Add LPT device emulation framework.

Move long-broken DAC and Sound Source emulation to new framework.
Add stereo DAC emulation.

src/lpt_dac.c

@@ -0,0 +1,115 @@
+#include <stdlib.h>
+#include "ibm.h"
+#include "filters.h"
+#include "lpt.h"
+#include "lpt_dac.h"
+#include "sound.h"
+
+typedef struct lpt_dac_t
+{
+        uint8_t dac_val_l, dac_val_r;
+        
+        int is_stereo;
+        int channel;
+        
+        int16_t buffer[2][MAXSOUNDBUFLEN];
+        int pos;
+} lpt_dac_t;
+
+static void dac_update(lpt_dac_t *lpt_dac)
+{
+        for (; lpt_dac->pos < sound_pos_global; lpt_dac->pos++)
+        {
+                lpt_dac->buffer[0][lpt_dac->pos] = (int8_t)(lpt_dac->dac_val_l ^ 0x80) * 0x40;
+                lpt_dac->buffer[1][lpt_dac->pos] = (int8_t)(lpt_dac->dac_val_r ^ 0x80) * 0x40;
+        }
+}
+
+
+static void dac_write_data(uint8_t val, void *p)
+{
+        lpt_dac_t *lpt_dac = (lpt_dac_t *)p;
+
+        if (lpt_dac->is_stereo)
+        {
+                if (lpt_dac->channel)
+                        lpt_dac->dac_val_r = val;
+                else
+                        lpt_dac->dac_val_l = val;
+        }
+        else        
+                lpt_dac->dac_val_l = lpt_dac->dac_val_r = val;
+        dac_update(lpt_dac);
+}
+
+static void dac_write_ctrl(uint8_t val, void *p)
+{
+        lpt_dac_t *lpt_dac = (lpt_dac_t *)p;
+
+        if (lpt_dac->is_stereo)
+                lpt_dac->channel = val & 0x01;
+}
+
+static uint8_t dac_read_status(void *p)
+{
+        return 0;
+}
+
+
+static void dac_get_buffer(int32_t *buffer, int len, void *p)
+{
+        lpt_dac_t *lpt_dac = (lpt_dac_t *)p;
+        int c;
+        
+        dac_update(lpt_dac);
+        
+        for (c = 0; c < len; c++)
+        {
+                buffer[c*2]     += dac_iir(0, lpt_dac->buffer[0][c]);
+                buffer[c*2 + 1] += dac_iir(1, lpt_dac->buffer[1][c]);
+        }
+        lpt_dac->pos = 0;
+}
+
+static void *dac_init()
+{
+        lpt_dac_t *lpt_dac = malloc(sizeof(lpt_dac_t));
+        memset(lpt_dac, 0, sizeof(lpt_dac_t));
+
+        sound_add_handler(dac_get_buffer, lpt_dac);
+                
+        return lpt_dac;
+}
+static void *dac_stereo_init()
+{
+        lpt_dac_t *lpt_dac = dac_init();
+        
+        lpt_dac->is_stereo = 1;
+                
+        return lpt_dac;
+}
+static void dac_close(void *p)
+{
+        lpt_dac_t *lpt_dac = (lpt_dac_t *)p;
+        
+        free(lpt_dac);
+}
+
+lpt_device_t lpt_dac_device =
+{
+        "LPT DAC / Covox Speech Thing",
+        dac_init,
+        dac_close,
+        dac_write_data,
+        dac_write_ctrl,
+        dac_read_status
+};
+lpt_device_t lpt_dac_stereo_device =
+{
+        "Stereo LPT DAC",
+        dac_stereo_init,
+        dac_close,
+        dac_write_data,
+        dac_write_ctrl,
+        dac_read_status
+};