✨ Finish getFileFromDisks

src/ssn/streams/getFileFromDisks.ts

@@ -1,5 +1,6 @@
 import * as fs from 'fs';
 import * as stream from 'stream';
+import readLocalFileHeader from './readLocalFileHeader';
 
 interface IGetFileFromDisksOptions {
   /** Number of the disk where the local file header starts */
@@ -10,15 +11,34 @@ interface IGetFileFromDisksOptions {
   storedSize: number;
 }
 
+function getStream(disks: string[], index: number, offset: number) {
+  return fs.createReadStream(disks[index], { start: offset });
+}
+
 /** 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 {
-  const diskStreams = disks.map((fileName) => fs.createReadStream(fileName));
-  //TODO: Can local file header also be spread across multiple disks, or only the payload?
-  //Read local file header
-  //...
+  let curDiskIndex = diskStart;
+  let curDisk = getStream(disks, diskStart, offset);
 
   //Create new stream that concatenates disks until storedSize is reached, then ends the stream.
-  const outputStream = new stream.Readable();
-  //...
+  const outputStream = new stream.Readable({
+    read(num) {
+      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);
+        return curDisk.read(num);
+      } else {
+        return chunk;
+      }
+    },
+  });
+
+  //Read local file header
+  readLocalFileHeader(outputStream);
+
+  //TODO: now that local file header has been read, restrict length of stream to storedSize
+
   return outputStream;
 }