♻ Extract waiting for stream to be readable

src/ssn/extractFileStream.ts

@@ -4,7 +4,7 @@ import * as stream from 'stream';
 import * as zlib from 'zlib';
 import { ISsnFileEntry } from '../interfaces/ISsnFileEntry';
 import decryptStream from './streams/decryptStream';
-import waitReadableLength from './streams/waitReadableLength';
+import readBytesFromStream from './streams/readBytesFromStream';
 
 /** Extracts the file with the given metadata from the stream.
  * The stream must already start at the .zip's local file header
@@ -18,12 +18,7 @@ export default async function extractFileStream(file: ISsnFileEntry, inputStream
     const decryptTransform = decryptStream(file.decryptionKeys);
     curStream = curStream.pipe(decryptTransform);
     //skip encryption header
-    const encryptionHeader = curStream.read(12);
-    if (encryptionHeader === null) {
-      //need to wait until data is ready for reading
-      await waitReadableLength(curStream, 12);
-      curStream.read(12);
-    }
+    readBytesFromStream(curStream, 12);
   }
 
   if (!skipDecompression) {

src/ssn/streams/readBytesFromStream.ts

@@ -0,0 +1,24 @@
+import * as stream from 'stream';
+
+/** Returns a promise that resolves as soon as the given stream has the given number of bytes ready for reading. */
+function waitReadableLength(inputStream: stream.Readable, minLength: number): Promise<void> {
+  return new Promise((resolve) => {
+    const interval = setInterval(() => {
+      if (inputStream.readableLength >= minLength) {
+        clearInterval(interval);
+        resolve();
+      }
+    }, 100);
+  });
+}
+
+/** Reads the given number of bytes from the stream and returns them as a buffer, optionally waiting until the bytes are ready for reading. */
+export default async function readBytesFromStream(inputStream: stream.Readable, length: number): Promise<Buffer> {
+  let localFileHeader: Buffer = inputStream.read(length);
+  while (localFileHeader === null) {
+    //need to wait until data is ready for reading
+    await waitReadableLength(inputStream, length);
+    localFileHeader = inputStream.read(length);
+  }
+  return localFileHeader;
+}

src/ssn/streams/readLocalFileHeader.ts

@@ -1,17 +1,12 @@
 import * as stream from 'stream';
-import waitReadableLength from './waitReadableLength';
+import readBytesFromStream from './readBytesFromStream';
 
 /** Reads the local file header, which is included before
  * each stored file, and advances the stream accordingly.
  * Returns length of the local file header.
  */
 export default async function readLocalFileHeader(inputStream: stream.Readable, skipAdditionalLength = false): Promise<number> {
-  let localFileHeader: Buffer = inputStream.read(30);
-  if (localFileHeader === null) {
-    //need to wait until data is ready for reading
-    await waitReadableLength(inputStream, 30);
-    localFileHeader = inputStream.read(30);
-  }
+  const localFileHeader = await readBytesFromStream(inputStream, 30);
 
   //Local file header signature
   const magic = localFileHeader.readUInt32LE(0);
@@ -27,13 +22,7 @@ export default async function readLocalFileHeader(inputStream: stream.Readable,
   //skip local file name and extra field
   const additionalLength = localFilenameSize + localExtraSize;
   if (skipAdditionalLength && additionalLength > 0) {
-    await waitReadableLength(inputStream, additionalLength);
-    const tmpChunk = inputStream.read(additionalLength);
-    if (tmpChunk === null) {
-      //need to wait until data is ready for reading
-    await waitReadableLength(inputStream, additionalLength);
-    inputStream.read(additionalLength);
-    }
+    await readBytesFromStream(inputStream, additionalLength);
   }
 
   return 30 + additionalLength;

src/ssn/streams/waitReadableLength.ts

@@ -1,13 +0,0 @@
-import * as stream from 'stream';
-
-/** Returns a promise that resolves as soon as the given stream has the given number of bytes ready for reading. */
-export default function waitReadableLength(inputStream: stream.Readable, minLength: number): Promise<void> {
-  return new Promise((resolve) => {
-    const interval = setInterval(() => {
-      if (inputStream.readableLength >= minLength) {
-        clearInterval(interval);
-        resolve();
-      }
-    }, 100);
-  });
-}