add basic lilv instantiation support

- fix ampCmd's param pass

src/image.zig

@@ -1,12 +1,6 @@
 const std = @import("std");
 const lv2 = @import("lv2_helpers.zig");
-
-const c = @cImport({
-    @cInclude("sndfile.h");
-
-    @cInclude("lilv/lilv.h");
-    @cInclude("lv2/core/lv2.h");
-});
+const c = lv2.c;
 
 const plugins = @import("plugin.zig");
 
@@ -14,6 +8,8 @@ pub const ImageError = error{
     OpenFail,
     InvalidPlugin,
     UnknownPlugin,
+    InvalidSymbol,
+    InstantiateFail,
 };
 
 /// Low level integration function with libsndfile.
@@ -42,6 +38,48 @@ fn sopen(
     return file.?;
 }
 
+fn temporaryName(allocator: *std.mem.Allocator) ![]u8 {
+    const template_start = "/temp/temp_";
+    const template = "/tmp/temp_XXXXXX";
+    var nam = try allocator.alloc(u8, template.len);
+    std.mem.copy(u8, nam, template);
+
+    var r = std.rand.DefaultPrng.init(std.time.timestamp());
+
+    var fill = nam[template_start.len..nam.len];
+
+    var i: usize = 0;
+    while (i < 100) : (i += 1) {
+
+        // generate a random uppercase letter, that is, 65 + random number.
+        for (fill) |_, f_idx| {
+            var idx = @intCast(u8, r.random.uintLessThan(u5, 24));
+            var letter = u8(65) + idx;
+            fill[f_idx] = letter;
+        }
+
+        // if we fail to access it, we assume it doesn't exist and return it.
+        std.fs.File.access(nam) catch |err| {
+            if (err == error.FileNotFound) {
+                return nam;
+            }
+        };
+    }
+
+    return error.TempGenFail;
+}
+
+fn mkSfInfo() c.SF_INFO {
+    return c.SF_INFO{
+        .frames = c_int(0),
+        .samplerate = c_int(44100),
+        .channels = c_int(1),
+        .format = c.SF_FORMAT_ULAW | c.SF_FORMAT_RAW | c.SF_ENDIAN_BIG,
+        .sections = c_int(0),
+        .seekable = c_int(0),
+    };
+}
+
 pub const Image = struct {
     allocator: *std.mem.Allocator,
     sndfile: *c.SNDFILE,
@@ -49,14 +87,7 @@ pub const Image = struct {
 
     /// Open a BMP file.
     pub fn open(allocator: *std.mem.Allocator, path: []const u8) !*Image {
-        var in_fmt = c.SF_INFO{
-            .frames = c_int(0),
-            .samplerate = c_int(44100),
-            .channels = c_int(1),
-            .format = c.SF_FORMAT_ULAW | c.SF_FORMAT_RAW | c.SF_ENDIAN_BIG,
-            .sections = c_int(0),
-            .seekable = c_int(0),
-        };
+        var in_fmt = mkSfInfo();
 
         var sndfile = try sopen(allocator, path, c.SFM_READ, &in_fmt);
         var image = try allocator.create(Image);
@@ -97,19 +128,63 @@ pub const Image = struct {
         return n_read == 1;
     }
 
+    /// Run a plugin over the image.
+    /// This setups a new lilv world/plugin among other things.
+    /// The internal SNDFILE pointer is modified to point to the output of the
+    /// plugin run.
     pub fn runPlugin(
         self: *Image,
         plugin_uri: []const u8,
         pos: plugins.Position,
         params: plugins.ParamList,
     ) !void {
-        var context = try plugins.makeContext(self.allocator, plugin_uri);
-        std.debug.warn("world: {}\n", context.world);
-        std.debug.warn("plugin: {}\n", context.plugin);
+        var ctx = try plugins.makeContext(self.allocator, plugin_uri);
+        std.debug.warn("\tworld: {}\n", ctx.world);
+        std.debug.warn("\tplugin: {}\n", ctx.plugin);
 
-        var ports = try lv2.setupPorts(&context);
-        for (ports) |port| {
-            std.debug.warn("port: {}\n", port.*);
+        var ports = try lv2.setupPorts(&ctx);
+
+        if (ctx.n_audio_in != 1) {
+            std.debug.warn("plugin <{}> does not accept mono input.\n", plugin_uri);
+            return ImageError.InvalidPlugin;
         }
+
+        // now, for each param for the plugin, we find its port, and set
+        // the value for the port there.
+        var it = params.iterator();
+
+        while (it.next()) |param| {
+            var sym_cstr = try std.cstr.addNullByte(self.allocator, param.sym);
+            defer self.allocator.free(sym_cstr);
+
+            var sym = c.lilv_new_string(ctx.world, sym_cstr.ptr);
+            const port = c.lilv_plugin_get_port_by_symbol(ctx.plugin, sym) orelse blk: {
+                std.debug.warn("assert fail: symbol not found on port");
+                return ImageError.InvalidSymbol;
+            };
+
+            c.lilv_node_free(sym);
+
+            var idx = c.lilv_port_get_index(ctx.plugin, port);
+            std.debug.warn(
+                "sym={}, idx={} to val={}\n",
+                param.sym,
+                idx,
+                param.value,
+            );
+            ports[idx].value = param.value;
+        }
+
+        // now we need to generate a temporary file and put the output of
+        // running the plugin on that file
+        var tmpnam = try temporaryName(self.allocator);
+        std.debug.warn("temporary name: {}\n", tmpnam);
+
+        var out_fmt = mkSfInfo();
+        var out_file = try sopen(self.allocator, tmpnam, c.SFM_WRITE, &out_fmt);
+
+        var rctx = try plugins.RunContext.init(self.allocator, ctx.plugin);
+        rctx.connectPorts(ports);
+        lv2.lilv_instance_activate(rctx.instance);
     }
 };

src/lv2_helpers.zig

@@ -2,6 +2,7 @@ const std = @import("std");
 const plugin = @import("plugin.zig");
 
 pub const c = @cImport({
+    @cInclude("sndfile.h");
     @cInclude("lilv/lilv.h");
     @cInclude("lv2/core/lv2.h");
 });

src/plugin.zig

@@ -1,6 +1,7 @@
 const std = @import("std");
 
-const c = @import("lv2_helpers.zig").c;
+const lv2 = @import("lv2_helpers.zig");
+const c = lv2.c;
 
 const ImageError = @import("image.zig").ImageError;
 
@@ -26,13 +27,59 @@ pub const Position = struct {
 pub const Context = struct {
     allocator: *std.mem.Allocator,
     world: *c.LilvWorld,
-    plugin: ?*const c.LilvPlugin,
+    plugin: *const c.LilvPlugin,
 
     // they should both be 1.
     n_audio_in: usize = 0,
     n_audio_out: usize = 0,
 };
 
+/// Represents the specific run context of plugin instantation.
+pub const RunContext = struct {
+    in_buf: []f32,
+    out_buf: []f32,
+    instance: *c.LilvInstance,
+
+    pub fn init(
+        allocator: *std.mem.Allocator,
+        plugin: *const c.LilvPlugin,
+    ) !RunContext {
+        var instance = c.lilv_plugin_instantiate(plugin, f64(44100), null);
+        if (instance == null) {
+            return ImageError.InstantiateFail;
+        }
+
+        return RunContext{
+            .in_buf = try allocator.alloc(f32, 1),
+            .out_buf = try allocator.alloc(f32, 1),
+            .instance = instance.?,
+        };
+    }
+
+    pub fn connectPorts(self: *RunContext, ports: []*lv2.Port) void {
+        var i: usize = 0;
+        var o: usize = 0;
+
+        for (ports) |port, p_idx| {
+            var p = @intCast(u32, p_idx);
+
+            switch (port.ptype) {
+                .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, &self.in_buf[i]);
+                        i += 1;
+                    } else {
+                        lv2.lilv_instance_connect_port(self.instance, p, &self.out_buf[o]);
+                        o += 1;
+                    }
+                },
+                else => lv2.lilv_instance_connect_port(self.instance, p, null),
+            }
+        }
+    }
+};
+
 pub fn makeContext(allocator: *std.mem.Allocator, plugin_uri: []const u8) !Context {
     const cstr_plugin_uri = try std.cstr.addNullByte(allocator, plugin_uri);
     var world = c.lilv_world_new().?;

src/runner.zig

@@ -143,14 +143,14 @@ pub const Runner = struct {
     /// Run the http://lv2plug.in/plugins/eg-amp plugin over the file.
     fn ampCmd(self: *Runner, split: usize, index: usize, gain: f32) !void {
         var image = try self.getImage();
-        var param = try self.allocator.create(plugin.Param);
-        defer self.allocator.destroy(param);
-
-        param.* = plugin.Param{ .sym = "gain", .value = gain };
 
         var params = plugin.ParamList.init(self.allocator);
+        try params.append(plugin.Param{ .sym = "gain", .value = gain });
         defer params.deinit();
 
+        // TODO if we could detect that the next command is a quicksave then
+        // we don't need the temporary file in runPlugin and instead we
+        // dump it all on the output image for it.
         try image.runPlugin(
             "http://lv2plug.in/plugins/eg-amp",
             plugin.Position{ .split = split, .index = index },