adding descriptor index to descriptor write

sandbox/main.zig

@@ -26,6 +26,8 @@ pub fn main() !void {
 
         var ssbo: SSBO = .{};
 
+        try rt.writeDescriptorSet(std.mem.asBytes(&ssbo), 0, 0, 0);
+
         for (0..16) |i| {
             for (0..16) |x| {
                 const global_invocation_indices = [3]i32{
@@ -35,7 +37,6 @@ pub fn main() !void {
                 };
 
                 try rt.writeBuiltIn(std.mem.asBytes(&global_invocation_indices), .GlobalInvocationId);
-                try rt.writeDescriptorSet(std.mem.asBytes(&ssbo), 0, 0);
                 rt.callEntryPoint(allocator, entry) catch |err| switch (err) {
                     spv.Runtime.RuntimeError.OutOfBounds => continue,
                     else => return err,

src/Runtime.zig

@@ -104,7 +104,8 @@ pub fn getResultByName(self: *const Self, name: []const u8) error{NotFound}!SpvW
 pub fn callEntryPoint(self: *Self, allocator: std.mem.Allocator, entry_point_index: SpvWord) RuntimeError!void {
     self.reset();
 
-    if (entry_point_index > self.mod.entry_points.items.len) return RuntimeError.InvalidEntryPoint;
+    if (entry_point_index > self.mod.entry_points.items.len)
+        return RuntimeError.InvalidEntryPoint;
 
     {
         const entry_point_desc = &self.mod.entry_points.items[entry_point_index];
@@ -151,9 +152,21 @@ pub fn callEntryPoint(self: *Self, allocator: std.mem.Allocator, entry_point_ind
     //}) catch return RuntimeError.OutOfMemory;
 }
 
-pub fn writeDescriptorSet(self: *const Self, input: []u8, set: SpvWord, binding: SpvWord) RuntimeError!void {
+pub fn writeDescriptorSet(self: *const Self, input: []u8, set: SpvWord, binding: SpvWord, descriptor_index: SpvWord) RuntimeError!void {
     if (set < lib.SPIRV_MAX_SET and binding < lib.SPIRV_MAX_SET_BINDINGS) {
-        _ = try self.results[self.mod.bindings[set][binding]].variant.?.Variable.value.write(input);
+        const value = &self.results[self.mod.bindings[set][binding]].variant.?.Variable.value;
+        switch (value.*) {
+            .Array => |arr| {
+                if (descriptor_index >= arr.len)
+                    return RuntimeError.NotFound;
+                _ = try arr[descriptor_index].write(input);
+            },
+            else => {
+                if (descriptor_index != 0)
+                    return RuntimeError.NotFound;
+                _ = try value.write(input);
+            },
+        }
     } else {
         return RuntimeError.NotFound;
     }

test/root.zig

@@ -54,7 +54,7 @@ pub const case = struct {
 
             for (config.descriptor_sets, 0..) |descriptor_set, set_index| {
                 for (descriptor_set, 0..) |descriptor_binding, binding_index| {
-                    try rt.writeDescriptorSet(descriptor_binding, @intCast(set_index), @intCast(binding_index));
+                    try rt.writeDescriptorSet(descriptor_binding, @intCast(set_index), @intCast(binding_index), 0);
                 }
             }