocking.
---
 516read-line.mu | 20 ++++++++++++++++++++
 apps/rpn.mu     | 20 +-------------------
 2 files changed, 21 insertions(+), 19 deletions(-)
 create mode 100644 516read-line.mu

diff --git a/516read-line.mu b/516read-line.mu
new file mode 100644
index 00000000..1bb79c5a
--- /dev/null
+++ b/516read-line.mu
@@ -0,0 +1,20 @@
+# read line from keyboard into stream while also echoing to screen
+# abort on stream overflow
+fn read-line-from-keyboard keyboard: (addr keyboard), out: (addr stream byte), screen: (addr screen), fg: int, bg: int {
+  clear-stream out
+  {
+    draw-cursor screen, 0x20/space
+    var key/eax: byte <- read-key keyboard
+    compare key, 0xa/newline
+    break-if-=
+    compare key, 0
+    loop-if-=
+    var key2/eax: int <- copy key
+    append-byte out, key2
+    var c/eax: code-point <- copy key2
+    draw-code-point-at-cursor-over-full-screen screen, c, fg bg
+    loop
+  }
+  # clear cursor
+  draw-code-point-at-cursor-over-full-screen screen, 0x20/space, fg bg
+}
diff --git a/apps/rpn.mu b/apps/rpn.mu
index 4fd8ccb6..7d98d549 100644
--- a/apps/rpn.mu
+++ b/apps/rpn.mu
@@ -19,28 +19,10 @@ fn main screen: (addr screen), keyboard: (addr keyboard), data-disk: (addr disk)
   var in-storage: (stream byte 0x80)
   var in/esi: (addr stream byte) <- address in-storage
   var y/ecx: int <- copy 0
-  var space/edx: code-point <- copy 0x20
   # read-eval-print loop
   {
-    # print prompt
     var x/eax: int <- draw-text-rightward screen, "> ", 0/x, 0x80/xmax, y, 3/fg/cyan, 0/bg
-    # read line from keyboard
-    clear-stream in
-    {
-      draw-cursor screen, space
-      var key/eax: byte <- read-key keyboard
-      compare key, 0xa/newline
-      break-if-=
-      compare key, 0
-      loop-if-=
-      var key2/eax: int <- copy key
-      append-byte in, key2
-      var c/eax: code-point <- copy key2
-      draw-code-point-at-cursor-over-full-screen screen, c, 0xf/fg, 0/bg
-      loop
-    }
-    # clear cursor
-    draw-code-point-at-cursor-over-full-screen screen, space, 3/fg/never-used, 0/bg
+    read-line-from-keyboard keyboard, in, screen, 0xf/fg 0/bg
     # parse and eval
     var out/eax: int <- simplify in
     # print