From 6d27dd9e7079e4b4d46d02a3f518f66e6dd5222b Mon Sep 17 00:00:00 2001
From: Sergey Linev <S.Linev@gsi.de>
Date: Wed, 21 Aug 2024 13:53:42 +0200
Subject: [PATCH] Fix - race in zstd initialization #318

While ZSTD decoding can be invoked
from different places, ensure that initialization performed properly.
---
 modules/io.mjs | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/modules/io.mjs b/modules/io.mjs
index dc72c7eff..4e3ff847b 100644
--- a/modules/io.mjs
+++ b/modules/io.mjs
@@ -2017,10 +2017,23 @@ async function R__unzip(arr, tgtsize, noalert, src_shift) {
          const tgt8arr = new Uint8Array(tgtbuf, fullres);
 
          if (fmt === 'ZSTD') {
-            const promise = internals._ZstdStream
-                            ? Promise.resolve(internals._ZstdStream)
-                            : (isNodeJs() ? import('@oneidentity/zstd-js') : import('./base/zstd.mjs'))
-                              .then(({ ZstdInit }) => ZstdInit()).then(({ ZstdStream }) => { internals._ZstdStream = ZstdStream; return ZstdStream; });
+            let promise;
+            if (internals._ZstdStream)
+               promise = Promise.resolve(internals._ZstdStream);
+            else if (internals._ZstdInit !== undefined)
+               promise = new Promise(resolveFunc => { internals._ZstdInit.push(resolveFunc); })
+            else {
+               internals._ZstdInit = [];
+               promise = (isNodeJs() ? import('@oneidentity/zstd-js') : import('./base/zstd.mjs'))
+                   .then(({ ZstdInit }) => ZstdInit())
+                   .then(({ ZstdStream }) => {
+                     internals._ZstdStream = ZstdStream;
+                     internals._ZstdInit.forEach(func => func(ZstdStream));
+                     delete internals._ZstdInit;
+                     return ZstdStream;
+                  });
+            }
+
             return promise.then(ZstdStream => {
                const data2 = ZstdStream.decompress(uint8arr),
                      reslen = data2.length;