perf(web): optimize Blob.text and Blob.arrayBuffer (#13981)

1 files changed, 18 insertions, 10 deletions

diff --git a/ext/web/09_file.js b/ext/web/09_file.js
index 2117a0835..50cce9004 100644
--- a/ext/web/09_file.js
+++ b/ext/web/09_file.js
@@ -340,8 +340,22 @@
      */
     async text() {
       webidl.assertBranded(this, BlobPrototype);
-      const buffer = await this.arrayBuffer();
-      return core.decode(new Uint8Array(buffer));
+      const buffer = await this.#u8Array(this.size);
+      return core.decode(buffer);
+    }
+
+    async #u8Array(size) {
+      const bytes = new Uint8Array(size);
+      const partIterator = toIterator(this[_parts]);
+      let offset = 0;
+      for await (const chunk of partIterator) {
+        const byteLength = chunk.byteLength;
+        if (byteLength > 0) {
+          TypedArrayPrototypeSet(bytes, chunk, offset);
+          offset += byteLength;
+        }
+      }
+      return bytes;
     }
 
     /**
@@ -349,14 +363,8 @@
      */
     async arrayBuffer() {
       webidl.assertBranded(this, BlobPrototype);
-      const stream = this.stream();
-      const bytes = new Uint8Array(this.size);
-      let offset = 0;
-      for await (const chunk of stream) {
-        TypedArrayPrototypeSet(bytes, chunk, offset);
-        offset += chunk.byteLength;
-      }
-      return bytes.buffer;
+      const buf = await this.#u8Array(this.size);
+      return buf.buffer;
     }
 
     [SymbolFor("Deno.customInspect")](inspect) {