🎨 Improve streamToString performance

src/ssn/decryption/decryptChunk.ts

@@ -27,11 +27,15 @@ export default function getDecryptor([key0, key1, key2]: [number, number, number
     const dvOut = new DataView(decryptedChunk.buffer);
 
     for (let i = 0; i < encryptedChunk.length; i += 1) {
-      //read and decrypt byte
+      //read byte
       let curChar = encryptedChunk.readUInt8(i);
+
+      //decrypt byte
       const keyPart = (key2 | 2) & 0xFFFF;
       const decryptedByte = (keyPart * (keyPart ^ 1)) >>> 8;
       curChar ^= decryptedByte & 0xFF;
+
+      //write byte
       if (position + i < 12) {
         //do nothing
       } else if (position + i >= 12 && position < 12) {

src/ssn/extractFileStream.ts

@@ -25,7 +25,9 @@ export default function extractFileStream(file: ISsnFileEntry, inputStream: stre
   const localExtraSize = localFileHeader.readUInt16LE(28);
 
   //skip local file name and extra field
-  inputStream.read(localFilenameSize + localExtraSize);
+  if (localFilenameSize + localExtraSize > 0) {
+    inputStream.read(localFilenameSize + localExtraSize);
+  }
 
   //-------------------------------------------------
 

src/ssn/streams/streamToString.ts

@@ -5,17 +5,17 @@ const decoder = new TextDecoder('utf-8');
 
 export default function streamToString(inputStream: stream.Readable): Promise<string> {
   return new Promise((resolve, reject) => {
-    let outputString = '';
+    const stringParts: string[] = [];
 
     //Convert chunks to string
     inputStream.on('data', (chunk: Buffer) => {
-      outputString += decoder.decode(chunk, { stream: true });
+      stringParts.push(decoder.decode(chunk, { stream: true }));
     });
 
     //Output final string
     inputStream.on('end', () => {
-      outputString += decoder.decode();
-      resolve(outputString);
+      stringParts.push(decoder.decode());
+      resolve(stringParts.join(''));
     });
 
     //Exit on error