works in dosbox

[dos_sbtest] / src / au_sb.c

diff --git a/src/au_sb.c b/src/au_sb.c
index ab12b9e..2046f91 100644 (file)
--- a/src/au_sb.c
+++ b/src/au_sb.c
@@ -3,6 +3,7 @@
 #include <pc.h>
 #include <go32.h>
 #include <dpmi.h>
+#include <sys/nearptr.h>
 #include "audio.h"
 #include "au_sb.h"
 #include "dma.h"
@@ -169,18 +170,28 @@ void *sb_buffer(int *size)
 
 void sb_start(int rate, int nchan)
 {
+       int seg, pmsel;
        uint32_t addr;
        int size;
        _go32_dpmi_seginfo intr;
 
-       /* for now just use the are after boot2. it's only used by the second stage
-        * loader and the VBE init code, none of which should overlap with audio playback.
-        * It's not necessary to use low memory. We can use up to the first 16mb for this,
-        * so if this becomes an issue, I'll make a DMA buffer allocator over 1mb.
-        * start the buffer from the next 64k boundary.
-        */
-       addr = ((uint32_t)low_mem_buffer + 0xffff) & 0xffff0000;
-       buffer = (void*)addr;
+       if(!buffer) {
+               __djgpp_nearptr_enable();
+
+               /* allocate a 64k-aligned 64k buffer in low memory */
+               if((seg = __dpmi_allocate_dos_memory(65536 * 2 / 16, &pmsel)) <= 0) {
+                       fprintf(stderr, "sb_start: failed to allocate DMA buffer\n");
+                       return;
+               }
+
+               printf("allocated seg: %d, addr: %lx\n", seg, (unsigned long)seg << 4);
+
+               addr = ((uint32_t)(seg << 4) + 0xffff) & 0xffff0000;
+               printf("aligned: %lx\n", (unsigned long)addr);
+               buffer = (void*)(addr - __djgpp_base_address);
+       } else {
+               addr = (uint32_t)buffer;
+       }
 
        xfer_mode = CMD_MODE_SIGNED;
        if(nchan > 1) {