From 8b1ad6f7e24c2a4af6f56d1ea69f90f04afa4d0b Mon Sep 17 00:00:00 2001
From: C-3PO <c-3po@jedipedia.net>
Date: Sun, 8 Jul 2018 19:09:31 +0200
Subject: [PATCH] =?UTF-8?q?=F0=9F=90=9B=20Fix=20race=20condition=20in=20fi?=
 =?UTF-8?q?le=20download?=
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---
 src/cdn/funcs/saveResponse.ts | 22 +++++++++-------------
 src/ssn/extractFileStream.ts  |  1 +
 src/ssn/getPatch.ts           |  1 +
 3 files changed, 11 insertions(+), 13 deletions(-)

diff --git a/src/cdn/funcs/saveResponse.ts b/src/cdn/funcs/saveResponse.ts
index 94e8ef8..f3f1ab5 100644
--- a/src/cdn/funcs/saveResponse.ts
+++ b/src/cdn/funcs/saveResponse.ts
@@ -15,9 +15,11 @@ export default function saveResponse(
   //Remember file size
   const headerLength = Number(response.headers['content-length']);
 
+  const writeStream = fs.createWriteStream(filePath);
+
   //If we receive a part of the response, write it to disk
-  let previousChunk: Promise<void> = new Promise((innerResolve) => { innerResolve(); });
   let totalLength = 0;
+  const chunkPromises: Array<Promise<void>> = [];
   response.on('data', (chunk: Buffer) => {
     totalLength += chunk.length;
 
@@ -26,18 +28,12 @@ export default function saveResponse(
       return reject(`Expected length ${headerLength} but received at least ${totalLength}.`);
     }
 
-    //If previous chunk was not yet written to disk, wait until it finished to avoid a race condition
-    previousChunk.then(() => {
-      previousChunk = new Promise((innerResolve, innerReject) => {
-        //Write chunk to disk
-        fs.appendFile(filePath, chunk, { encoding: 'binary' }, (error) => {
-          if (error) {
-            return reject(`Could not write to disk: [${error.code}] ${error.name}: ${error.message}.`);
-          }
-          innerResolve();
-        });
+    //Write chunk to disk
+    chunkPromises.push(new Promise((writeResolve) => {
+      writeStream.write(chunk, () => {
+        writeResolve();
       });
-    });
+    }));
   });
 
   //If we finished reading response, check for correctness, then return it
@@ -50,7 +46,7 @@ export default function saveResponse(
     //wait until everything is written to disk, then return file name
     //TODO: need to automatically delete file once it is no longer used
     //TODO: need to provide methods to seek through file
-    previousChunk.then(() => {
+    Promise.all(chunkPromises).then(() => {
       resolve(filePath);
     });
   });
diff --git a/src/ssn/extractFileStream.ts b/src/ssn/extractFileStream.ts
index a1eb4de..169cec0 100644
--- a/src/ssn/extractFileStream.ts
+++ b/src/ssn/extractFileStream.ts
@@ -24,6 +24,7 @@ export default function extractFileStream(file: ISsnFileEntry, inputStream: stre
   //pipe into decompression
   const decompressTransform = zlib.createInflateRaw();
   decompressTransform.on('error', (error) => {
+    //TODO: need to throw error sync, not async
     throw new Error(`Error during decompression: ${error.message}`);
   });
   curStream = curStream.pipe(decompressTransform);
diff --git a/src/ssn/getPatch.ts b/src/ssn/getPatch.ts
index e006503..fa64308 100644
--- a/src/ssn/getPatch.ts
+++ b/src/ssn/getPatch.ts
@@ -32,6 +32,7 @@ export default async function getPatch(product: Product, from: number, to: numbe
   //Then we need to wait for disks to finish download before we can extract individual files
   //TODO: we can optimize this to already extract some files as soon as their relevant parts are downloaded
   const diskFilenames = await Promise.all(diskFiles);
+  console.debug(diskFilenames);
   //const dvArray = bufferArray.map((buffer) => new DataView(buffer));
 
   //TODO: Verify that downloaded files match the hash in `solidpkg.pieces`