🐛 Fix getFileFromDisks returning null due to not waiting for readable event

src/ssn/streams/getFileFromDisks.ts

@@ -11,33 +11,64 @@ interface IGetFileFromDisksOptions {
   storedSize: number;
 }
 
-function getStream(disks: string[], index: number, offset: number) {
-  return fs.createReadStream(disks[index], { start: offset });
+function getStream(disks: string[], index: number, offset: number, length: number = Infinity) {
+  return fs.createReadStream(disks[index], { start: offset, end: offset + length });
 }
 
 /** Takes a list of ReadableStreams (the disks), as well as the offset and length, and returns a stream for just one file. */
 export default function getFileFromDisks(disks: string[], { diskStart, offset, storedSize }: IGetFileFromDisksOptions): stream.Readable {
   let curDiskIndex = diskStart;
   let curDisk = getStream(disks, diskStart, offset);
+  let localFileHeaderLength = 0;
+  let totalRead = 0;
 
   //Create new stream that concatenates disks until storedSize is reached, then ends the stream.
-  const outputStream = new stream.Readable({
-    read(num) {
+  const outputStream = new stream.Duplex({
+    /*read(num) {
+      if (num === undefined) {
+        throw new Error('Expected to receive number of bytes when reading from stream.');
+      }
+
+      totalRead += num;
+      //end of file reached
+      if (localFileHeaderLength !== 0 && totalRead >= localFileHeaderLength + storedSize) {
+        return null;
+      }
+
       const chunk = curDisk.read(num);
       //transparently switch to next disk as soon as we finished reading current disk
       if (chunk === null) {
         curDiskIndex += 1;
-        curDisk = getStream(disks, curDiskIndex, 0);
-        //await new Promise((resolve) => { curDisk.on('readable', () => { resolve(); }); });
+        curDisk = getStream(disks, curDiskIndex, 0, (localFileHeaderLength === 0) ? Infinity : localFileHeaderLength + storedSize - totalRead);
+        //TODO: await new Promise((resolve) => { curDisk.on('readable', () => { resolve(); }); });
         return curDisk.read(num);
       } else {
         return chunk;
       }
-    },
+    },*/
   });
 
+  const onData = (chunk: Buffer) => {
+    outputStream.write(chunk);
+    totalRead += chunk.length;
+  };
+  const onEnd = () => {
+    curDiskIndex += 1;
+    if (curDiskIndex >= disks.length || (localFileHeaderLength !== 0 && totalRead >= localFileHeaderLength + storedSize)) {
+      outputStream.end();
+    } else {
+      curDisk = getStream(disks, curDiskIndex, 0, (localFileHeaderLength === 0) ? Infinity : localFileHeaderLength + storedSize - totalRead);
+      //set up new listeners for data and end
+      curDisk.on('data', onData);
+      curDisk.on('end', onEnd);
+    }
+  };
+
+  curDisk.on('data', onData);
+  curDisk.on('end', onEnd);
+
   //Read local file header
-  readLocalFileHeader(outputStream);
+  localFileHeaderLength = readLocalFileHeader(outputStream);
 
   //TODO: now that local file header has been read, restrict length of stream to storedSize
 

src/ssn/streams/readLocalFileHeader.ts

@@ -1,7 +1,10 @@
 import * as stream from 'stream';
 
-/** Reads the local file header, which is included before each stored file, and advances the stream accordingly. */
-export default function readLocalFileHeader(inputStream: stream.Readable) {
+/** 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 function readLocalFileHeader(inputStream: stream.Readable): number {
   const localFileHeader: Buffer = inputStream.read(30);
 
   //Local file header signature
@@ -16,7 +19,10 @@ export default function readLocalFileHeader(inputStream: stream.Readable) {
   const localExtraSize = localFileHeader.readUInt16LE(28);
 
   //skip local file name and extra field
-  if (localFilenameSize + localExtraSize > 0) {
-    inputStream.read(localFilenameSize + localExtraSize);
+  const additionalLength = localFilenameSize + localExtraSize;
+  if (additionalLength > 0) {
+    inputStream.read(additionalLength);
   }
+
+  return 30 + additionalLength;
 }