Improve boot sectore decoding

src/components/DiskInfo.vue

@@ -1,20 +1,18 @@
 <script lang="ts" setup>
 import { computed } from 'vue'
-import { getBiosParameterBlock } from '@/floppy/disk.ts'
-import PropertyList from '@/components/PropertyList.vue'
+import { decodeBootSector } from '@/floppy/disk.ts'
 
 const { data = new ArrayBuffer(0) } = defineProps<{ data: ArrayBuffer }>()
 
-const biosParameterBlock = computed(() => {
-  return getBiosParameterBlock(data)
+const bootSector = computed(() => {
+  return decodeBootSector(data)
 })
 </script>
 
 <template>
-  <section v-if="biosParameterBlock">
-    <h3>BIOS Parameter Block (BPB)</h3>
-    <PropertyList :obj="biosParameterBlock" />
-    <pre>{{ biosParameterBlock }}</pre>
+  <section v-if="bootSector">
+    <h3>Boot Sector</h3>
+    <pre>{{ bootSector }}</pre>
   </section>
 </template>
 

src/components/HexDump.vue

@@ -76,7 +76,7 @@ pre {
   width: fit-content;
   padding: 0.5em 1em 10em;
   box-sizing: border-box;
-  overflow: scroll;
+  overflow-y: scroll;
   min-height: 10rem;
   height: 20rem;
   max-height: 20rem;

src/floppy/disk.ts

@@ -1,61 +1,108 @@
-export interface BiosParameterBlock {
-  oemId: string
-  bytesPerSector: number
-  sectorsPerCluster: number
-  numReservedSectors: number
-  numFATs: number
-  numRootDirEntries: number
-  totalSectors: number
-  mediaTypeDescriptor: number
-  sectorsPerFAT: number
-  sectorsPerTrack: number
-  numHeads: number
-  bootSignature: number
-  volumeId: number
-  volumeLabel: string
-  fileSystemId: string
+export interface IBootSectorInfo {
+  jumpInstruction: [number, number, number]
+  oemName: string
+  biosParameterBlock: IBiosParameterBlock
+  extendedBootSector: IExtendedBootSectorSmall
+  bootPartitionSignature: number
 }
 
-export function getBiosParameterBlock(buffer: ArrayBuffer): BiosParameterBlock | null {
-  if (buffer.byteLength < 64) {
+export interface IExtendedBootSectorSmall {
+  driveNumber: number
+  reserved: number
+  bootSignature: number
+  volumeId?: number
+  volumeLabel?: string
+  fileSystemType?: string
+}
+
+export interface IBiosParameterBlock {
+  bytesPerSector: number
+  sectorsPerCluster: number
+  reservedSectorCount: number
+  tableCount: number
+  rootEntryCount: number
+  totalSectorsSmall: number
+  mediaDescriptorType: number
+  sectorsPerTableSmall: number
+  sectorsPerTrack: number
+  headCount: number
+  hiddenSectorCount: number
+  totalSectorsLarge: number
+}
+
+export function decodeBootSector(buffer: ArrayBuffer): IBootSectorInfo | null {
+  if (buffer.byteLength < 512) {
     return null
   }
 
+  const asciiDecoder = new TextDecoder('ascii')
   const data = new DataView(buffer)
 
-  const asciiDecoder = new TextDecoder('ascii')
+  const jumpInstruction: [number, number, number] = [
+    data.getUint8(0),
+    data.getUint8(1),
+    data.getUint8(2),
+  ]
 
-  const oemId = asciiDecoder.decode(buffer.slice(3, 11))
+  const oemName = asciiDecoder.decode(buffer.slice(3, 11))
   const bytesPerSector = data.getUint16(11, true)
   const sectorsPerCluster = data.getUint8(13)
-  const numReservedSectors = data.getUint16(14, true)
-  const numFATs = data.getUint8(16)
-  const numRootDirEntries = data.getUint16(17, true)
-  const totalSectors = data.getUint16(19, true)
-  const mediaTypeDescriptor = data.getUint8(21)
-  const sectorsPerFAT = data.getUint16(22, true)
+  const reservedSectorCount = data.getUint16(14, true)
+  const tableCount = data.getUint8(16)
+  const rootEntryCount = data.getUint16(17, true)
+  const totalSectorsSmall = data.getUint16(19, true)
+  const mediaDescriptorType = data.getUint8(21)
+  const sectorsPerTableSmall = data.getUint16(22, true)
   const sectorsPerTrack = data.getUint16(24, true)
-  const numHeads = data.getUint16(26, true)
+  const headCount = data.getUint16(26, true)
+  const hiddenSectorCount = data.getUint32(28, true)
+  const totalSectorsLarge = data.getUint32(32, true)
+  const driveNumber = data.getUint8(36)
+  const reserved = data.getUint8(37)
   const bootSignature = data.getUint8(38)
-  const volumeId = data.getUint32(39, true)
-  const volumeLabel = asciiDecoder.decode(buffer.slice(43, 54))
-  const fileSystemId = asciiDecoder.decode(buffer.slice(54, 62))
+
+  let volumeId
+  if (bootSignature === 0x28 || bootSignature === 0x29) {
+    volumeId = data.getUint32(39, true)
+  }
+
+  let volumeLabel
+  if (bootSignature === 0x29) {
+    volumeLabel = asciiDecoder.decode(buffer.slice(43, 54))
+  }
+
+  let fileSystemType
+  if (bootSignature === 0x29) {
+    fileSystemType = asciiDecoder.decode(buffer.slice(54, 62))
+  }
+
+  const bootPartitionSignature = data.getUint16(510, true)
 
   return {
-    oemId,
-    bytesPerSector,
-    sectorsPerCluster,
-    numReservedSectors,
-    numFATs,
-    numRootDirEntries,
-    totalSectors,
-    mediaTypeDescriptor,
-    sectorsPerFAT,
-    sectorsPerTrack,
-    numHeads,
-    bootSignature,
-    volumeId,
-    volumeLabel,
-    fileSystemId,
+    jumpInstruction,
+    oemName,
+    bootPartitionSignature,
+    biosParameterBlock: {
+      bytesPerSector,
+      sectorsPerCluster,
+      reservedSectorCount,
+      tableCount,
+      rootEntryCount,
+      totalSectorsSmall,
+      mediaDescriptorType,
+      sectorsPerTableSmall,
+      sectorsPerTrack,
+      headCount,
+      hiddenSectorCount,
+      totalSectorsLarge,
+    },
+    extendedBootSector: {
+      driveNumber,
+      reserved,
+      bootSignature,
+      volumeId,
+      volumeLabel,
+      fileSystemType,
+    },
   }
 }