From a1de326ac5d89cbf9555c9a0a9a662af35c6dcf7 Mon Sep 17 00:00:00 2001
From: "Juan J. Martinez" <jjm@usebox.net>
Date: Thu, 15 Jun 2023 22:58:30 +0100
Subject: Implement a countdown clock in the timer

Updated the HUD to show the time.
---
 src/game.c  | 13 ++++++++++++-
 src/game.h  |  5 +++--
 src/keyb.h  |  2 +-
 src/main.c  | 10 +++++++++-
 src/timer.c | 45 ++++++++++++++++++++++++++++++++++++++++-----
 src/timer.h |  7 +++++--
 6 files changed, 70 insertions(+), 12 deletions(-)

diff --git a/src/game.c b/src/game.c
index 70c3235..b49e859 100644
--- a/src/game.c
+++ b/src/game.c
@@ -12,12 +12,14 @@
 static uint32_t hiscore = 15000;
 
 static uint8_t hud;
+static volatile uint8_t clock_updated;
 
 /* game variables */
 static uint8_t lives;
 static uint32_t score;
 static uint8_t stage;
 static uint8_t gold;
+static uint8_t time;
 
 void hud_render()
 {
@@ -49,7 +51,7 @@ void hud_render()
 
     if (hud & HUD_TIME)
     {
-        sprintf(b, "%02d", 0);
+        sprintf(b, "%02d", time);
         put_text(172, 4, b);
     }
 
@@ -68,14 +70,23 @@ void run_game()
     score = 0;
     stage = 0;
     gold = 30;
+    time = GAME_TIME_MAX;
 
     hud = HUD_ALL;
 
     map_init(binary_stage_start);
     map_render();
 
+    timer_start(GAME_TIME_MAX, &clock_updated);
+
     while (!keys[KEY_ESC])
     {
+        if (clock_updated)
+        {
+            time = timer_value();
+            hud |= HUD_TIME;
+        }
+
         if (hud)
             hud_render();
 
diff --git a/src/game.h b/src/game.h
index e8c270e..ff90121 100644
--- a/src/game.h
+++ b/src/game.h
@@ -1,8 +1,9 @@
 #ifndef _GAME_H
 #define _GAME_H
 
-#define GAME_LIVES_START 3
-#define GAME_LIVES_MAX 9
+#define GAME_LIVES_START    3
+#define GAME_LIVES_MAX      9
+#define GAME_TIME_MAX       60
 
 #define HUD_CLEAN   0
 #define HUD_LIVES   1
diff --git a/src/keyb.h b/src/keyb.h
index 5e47502..3a9e10c 100644
--- a/src/keyb.h
+++ b/src/keyb.h
@@ -9,7 +9,7 @@ void keyb_free();
 #define KEY_ESC 1
 #define KEY_TAB 15
 #define KEY_ENTER 28
-#define KEY_SPACEBAR 57
+#define KEY_SPACE 57
 
 #define KEY_A 30
 #define KEY_S 31
diff --git a/src/main.c b/src/main.c
index 306f5f1..0711cf9 100644
--- a/src/main.c
+++ b/src/main.c
@@ -4,6 +4,7 @@
 #include <stdio.h>
 #include <crt0.h>
 
+#include "timer.h"
 #include "keyb.h"
 #include "vga.h"
 #include "data.h"
@@ -12,10 +13,17 @@
 /* disable paging because our int handlers are written in C */
 int _crt0_startup_flags = _CRT0_FLAG_LOCK_MEMORY;
 
+void free_all()
+{
+    timer_free();
+    keyb_free();
+}
+
 int main(int argc, char *argv[])
 {
+    timer_init();
     keyb_init();
-    atexit(keyb_free);
+    atexit(free_all);
 
     /* set VGA 320x200, 256 col */
     if (!set_mode(0x13))
diff --git a/src/timer.c b/src/timer.c
index d7810b6..ae76037 100644
--- a/src/timer.c
+++ b/src/timer.c
@@ -4,14 +4,31 @@
 #include <dpmi.h>
 
 volatile uint32_t ticks = 0;
-volatile static uint32_t ticks_to = 0;
+volatile uint32_t clock = 0;
+volatile uint8_t clock_secs = 0;
+volatile uint8_t clock_enabled = 0;
+volatile uint8_t *clock_updated = NULL;
 
 static _go32_dpmi_seginfo old_handler, new_handler;
 
 static void timer_handler()
 {
     ticks++;
-    ticks_to++;
+
+    if (clock_enabled)
+    {
+        clock += 5494;
+        if (clock > 100000)
+        {
+            clock -= 100000;
+            if (clock_secs)
+            {
+                clock_secs--;
+                if (clock_updated)
+                    *clock_updated = 1;
+            }
+        }
+    }
 }
 
 void timer_init()
@@ -28,8 +45,26 @@ void timer_free()
         fprintf(stderr, "Failed to free the timer :(\n");
 }
 
-void timer_wait(uint8_t t)
+void timer_start(uint8_t secs, uint8_t *updated)
+{
+    *updated = 0;
+    clock_updated = updated;
+    clock_secs = secs;
+    clock_enabled = 1;
+}
+
+uint8_t timer_value()
+{
+    *clock_updated = 0;
+    return clock_secs;
+}
+
+void timer_stop()
+{
+    clock_enabled = 0;
+}
+
+void timer_resume()
 {
-    while (ticks_to < t);
-    ticks_to = 0;
+    clock_enabled = 1;
 }
diff --git a/src/timer.h b/src/timer.h
index 8ae7e60..3f66be5 100644
--- a/src/timer.h
+++ b/src/timer.h
@@ -7,7 +7,10 @@ extern volatile uint32_t ticks;
 void timer_init();
 void timer_free();
 
-/* each t is 54.9254 ms */
-void timer_wait(uint8_t t);
+/* countdown clock */
+void timer_start(uint8_t secs, uint8_t *updated);
+uint8_t timer_value();
+void timer_stop();
+void timer_resume();
 
 #endif /* _TIMER_H */
-- 
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