From 0abcbc0d8cd489ea392004665437cbc818085e78 Mon Sep 17 00:00:00 2001
From: Jordan Goulder <jordan@jordangoulder.com>
Date: Fri, 17 Jan 2025 21:26:51 -0500
Subject: [PATCH] Improve performance by not reading file data ahead of time

---
 src/components/DiskInfo.vue       |  2 +-
 src/components/PlaygroundView.vue |  1 +
 src/floppy/disk.ts                | 17 ++++++-----------
 3 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/src/components/DiskInfo.vue b/src/components/DiskInfo.vue
index 8ed9c24..2180809 100644
--- a/src/components/DiskInfo.vue
+++ b/src/components/DiskInfo.vue
@@ -16,7 +16,7 @@ const fileListing = computed(() => {
 <template>
   <section v-if="floppyDisk.bootSectorInfo">
     <h3>File Listing</h3>
-    <div v-html="fileListing"></div>
+    <div v-memo="fileListing" v-html="fileListing"></div>
     <h3>Boot Sector</h3>
     <pre>{{ floppyDisk.bootSectorInfo }}</pre>
     <h3>Directory Entries</h3>
diff --git a/src/components/PlaygroundView.vue b/src/components/PlaygroundView.vue
index 4ae3c1c..3656ed1 100644
--- a/src/components/PlaygroundView.vue
+++ b/src/components/PlaygroundView.vue
@@ -19,6 +19,7 @@ function onReadStart(name: string) {
   diskName.value = name
   diskReadBytes.value = 0
   diskTotalBytes.value = -1
+  diskData.value = new ArrayBuffer(0)
 }
 
 function onReadSuccess(data: ArrayBuffer) {
diff --git a/src/floppy/disk.ts b/src/floppy/disk.ts
index cccf31f..806af76 100644
--- a/src/floppy/disk.ts
+++ b/src/floppy/disk.ts
@@ -47,7 +47,6 @@ export interface IStandardDirEntry {
   size: number
   firstCluster: number
   clusterChain: number[]
-  data: ArrayBuffer
   subDirEntries: TDirEntry[]
 }
 
@@ -174,6 +173,10 @@ export class FloppyDisk {
   }
 
   clusterChain(start: number): number[] {
+    if (start < 2) {
+      return []
+    }
+
     const chain = [start]
 
     let next = this.nextCluster(start)
@@ -337,15 +340,11 @@ function decodeDirectoryEntry(data: DataView, fd: FloppyDisk): TDirEntry | null
       attributes,
       firstCluster,
       clusterChain: [],
-      data: new Uint8Array(0),
       size,
       subDirEntries: [],
     }
 
-    if (
-      entry.size > 0 ||
-      (entry.attributes.directory && entry.name !== '.' && entry.name !== '..')
-    ) {
+    if (entry.attributes.directory && entry.name !== '.' && entry.name !== '..') {
       entry.clusterChain = fd.clusterChain(entry.firstCluster)
 
       const dataSize = entry.clusterChain.length * fd.bytesPerCluster
@@ -360,11 +359,7 @@ function decodeDirectoryEntry(data: DataView, fd: FloppyDisk): TDirEntry | null
 
         const resizedData = entryData.slice(0, entry.size > 0 ? entry.size : entryData.byteLength)
 
-        if (entry.attributes.directory) {
-          entry.subDirEntries = decodeDirectoryEntries(new DataView(resizedData.buffer), fd)
-        } else {
-          entry.data = resizedData
-        }
+        entry.subDirEntries = decodeDirectoryEntries(new DataView(resizedData.buffer), fd)
       }
     }