From e6a14422966604c0f951ff0f9d1c481251fca2d9 Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Sun, 3 Jan 2021 02:45:25 +0100
Subject: [PATCH] sys.wait() no longer resets the jiffyclock to zero

---
 compiler/res/prog8lib/c64/syslib.p8  | 10 +++++++---
 compiler/res/prog8lib/cx16/syslib.p8 |  9 ++++++---
 docs/source/todo.rst                 |  1 -
 examples/test.p8                     |  8 +++-----
 4 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/compiler/res/prog8lib/c64/syslib.p8 b/compiler/res/prog8lib/c64/syslib.p8
index 3648c0583..8bc9b4bf7 100644
--- a/compiler/res/prog8lib/c64/syslib.p8
+++ b/compiler/res/prog8lib/c64/syslib.p8
@@ -485,11 +485,15 @@ sys {
     }
 
     sub wait(uword jiffies) {
-        c64.SETTIM(0,0,0)           ; TODO do the wait without resetting the jiffy clock
-        while c64.RDTIM16() < jiffies {
-            ; wait till the time catches up
+        ; --- wait approximately the given number of jiffies (1/60th seconds)
+        repeat jiffies {
+            ubyte jiff = lsb(c64.RDTIM16())
+            while jiff==lsb(c64.RDTIM16()) {
+                ; wait until 1 jiffy has passed
+            }
         }
     }
+
 }
 
 cx16 {
diff --git a/compiler/res/prog8lib/cx16/syslib.p8 b/compiler/res/prog8lib/cx16/syslib.p8
index 1ab32856c..aa8dfed87 100644
--- a/compiler/res/prog8lib/cx16/syslib.p8
+++ b/compiler/res/prog8lib/cx16/syslib.p8
@@ -474,9 +474,12 @@ sys {
     }
 
     sub wait(uword jiffies) {
-        c64.SETTIM(0,0,0)           ; TODO do the wait without resetting the jiffy clock
-        while c64.RDTIM16() < jiffies {
-            ; wait till the time catches up
+        ; --- wait approximately the given number of jiffies (1/60th seconds)
+        repeat jiffies {
+            ubyte jiff = lsb(c64.RDTIM16())
+            while jiff==lsb(c64.RDTIM16()) {
+                ; wait until 1 jiffy has passed
+            }
         }
     }
 
diff --git a/docs/source/todo.rst b/docs/source/todo.rst
index d5513513a..94dbd5acb 100644
--- a/docs/source/todo.rst
+++ b/docs/source/todo.rst
@@ -3,7 +3,6 @@ TODO
 ====
 
 - move all str* builtin functions to a str library module
-- make the syslib.wait() functions not reset the jiffy clock to 0
 - detect variables that are written but never read - mark those as unused too and remove them, such as uword unused = memory("unused222", 20) - also remove the memory slab allocation
 - hoist all variable declarations up to the subroutine scope *before* even the constant folding takes place (to avoid undefined symbol errors when referring to a variable from another nested scope in the subroutine)
 - make it possible to use cpu opcodes such as 'nop' as variable names by prefixing all asm vars with something such as '_'
diff --git a/examples/test.p8 b/examples/test.p8
index e9fb7a997..e104cf37e 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -1,6 +1,6 @@
 %import test_stack
 %import textio
-%zeropage full
+%zeropage basicsafe
 %option no_sysinit
 
 main {
@@ -8,13 +8,11 @@ main {
     sub start () {
         uword current_time
 
-        repeat 5 {
+        repeat 6 {
             current_time = c64.RDTIM16()
             txt.print_uw(current_time)
             txt.chrout('\n')
-            repeat 60000 {
-                current_time++
-            }
+            sys.wait(30)
         }