prepare acquireDirect API

provide direct access to blip_buf to dispatch code, which may allow for some serious optimizations

src/engine/dispatch.h

@@ -23,6 +23,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include "../pch.h"
+#include "blip_buf.h"
 #include "config.h"
 #include "chipUtils.h"
 #include "defines.h"
@@ -587,6 +588,14 @@ class DivDispatch {
      */
     virtual void acquire(short** buf, size_t len);
 
+    /**
+     * fill a buffer with sound data (direct access to blip_buf).
+     * @param bb pointers to blip_buf instances.
+     * @param the offset to the first sample (use this when calling blip_add_delta).
+     * @param len the amount of samples to fill.
+     */
+    virtual void acquireDirect(blip_buffer_t** bb, size_t off, size_t len);
+
     /**
      * fill a write stream with data (e.g. for software-mixed PCM).
      * @param stream the write stream.
@@ -777,6 +786,12 @@ class DivDispatch {
      */
     virtual bool getWantPreNote();
 
+    /**
+     * check whether acquireDirect is available.
+     * @return whether it is.
+     */
+    virtual bool hasAcquireDirect();
+
     /**
      * get minimum chip clock.
      * @return clock in Hz, or 0 if custom clocks are not supported.

src/engine/platform/abstract.cpp

@@ -23,6 +23,9 @@
 void DivDispatch::acquire(short** buf, size_t len) {
 }
 
+void DivDispatch::acquireDirect(blip_buffer_t** bb, size_t off, size_t len) {
+}
+
 void DivDispatch::fillStream(std::vector<DivDelayedWrite>& stream, int sRate, size_t len) {
 }
 
@@ -127,6 +130,10 @@ bool DivDispatch::getDCOffRequired() {
   return false;
 }
 
+bool DivDispatch::hasAcquireDirect() {
+  return false;
+}
+
 bool DivDispatch::getWantPreNote() {
   return false;
 }