luaproc: assert instance access

scripts/amp2.lua

@@ -34,8 +34,17 @@ end
 
 function dsp_runmap (bufs, in_map, out_map, n_samples, offset)
 	for c = 1,audio_ins do
-		local b = in_map:get(ARDOUR.DataType("audio"), c - 1); -- get id of mapped buffer
+		-- ensure that processing does happen in-place
-		local a = bufs:get_audio(b):data(offset):array() -- get a reference (pointer to array)
+		local ib = in_map:get(ARDOUR.DataType("audio"), c - 1); -- get id of mapped input buffer for given cannel
+		local ob = out_map:get(ARDOUR.DataType("audio"), c - 1); -- get id of mapped output buffer for given cannel
+		assert (ib ~= ARDOUR.ChanMapping.Invalid);
+		assert (ob ~= ARDOUR.ChanMapping.Invalid);
+
+		local bi = bufs:get_audio(ib)
+		local bo = bufs:get_audio(ob)
+		assert (bi:sameinstance(bo))
+
+		local a = bufs:get_audio(ib):data(offset):array() -- get a reference (pointer to array)
 		for s = 1,n_samples do
 			a[s] = a[s] * 2; -- modify data in-place (shared with ardour)
 		end

scripts/amp3.lua

@@ -31,15 +31,15 @@ end
 -- This is as efficient as Ardour doing it itself in C++
 -- Lua function overhead is negligible
 --
--- this also exemplifies the /simpler/ way of letting ardour to
+-- this also exemplifies the /simpler/ way of delegating the
--- the channel and offset mapping.
+-- channel-mapping to ardour.
 
 function dsp_run (ins, outs, n_samples)
 	local ctrl = CtrlPorts:array() -- get control port array (read/write)
 	local gain = ARDOUR.DSP.dB_to_coefficient (ctrl[1])
-	assert (#ins == #outs) -- ensure that we can run in-place
+	assert (#ins == #outs) -- ensure that we can run in-place (channel count matches)
 	for c = 1,#ins do
-	--for c in pairs (ins) do -- also works, slightly less effective
+		assert (ins[c]:sameinstance(outs[c])) -- check in-place
 		ARDOUR.DSP.apply_gain_to_buffer (ins[c], n_samples, gain); -- process in-place
 	end
 end