From 07de050588915e3b81d157598bc5476450953ceb Mon Sep 17 00:00:00 2001
From: C-3PO <c-3po@jedipedia.net>
Date: Thu, 5 Jul 2018 22:58:41 +0200
Subject: [PATCH] =?UTF-8?q?=F0=9F=90=9B=20Wait=20with=20reading=20local=20?=
 =?UTF-8?q?file=20header=20until=20stream=20is=20ready?=
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---
 src/ssn/getPatch.ts                    |  4 ++--
 src/ssn/streams/getFileFromDisks.ts    | 10 +++++-----
 src/ssn/streams/readLocalFileHeader.ts | 17 ++++++++++++++++-
 3 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/src/ssn/getPatch.ts b/src/ssn/getPatch.ts
index 7b96eff..a99f379 100644
--- a/src/ssn/getPatch.ts
+++ b/src/ssn/getPatch.ts
@@ -38,7 +38,7 @@ export default async function getPatch(product: Product, from: number, to: numbe
 
   //Extract newly added files
   fileEntries.filter((file) => file.diffType === SsnDiffType.NewFile).forEach(async (file) => {
-    const fileStream = getFileFromDisks(diskFilenames, { diskStart: file.diskNumberStart, offset: file.offset, storedSize: file.compressedSize });
+    const fileStream = await getFileFromDisks(diskFilenames, { diskStart: file.diskNumberStart, offset: file.offset, storedSize: file.compressedSize });
     const fileContents = extractFileStream(file, fileStream);
     console.debug(await streamToArrayBuffer(fileContents));
     //TODO: need to write to disk
@@ -46,7 +46,7 @@ export default async function getPatch(product: Product, from: number, to: numbe
 
   //Extract changed files
   fileEntries.filter((file) => file.diffType === SsnDiffType.Changed).forEach(async (file) => {
-    const fileStream = getFileFromDisks(diskFilenames, { diskStart: file.diskNumberStart, offset: file.offset, storedSize: file.compressedSize });
+    const fileStream = await getFileFromDisks(diskFilenames, { diskStart: file.diskNumberStart, offset: file.offset, storedSize: file.compressedSize });
     const fileContents = extractFileStream(file, fileStream);
     console.debug(await streamToArrayBuffer(fileContents));
     //TODO: need to apply diffing, then write to disk
diff --git a/src/ssn/streams/getFileFromDisks.ts b/src/ssn/streams/getFileFromDisks.ts
index e3f6b5c..6a949c6 100644
--- a/src/ssn/streams/getFileFromDisks.ts
+++ b/src/ssn/streams/getFileFromDisks.ts
@@ -16,7 +16,7 @@ function getStream(disks: string[], index: number, offset: number, length: numbe
 }
 
 /** 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 {
+export default async function getFileFromDisks(disks: string[], { diskStart, offset, storedSize }: IGetFileFromDisksOptions): Promise<stream.Readable> {
   let curDiskIndex = diskStart;
   let curDisk = getStream(disks, diskStart, offset);
   let localFileHeaderLength = 0;
@@ -56,6 +56,9 @@ export default function getFileFromDisks(disks: string[], { diskStart, offset, s
       //TODO
     }
   };
+  const onError = (error: any) => {
+    console.error(error);
+  };
   const onEnd = () => {
     curDiskIndex += 1;
     //End if we are at end of file or end of disks
@@ -69,16 +72,13 @@ export default function getFileFromDisks(disks: string[], { diskStart, offset, s
       curDisk.on('error', onError);
     }
   };
-  const onError = (error: any) => {
-    console.error(error);
-  };
 
   curDisk.on('data', onData);
   curDisk.on('end', onEnd);
   curDisk.on('error', onError);
 
   //Read local file header
-  localFileHeaderLength = readLocalFileHeader(outputStream);
+  localFileHeaderLength = await readLocalFileHeader(outputStream);
 
   //TODO: now that local file header has been read, restrict length of stream to storedSize
 
diff --git a/src/ssn/streams/readLocalFileHeader.ts b/src/ssn/streams/readLocalFileHeader.ts
index 35d2488..adc8eb5 100644
--- a/src/ssn/streams/readLocalFileHeader.ts
+++ b/src/ssn/streams/readLocalFileHeader.ts
@@ -1,10 +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 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 {
+export default async function readLocalFileHeader(inputStream: stream.Readable): Promise<number> {
+  //TODO: need to wait until
+  await waitReadableLength(inputStream, 30);
   const localFileHeader: Buffer = inputStream.read(30);
 
   //Local file header signature
@@ -21,6 +35,7 @@ export default function readLocalFileHeader(inputStream: stream.Readable): numbe
   //skip local file name and extra field
   const additionalLength = localFilenameSize + localExtraSize;
   if (additionalLength > 0) {
+    await waitReadableLength(inputStream, additionalLength);
     inputStream.read(additionalLength);
   }