fork from https://github.com/mozilla/pdf.js.git

src/core/decrypt_stream.js

@@ -0,0 +1,55 @@
+/* Copyright 2012 Mozilla Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { DecodeStream } from "./decode_stream.js";
+
+const chunkSize = 512;
+
+class DecryptStream extends DecodeStream {
+  #nextChunk = null;
+
+  constructor(str, maybeLength, decrypt) {
+    super(maybeLength);
+
+    this.stream = str;
+    this.dict = str.dict;
+    this.decrypt = decrypt;
+  }
+
+  readBlock() {
+    let chunk = this.#nextChunk ?? this.stream.getBytes(chunkSize);
+    if (!chunk?.length) {
+      this.eof = true;
+      return;
+    }
+    this.#nextChunk = this.stream.getBytes(chunkSize);
+    const hasMoreData = this.#nextChunk?.length > 0;
+
+    const decrypt = this.decrypt;
+    chunk = decrypt(chunk, !hasMoreData);
+
+    const bufferLength = this.bufferLength,
+      newLength = bufferLength + chunk.length,
+      buffer = this.ensureBuffer(newLength);
+    buffer.set(chunk, bufferLength);
+    this.bufferLength = newLength;
+  }
+
+  getOriginalStream() {
+    return this;
+  }
+}
+
+export { DecryptStream };