From 519eb51206036098d8e63e62735b003efccaa0a5 Mon Sep 17 00:00:00 2001
From: Luna <git@l4.pm>
Date: Sat, 25 Jan 2020 22:46:00 -0300
Subject: [PATCH] remove heap allocation for RunBuffers

---
 src/image.zig  | 27 ++++++++++++++++-----------
 src/plugin.zig | 46 ++++++++++++++++------------------------------
 2 files changed, 32 insertions(+), 41 deletions(-)

diff --git a/src/image.zig b/src/image.zig
index ad48f61..9541070 100644
--- a/src/image.zig
+++ b/src/image.zig
@@ -370,18 +370,25 @@ pub const Image = struct {
         var i: usize = seek_pos.start;
         std.debug.warn("\tseek pos start: {} end: {}\n", .{ seek_pos.start, seek_pos.end });
 
-        var inbuf = rctx.buffers.in;
-        var outbuf = rctx.buffers.out;
+        var inbuf = &rctx.buffers.in;
+        var outbuf = &rctx.buffers.out;
 
         while (i <= seek_pos.end) : (i += 1) {
-            const read_bytes = c.sf_readf_float(self.sndfile, inbuf.ptr, 1);
+            inbuf[0] = 0;
+            inbuf[1] = 0;
+
+            const read_bytes = c.sf_readf_float(self.sndfile, inbuf, 1);
             if (read_bytes == 0) {
                 std.debug.warn("WARN! reached EOF at idx={}\n", .{i});
                 break;
             }
 
+            // trick plugins into having correct stereo signal from
+            // my mono input
+            inbuf[1] = inbuf[0];
+
             lv2.lilv_instance_run(rctx.instance, 1);
-            try swrite(out_file, outbuf.ptr, 1);
+            try swrite(out_file, outbuf, 1);
         }
 
         sseek(self.sndfile, seek_pos.end);
@@ -439,9 +446,7 @@ pub const Image = struct {
         var out_fmt = mkSfInfo();
         var out_file = try sopen(self.allocator, tmpnam, c.SFM_WRITE, &out_fmt);
 
-        var bufs = try plugins.RunBuffers.init(self.allocator);
-        defer bufs.deinit();
-
+        var bufs = plugins.RunBuffers{};
         const seek_pos = self.getSeekPos(position);
 
         // make sure we start from 0
@@ -465,18 +470,18 @@ pub const Image = struct {
         var i: usize = seek_pos.start;
         std.debug.warn("\tseek pos start: {} end: {}\n", .{ seek_pos.start, seek_pos.end });
 
-        var inbuf = bufs.in;
-        var outbuf = bufs.out;
+        var inbuf = &bufs.in;
+        var outbuf = &bufs.out;
 
         while (i <= seek_pos.end) : (i += 1) {
-            const read_bytes = c.sf_readf_float(self.sndfile, bufs.in.ptr, 1);
+            const read_bytes = c.sf_readf_float(self.sndfile, inbuf, 1);
             if (read_bytes == 0) {
                 std.debug.warn("WARN! reached EOF at idx={}\n", .{i});
                 break;
             }
 
             plugin.run(&bufs);
-            try swrite(out_file, bufs.out.ptr, 1);
+            try swrite(out_file, outbuf, 1);
         }
 
         sseek(self.sndfile, seek_pos.end);
diff --git a/src/plugin.zig b/src/plugin.zig
index 6c98336..b979833 100644
--- a/src/plugin.zig
+++ b/src/plugin.zig
@@ -61,29 +61,11 @@ pub const Context = struct {
 
 /// Specific run context for non-plugins.
 pub const RunBuffers = struct {
-    allocator: *std.mem.Allocator,
-
-    in: []f32,
-    out: []f32,
-
-    pub fn init(allocator: *std.mem.Allocator) !RunBuffers {
-        // we allocate []f32 with size 2 to account for stereo plugins, however
-        // we only use &in_buf[0] and &out_buf[0], and don't use the
-        // (supposedly) right side of neither input or output.
-        var in_buf = try allocator.alloc(f32, 2);
-        std.mem.secureZero(f32, in_buf);
-
-        return RunBuffers{
-            .allocator = allocator,
-            .in = in_buf,
-            .out = try allocator.alloc(f32, 2),
-        };
-    }
-
-    pub fn deinit(self: *RunBuffers) void {
-        self.allocator.free(self.in);
-        self.allocator.free(self.out);
-    }
+    // we use [2]f32 to account for stereo plugins, however
+    // we only use in_buf[0] and out_buf[0], and don't use the
+    // (supposedly) right side of neither input or output.
+    in: [2]f32 = [_]f32{0} ** 2,
+    out: [2]f32 = [_]f32{0} ** 2,
 };
 
 /// Represents the specific run context of plugin instantation.
@@ -103,23 +85,19 @@ pub const RunContext = struct {
         }
 
         return RunContext{
-            .buffers = try RunBuffers.init(allocator),
+            .buffers = RunBuffers{},
             .instance = instance.?,
         };
     }
 
     pub fn deinit(self: *RunContext) void {
         c.lilv_instance_free(self.instance);
-        self.buffers.deinit();
     }
 
     pub fn connectPorts(self: *RunContext, ports: []lv2.Port) void {
         var i: usize = 0;
         var o: usize = 0;
 
-        var in_buf = self.buffers.in;
-        var out_buf = self.buffers.out;
-
         for (ports) |_, p_idx| {
             var p = @intCast(u32, p_idx);
             var port: *lv2.Port = &ports[p_idx];
@@ -128,10 +106,18 @@ pub const RunContext = struct {
                 .Control => lv2.lilv_instance_connect_port(self.instance, p, &port.value),
                 .Audio => blk: {
                     if (port.is_input) {
-                        lv2.lilv_instance_connect_port(self.instance, p, &in_buf[i]);
+                        lv2.lilv_instance_connect_port(
+                            self.instance,
+                            p,
+                            &self.buffers.in[i],
+                        );
                         i += 1;
                     } else {
-                        lv2.lilv_instance_connect_port(self.instance, p, &out_buf[o]);
+                        lv2.lilv_instance_connect_port(
+                            self.instance,
+                            p,
+                            &self.buffers.out[o],
+                        );
                         o += 1;
                     }
                 },