add write cmd

- make custom plugins return ?Plugin instead of !Plugin

examples/write.scri

@@ -0,0 +1,3 @@
+load :0;
+write 3 1 1;
+quicksave;

src/custom.zig

@@ -15,14 +15,14 @@ pub const RandomNoise = struct {
     pub fn init(
         allocator: *std.mem.Allocator,
         params: *plugins.ParamMap,
-    ) !RandomNoise {
+    ) ?RandomNoise {
         const seed = @floatToInt(u64, params.get("seed").?.value);
         const fillbytes = @floatToInt(usize, params.get("fill_bytes").?.value);
 
         var r = std.rand.DefaultPrng.init(seed);
 
         if (fillbytes > 0) {
-            var rand_buf = try allocator.alloc(f32, fillbytes);
+            var rand_buf = allocator.alloc(f32, fillbytes) catch return null;
 
             for (rand_buf) |_, idx| {
                 rand_buf[idx] = r.random.float(f32);
@@ -59,14 +59,14 @@ pub const WildNoise = struct {
     pub fn init(
         allocator: *std.mem.Allocator,
         params: *plugins.ParamMap,
-    ) !WildNoise {
+    ) ?WildNoise {
         const seed = @floatToInt(u64, params.get("seed").?.value);
         const fillbytes = @floatToInt(usize, params.get("fill_bytes").?.value);
 
         var r = std.rand.DefaultPrng.init(seed);
 
         if (fillbytes > 0) {
-            var rand_buf = try allocator.alloc(f32, fillbytes);
+            var rand_buf = allocator.alloc(f32, fillbytes) catch return null;
 
             for (rand_buf) |_, idx| {
                 rand_buf[idx] = @intToFloat(f32, r.random.int(u1));
@@ -94,3 +94,22 @@ pub const WildNoise = struct {
         }
     }
 };
+
+pub const Write = struct {
+    data: f32,
+
+    pub fn init(
+        allocator: *std.mem.Allocator,
+        params: *plugins.ParamMap,
+    ) Write {
+        const data = params.get("data").?;
+
+        return Write{
+            .data = data.value,
+        };
+    }
+
+    pub fn run(self: *Write, bufs: *RunBuffers) void {
+        bufs.out[0] = self.data;
+    }
+};

src/image.zig

@@ -1,6 +1,7 @@
 const std = @import("std");
 const lv2 = @import("lv2_helpers.zig");
 const c = lv2.c;
+const custom = @import("custom.zig");
 
 const plugins = @import("plugin.zig");
 
@@ -17,6 +18,7 @@ pub const ImageError = error{
     InvalidSymbol,
     InstantiateFail,
     WriteFail,
+    PluginLoadFail,
 };
 
 /// Low level integration function with libsndfile.
@@ -358,7 +360,12 @@ pub const Image = struct {
         position: plugins.Position,
         params: *plugins.ParamMap,
     ) !void {
-        var plugin = try Plugin.init(self.allocator, params);
+        var plugin_opt: ?Plugin = Plugin.init(self.allocator, params);
+        if (plugin_opt == null) {
+            return ImageError.PluginLoadFail;
+        }
+
+        var plugin = plugin_opt.?;
 
         // the code here is a copypaste of runPlugin() without the specific
         // lilv things.

src/lang.zig

@@ -26,8 +26,10 @@ pub const CommandType = enum {
     Delay,
     Vinyl,
     RevDelay,
+
     Noise,
     WildNoise,
+    Write,
 
     Rotate,
 };
@@ -161,6 +163,7 @@ pub const Lang = struct {
         // custom implementations (not lv2)
         _ = try self.keywords.put("noise", .Noise);
         _ = try self.keywords.put("wildnoise", .WildNoise);
+        _ = try self.keywords.put("write", .Write);
 
         // even more custom
         _ = try self.keywords.put("rotate", .Rotate);

src/runner.zig

@@ -258,6 +258,11 @@ pub const Runner = struct {
         try image.runCustomPlugin(custom.WildNoise, pos, map);
     }
 
+    fn writeCmd(self: *Runner, pos: Position, map: *ParamMap) !void {
+        var image = try self.getImage();
+        try image.runCustomPlugin(custom.Write, pos, map);
+    }
+
     fn rotateCmd(
         self: *Runner,
         deg: f32,
@@ -431,6 +436,12 @@ pub const Runner = struct {
                 try self.wildNoiseCmd(pos, &map);
             },
 
+            .Write => blk: {
+                const pos = try cmd.consumePosition();
+                try cmd.appendParamMap(&map, "data");
+                try self.writeCmd(pos, &map);
+            },
+
             .Rotate => blk: {
                 const deg = try cmd.floatArgAt(0);
                 const bgfill = try cmd.argAt(1);