pulled in and adapted the dos code from eradicate

[retrobench] / src / dos / timer.c

diff --git a/src/dos/timer.c b/src/dos/timer.c
new file mode 100644 (file)
index 0000000..0dc4447
--- /dev/null
+++ b/src/dos/timer.c
@@ -0,0 +1,175 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+#include <conio.h>
+#include <dos.h>
+
+#ifdef __WATCOMC__
+#include <i86.h>
+#endif
+
+#ifdef __DJGPP__
+#include <dpmi.h>
+#include <go32.h>
+#include <pc.h>
+#endif
+
+#include "pit8254.h"
+#include "util.h"
+
+#define PIT_TIMER_INTR 8
+#define DOS_TIMER_INTR 0x1c
+
+/* macro to divide and round to the nearest integer */
+#define DIV_ROUND(a, b) \
+       ((a) / (b) + ((a) % (b)) / ((b) / 2))
+
+static void set_timer_reload(int reload_val);
+static void cleanup(void);
+
+#ifdef __WATCOMC__
+#define INTERRUPT      __interrupt __far
+
+static void INTERRUPT dos_timer_intr();
+
+static void (INTERRUPT *prev_timer_intr)();
+#endif
+
+#ifdef __DJGPP__
+#define INTERRUPT
+
+static _go32_dpmi_seginfo intr, prev_intr;
+
+#define outp(p, v)     outportb(p, v)
+#endif
+
+static void INTERRUPT timer_irq();
+
+static volatile unsigned long ticks;
+static unsigned long tick_interval, ticks_per_dos_intr;
+static int inum;
+
+void init_timer(int res_hz)
+{
+       _disable();
+
+       if(res_hz > 0) {
+               int reload_val = DIV_ROUND(OSC_FREQ_HZ, res_hz);
+               set_timer_reload(reload_val);
+
+               tick_interval = DIV_ROUND(1000, res_hz);
+               ticks_per_dos_intr = DIV_ROUND(65535L, reload_val);
+
+               inum = PIT_TIMER_INTR;
+#ifdef __WATCOMC__
+               prev_timer_intr = _dos_getvect(inum);
+               _dos_setvect(inum, timer_irq);
+#endif
+#ifdef __DJGPP__
+               _go32_dpmi_get_protected_mode_interrupt_vector(inum, &prev_intr);
+               intr.pm_offset = (intptr_t)timer_irq;
+               intr.pm_selector = _go32_my_cs();
+               _go32_dpmi_allocate_iret_wrapper(&intr);
+               _go32_dpmi_set_protected_mode_interrupt_vector(inum, &intr);
+#endif
+       } else {
+               tick_interval = 55;
+
+               inum = DOS_TIMER_INTR;
+#ifdef __WATCOMC__
+               prev_timer_intr = _dos_getvect(inum);
+               _dos_setvect(inum, dos_timer_intr);
+#endif
+#ifdef __DJGPP__
+               assert(0);
+#endif
+       }
+       _enable();
+
+       atexit(cleanup);
+}
+
+static void cleanup(void)
+{
+       if(!inum) {
+               return; /* init hasn't ran, there's nothing to cleanup */
+       }
+
+       _disable();
+       if(inum == PIT_TIMER_INTR) {
+               /* restore the original timer frequency */
+               set_timer_reload(65535);
+       }
+
+       /* restore the original interrupt handler */
+#ifdef __WATCOMC__
+       _dos_setvect(inum, prev_timer_intr);
+#endif
+#ifdef __DJGPP__
+       _go32_dpmi_set_protected_mode_interrupt_vector(inum, &prev_intr);
+       _go32_dpmi_free_iret_wrapper(&intr);
+#endif
+
+       _enable();
+}
+
+void reset_timer(void)
+{
+       ticks = 0;
+}
+
+unsigned long get_msec(void)
+{
+       return ticks * tick_interval;
+}
+
+void sleep_msec(unsigned long msec)
+{
+       unsigned long wakeup_time = ticks + msec / tick_interval;
+       while(ticks < wakeup_time) {
+#ifdef USE_HLT
+               halt();
+#endif
+       }
+}
+
+static void set_timer_reload(int reload_val)
+{
+       outp(PORT_CMD, CMD_CHAN0 | CMD_ACCESS_BOTH | CMD_OP_SQWAVE);
+       outp(PORT_DATA0, reload_val & 0xff);
+       outp(PORT_DATA0, (reload_val >> 8) & 0xff);
+}
+
+#ifdef __WATCOMC__
+static void INTERRUPT dos_timer_intr()
+{
+       ticks++;
+       _chain_intr(prev_timer_intr);   /* DOES NOT RETURN */
+}
+#endif
+
+/* first PIC command port */
+#define PIC1_CMD       0x20
+/* end of interrupt control word */
+#define OCW2_EOI       (1 << 5)
+
+static void INTERRUPT timer_irq()
+{
+       static unsigned long dos_ticks;
+
+       ticks++;
+
+#ifdef __WATCOMC__
+       if(++dos_ticks >= ticks_per_dos_intr) {
+               /* I suppose the dos irq handler does the EOI so I shouldn't
+                * do it if I am to call the previous function
+                */
+               dos_ticks = 0;
+               _chain_intr(prev_timer_intr);   /* XXX DOES NOT RETURN */
+               return; /* just for clarity */
+       }
+#endif
+
+       /* send EOI to the PIC */
+       outp(PIC1_CMD, OCW2_EOI);
+}