Fix O(n^2) slow fd_write

[TerrorJack]

Closes #93. Note that I've also taken some time to upgrade all the outdated dependencies and fix the code accordingly, if you wouldn't mind.

[bjorn3]

Please move the dependency updates to a separate commit and skip the version bump commit.

[bjorn3]

I meant separate PR, not commit. My bad.

[TerrorJack]

At the very least, typescript must be bumped, otherwise the baseline 2024 arraybuffer grow type signature as well as the Uint8Array<ArrayBuffer> type would not be available at all. So it's not really feasible to spin out only the changes here and make it typecheck without any bumps.

[bjorn3]

The dependency bump PR could be merged first.

[bjorn3]

LGTM with the following patch (can't push to your branch) Apologies for the long wait.

Author: bjorn3 <17426603+bjorn3@users.noreply.github.com>
Date:   Sun Jan 18 22:48:44 2026 +0100

    Minor style changes

diff --git a/src/fs_mem.ts b/src/fs_mem.ts
index 4399ee6..0551259 100644
--- a/src/fs_mem.ts
+++ b/src/fs_mem.ts
@@ -24,9 +24,9 @@ function dataResize(data: Uint8Array, newDataSize: number): Uint8Array {
   // of old data onto it
   if (data.byteLength > newDataSize) {
     const newBuffer = new ArrayBuffer(newDataSize, {
-        maxByteLength: newDataSize,
-      }),
-      newData = new Uint8Array(newBuffer);
+      maxByteLength: newDataSize,
+    });
+    const newData = new Uint8Array(newBuffer);
     newData.set(new Uint8Array(data.buffer, 0, newDataSize));
     return newData;
   }
@@ -35,9 +35,9 @@ function dataResize(data: Uint8Array, newDataSize: number): Uint8Array {
   // growth of maxByteLength, to avoid O(n^2) overhead of repeatedly
   // concatenating buffers when doing a lot of small writes at the end
   const newBuffer = new ArrayBuffer(newDataSize, {
-      maxByteLength: Math.max(newDataSize, data.buffer.maxByteLength * 2),
-    }),
-    newData = new Uint8Array(newBuffer);
+    maxByteLength: Math.max(newDataSize, data.buffer.maxByteLength * 2),
+  });
+  const newData = new Uint8Array(newBuffer);
   newData.set(data);
   return newData;
 }

[TerrorJack]

Apologies for the long wait.

oh never mind! we have our own fork https://github.com/haskell-wasm/browser_wasi_shim anyway, with the intention of gradually upstreaming our fixes, and upstream reviewer should review patches at their own pace without any pressure. again, thank you for this wonderful project :)

[bjorn3]

Thanks!

[bjorn3]

Are there more changes you did like to make? If not I can do a release later today.

[TerrorJack]

yes, there are some other changes that i'd like to open PRs tomorrow or so, if you're not in a hurry.