gpu: add Buffer.Usage flagset

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

gpu/TODO-webgpu.h

@@ -1,21 +1,5 @@
 typedef uint32_t WGPUFlags;
 
-typedef enum WGPUBufferUsage {
-    WGPUBufferUsage_None = 0x00000000,
-    WGPUBufferUsage_MapRead = 0x00000001,
-    WGPUBufferUsage_MapWrite = 0x00000002,
-    WGPUBufferUsage_CopySrc = 0x00000004,
-    WGPUBufferUsage_CopyDst = 0x00000008,
-    WGPUBufferUsage_Index = 0x00000010,
-    WGPUBufferUsage_Vertex = 0x00000020,
-    WGPUBufferUsage_Uniform = 0x00000040,
-    WGPUBufferUsage_Storage = 0x00000080,
-    WGPUBufferUsage_Indirect = 0x00000100,
-    WGPUBufferUsage_QueryResolve = 0x00000200,
-    WGPUBufferUsage_Force32 = 0x7FFFFFFF
-} WGPUBufferUsage;
-typedef WGPUFlags WGPUBufferUsageFlags;
-
 typedef enum WGPUColorWriteMask {
     WGPUColorWriteMask_None = 0x00000000,
     WGPUColorWriteMask_Red = 0x00000001,

gpu/src/Buffer.zig

@@ -15,3 +15,31 @@ pub const MapAsyncStatus = enum(u32) {
     destroyed_before_callback = 0x00000004,
     unmapped_before_callback = 0x00000005,
 };
+
+pub const Usage = packed struct {
+    map_read: bool = false,
+    map_write: bool = false,
+    copy_src: bool = false,
+    copy_dst: bool = false,
+    index: bool = false,
+    vertex: bool = false,
+    uniform: bool = false,
+    storage: bool = false,
+    indirect: bool = false,
+    query_resolve: bool = false,
+
+    _pad0: u2 = 0,
+    _pad1: u8 = 0,
+    _pad2: u16 = 0,
+
+    comptime {
+        std.debug.assert(
+            @sizeOf(@This()) == @sizeOf(u32) and
+                @bitSizeOf(@This()) == @bitSizeOf(u32),
+        );
+    }
+
+    pub fn equal(a: Usage, b: Usage) bool {
+        return @bitCast(a, u32) == @bitCast(b, u32);
+    }
+};