From e35cff6d299a07d9b34f303717083a9299a37e82 Mon Sep 17 00:00:00 2001
From: "Juan J. Martinez" <jjm@usebox.net>
Date: Mon, 28 Aug 2023 15:16:12 +0100
Subject: Initial import

---
 src/timer.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)
 create mode 100644 src/timer.c

(limited to 'src/timer.c')

diff --git a/src/timer.c b/src/timer.c
new file mode 100644
index 0000000..a55d0c0
--- /dev/null
+++ b/src/timer.c
@@ -0,0 +1,78 @@
+#include <stdint.h>
+#include <go32.h>
+#include <dpmi.h>
+#include <stddef.h>
+
+volatile uint32_t ubox_ticks = 0;
+volatile uint32_t clock = 0;
+volatile uint8_t clock_secs = 0;
+volatile uint8_t clock_enabled = 0;
+volatile uint8_t *clock_updated = NULL;
+volatile void (*user_fn)(void) = NULL;
+
+static _go32_dpmi_seginfo old_handler, new_handler;
+
+static void timer_handler()
+{
+    ubox_ticks++;
+
+    if (clock_enabled)
+    {
+        clock += 5494;
+        if (clock > 100000)
+        {
+            clock -= 100000;
+            if (clock_secs)
+            {
+                clock_secs--;
+                if (clock_updated)
+                    *clock_updated = 1;
+            }
+        }
+    }
+
+    if (user_fn)
+        user_fn();
+}
+
+void ubox_timer_init()
+{
+    _go32_dpmi_get_protected_mode_interrupt_vector(0x1c, &old_handler);
+    new_handler.pm_offset = (unsigned long)timer_handler;
+    new_handler.pm_selector = _go32_my_cs();
+    _go32_dpmi_chain_protected_mode_interrupt_vector(0x1c, &new_handler);
+}
+
+void ubox_timer_user_fn(void (*fn)(void))
+{
+    user_fn = fn;
+}
+
+void ubox_timer_free()
+{
+    _go32_dpmi_set_protected_mode_interrupt_vector(0x1c, &old_handler);
+}
+
+void ubox_timer_start(uint8_t secs, volatile uint8_t *updated)
+{
+    *updated = 0;
+    clock_updated = updated;
+    clock_secs = secs;
+    clock_enabled = 1;
+}
+
+uint8_t ubox_timer_value()
+{
+    *clock_updated = 0;
+    return clock_secs;
+}
+
+void ubox_timer_stop()
+{
+    clock_enabled = 0;
+}
+
+void ubox_timer_resume()
+{
+    clock_enabled = 1;
+}
-- 
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