Move the arrayBuffersToBytes helper function into the worker-thread

Given that this helper function is only used on the worker-thread, there's no reason to duplicate it in both of the *built* `pdf.js` and `pdf.worker.js` files.

src/core/chunked_stream.js

@@ -13,12 +13,8 @@
  * limitations under the License.
  */
 
-import {
+import { arrayBuffersToBytes, MissingDataException } from "./core_utils.js";
-  arrayBuffersToBytes,
+import { assert, createPromiseCapability } from "../shared/util.js";
-  assert,
-  createPromiseCapability,
-} from "../shared/util.js";
-import { MissingDataException } from "./core_utils.js";
 import { Stream } from "./stream.js";
 
 class ChunkedStream extends Stream {

src/core/core_utils.js

@@ -80,6 +80,44 @@ class XRefParseException extends BaseException {
   }
 }
 
+/**
+ * Combines multiple ArrayBuffers into a single Uint8Array.
+ * @param {Array<ArrayBuffer>} arr - An array of ArrayBuffers.
+ * @returns {Uint8Array}
+ */
+function arrayBuffersToBytes(arr) {
+  if (
+    typeof PDFJSDev === "undefined" ||
+    PDFJSDev.test("!PRODUCTION || TESTING")
+  ) {
+    for (const item of arr) {
+      assert(
+        item instanceof ArrayBuffer,
+        "arrayBuffersToBytes - expected an ArrayBuffer."
+      );
+    }
+  }
+  const length = arr.length;
+  if (length === 0) {
+    return new Uint8Array(0);
+  }
+  if (length === 1) {
+    return new Uint8Array(arr[0]);
+  }
+  let dataLength = 0;
+  for (let i = 0; i < length; i++) {
+    dataLength += arr[i].byteLength;
+  }
+  const data = new Uint8Array(dataLength);
+  let pos = 0;
+  for (let i = 0; i < length; i++) {
+    const item = new Uint8Array(arr[i]);
+    data.set(item, pos);
+    pos += item.byteLength;
+  }
+  return data;
+}
+
 /**
  * Get the value of an inheritable property.
  *
@@ -579,6 +617,7 @@ function getRotationMatrix(rotation, width, height) {
 }
 
 export {
+  arrayBuffersToBytes,
   collectActions,
   encodeToXmlString,
   escapePDFName,

src/core/worker.js

@@ -15,7 +15,6 @@
 
 import {
   AbortException,
-  arrayBuffersToBytes,
   assert,
   createPromiseCapability,
   getVerbosityLevel,
@@ -30,8 +29,12 @@ import {
   VerbosityLevel,
   warn,
 } from "../shared/util.js";
+import {
+  arrayBuffersToBytes,
+  getNewAnnotationsMap,
+  XRefParseException,
+} from "./core_utils.js";
 import { Dict, Ref } from "./primitives.js";
-import { getNewAnnotationsMap, XRefParseException } from "./core_utils.js";
 import { LocalPdfManager, NetworkPdfManager } from "./pdf_manager.js";
 import { clearGlobalCaches } from "./cleanup_helper.js";
 import { incrementalUpdate } from "./writer.js";

src/shared/util.js

@@ -597,44 +597,6 @@ function stringToBytes(str) {
   return bytes;
 }
 
-/**
- * Combines multiple ArrayBuffers into a single Uint8Array.
- * @param {Array<ArrayBuffer>} arr - An array of ArrayBuffers.
- * @returns {Uint8Array}
- */
-function arrayBuffersToBytes(arr) {
-  if (
-    typeof PDFJSDev === "undefined" ||
-    PDFJSDev.test("!PRODUCTION || TESTING")
-  ) {
-    for (const item of arr) {
-      assert(
-        item instanceof ArrayBuffer,
-        "arrayBuffersToBytes - expected an ArrayBuffer."
-      );
-    }
-  }
-  const length = arr.length;
-  if (length === 0) {
-    return new Uint8Array(0);
-  }
-  if (length === 1) {
-    return new Uint8Array(arr[0]);
-  }
-  let dataLength = 0;
-  for (let i = 0; i < length; i++) {
-    dataLength += arr[i].byteLength;
-  }
-  const data = new Uint8Array(dataLength);
-  let pos = 0;
-  for (let i = 0; i < length; i++) {
-    const item = new Uint8Array(arr[i]);
-    data.set(item, pos);
-    pos += item.byteLength;
-  }
-  return data;
-}
-
 function string32(value) {
   if (
     typeof PDFJSDev === "undefined" ||
@@ -1103,7 +1065,6 @@ export {
   AnnotationReviewState,
   AnnotationStateModelType,
   AnnotationType,
-  arrayBuffersToBytes,
   assert,
   BaseException,
   BASELINE_FACTOR,

test/unit/core_utils_spec.js

@@ -13,8 +13,8 @@
  * limitations under the License.
  */
 
-import { Dict, Ref } from "../../src/core/primitives.js";
 import {
+  arrayBuffersToBytes,
   encodeToXmlString,
   escapePDFName,
   escapeString,
@@ -30,9 +30,36 @@ import {
   toRomanNumerals,
   validateCSSFont,
 } from "../../src/core/core_utils.js";
+import { Dict, Ref } from "../../src/core/primitives.js";
 import { XRefMock } from "./test_utils.js";
 
 describe("core_utils", function () {
+  describe("arrayBuffersToBytes", function () {
+    it("handles zero ArrayBuffers", function () {
+      const bytes = arrayBuffersToBytes([]);
+
+      expect(bytes).toEqual(new Uint8Array(0));
+    });
+
+    it("handles one ArrayBuffer", function () {
+      const buffer = new Uint8Array([1, 2, 3]).buffer;
+      const bytes = arrayBuffersToBytes([buffer]);
+
+      expect(bytes).toEqual(new Uint8Array([1, 2, 3]));
+      // Ensure that the fast-path works correctly.
+      expect(bytes.buffer).toBe(buffer);
+    });
+
+    it("handles multiple ArrayBuffers", function () {
+      const buffer1 = new Uint8Array([1, 2, 3]).buffer,
+        buffer2 = new Uint8Array(0).buffer,
+        buffer3 = new Uint8Array([4, 5]).buffer;
+      const bytes = arrayBuffersToBytes([buffer1, buffer2, buffer3]);
+
+      expect(bytes).toEqual(new Uint8Array([1, 2, 3, 4, 5]));
+    });
+  });
+
   describe("getInheritableProperty", function () {
     it("handles non-dictionary arguments", function () {
       expect(getInheritableProperty({ dict: null, key: "foo" })).toEqual(