1 files changed, 68 insertions, 0 deletions
diff --git a/dom/webgpu/tests/cts/checkout/src/webgpu/util/texture/subresource.ts b/dom/webgpu/tests/cts/checkout/src/webgpu/util/texture/subresource.ts
new file mode 100644
index 0000000000..b8d6e3eb21
--- /dev/null
+++ b/dom/webgpu/tests/cts/checkout/src/webgpu/util/texture/subresource.ts
@@ -0,0 +1,68 @@
+/** A range of indices expressed as `{ begin, count }`. */
+export interface BeginCountRange {
+  begin: number;
+  count: number;
+}
+
+/* A range of indices, expressed as `{ begin, end }`. */
+export interface BeginEndRange {
+  begin: number;
+  end: number;
+}
+
+function endOfRange(r: BeginEndRange | BeginCountRange): number {
+  return 'count' in r ? r.begin + r.count : r.end;
+}
+
+function* rangeAsIterator(r: BeginEndRange | BeginCountRange): Generator<number> {
+  for (let i = r.begin; i < endOfRange(r); ++i) {
+    yield i;
+  }
+}
+
+/**
+ * Represents a range of subresources of a single-plane texture:
+ * a min/max mip level and min/max array layer.
+ */
+export class SubresourceRange {
+  readonly mipRange: BeginEndRange;
+  readonly layerRange: BeginEndRange;
+
+  constructor(subresources: {
+    mipRange: BeginEndRange | BeginCountRange;
+    layerRange: BeginEndRange | BeginCountRange;
+  }) {
+    this.mipRange = {
+      begin: subresources.mipRange.begin,
+      end: endOfRange(subresources.mipRange),
+    };
+    this.layerRange = {
+      begin: subresources.layerRange.begin,
+      end: endOfRange(subresources.layerRange),
+    };
+  }
+
+  /**
+   * Iterates over the "rectangle" of `{ level, layer }` pairs represented by the range.
+   */
+  *each(): Generator<{ level: number; layer: number }> {
+    for (let level = this.mipRange.begin; level < this.mipRange.end; ++level) {
+      for (let layer = this.layerRange.begin; layer < this.layerRange.end; ++layer) {
+        yield { level, layer };
+      }
+    }
+  }
+
+  /**
+   * Iterates over the mip levels represented by the range, each level including an iterator
+   * over the array layers at that level.
+   */
+  *mipLevels(): Generator<{ level: number; layers: Generator<number> }> {
+    for (let level = this.mipRange.begin; level < this.mipRange.end; ++level) {
+      yield {
+        level,
+        layers: rangeAsIterator(this.layerRange),
+      };
+    }
+  }
+}