102 lines
3.7 KiB
Plaintext
102 lines
3.7 KiB
Plaintext
///////////////////////////////////////////////////////////////////////////////
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//
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// Microsoft Research Singularity
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//
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// Copyright (c) Microsoft Corporation. All rights reserved.
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//
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// File: FsInfo32.sg
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//
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// Note:
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//
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// Based on:
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// "Microsoft Extensible Firmware Initiative FAT32 File System Specification",
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// Version 1.03, December 6, 2000, Microsoft Corporation.
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//
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using System.Runtime.InteropServices;
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using Microsoft.Singularity.Io;
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namespace Microsoft.Singularity.Services.Fat.Fs
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{
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/// <remarks>
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/// FAT32 FsInfo sector structure. The FsInfo structure
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/// occupies a whole sector and contains information on the
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/// number of free blocks and the location of the first free
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/// block.
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/// </remarks>
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[StructLayout(LayoutKind.Explicit, Pack = 1, Size = 512)]
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internal pointerfree struct FsInfo32
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{
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///////////////////////////////////////////////////////////////////////
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// Constants
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internal const int Length = 512;
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internal const uint ExpectedLeadingSignature = 0x41615252;
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internal const uint ExpectedStructureSignature = 0x61417272;
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internal const uint ExpectedTrailingSignature = 0xaa550000;
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///////////////////////////////////////////////////////////////////////
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// Members
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[FieldOffset(000)] private uint leadingSignature; // 0
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// Reserved1 // 4..483
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[FieldOffset(484)] private uint structureSignature; // 484..487
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[FieldOffset(488)] private uint freeCount; // 488..491
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[FieldOffset(492)] private uint nextFree; // 492..495
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// Reserved2 // 496..507
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[FieldOffset(508)] private uint trailingSignature; // 508..511
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///////////////////////////////////////////////////////////////////////
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// Methods
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internal void Initialize(uint theFreeCount, uint theNextFree)
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{
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LeadingSignature = ExpectedLeadingSignature;
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StructureSignature = ExpectedStructureSignature;
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TrailingSignature = ExpectedTrailingSignature;
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FreeCount = theFreeCount;
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NextFree = theNextFree;
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}
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private uint LeadingSignature
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{
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get { return ByteOrder.LittleEndianToHost(leadingSignature); }
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set { leadingSignature = ByteOrder.HostToLittleEndian(value); }
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}
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private uint StructureSignature
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{
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get { return ByteOrder.LittleEndianToHost(structureSignature); }
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set { structureSignature = ByteOrder.HostToLittleEndian(value); }
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}
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internal uint FreeCount
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{
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get { return ByteOrder.LittleEndianToHost(freeCount); }
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set { freeCount = ByteOrder.HostToLittleEndian(value); }
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}
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internal uint NextFree
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{
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get { return ByteOrder.LittleEndianToHost(nextFree); }
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set { nextFree = ByteOrder.HostToLittleEndian(value); }
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}
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private uint TrailingSignature
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{
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get { return ByteOrder.LittleEndianToHost(trailingSignature); }
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set { trailingSignature = ByteOrder.HostToLittleEndian(value); }
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}
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[Microsoft.Contracts.Pure]
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internal bool ValidSignatures()
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{
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return (this.LeadingSignature == ExpectedLeadingSignature &&
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this.StructureSignature == ExpectedStructureSignature &&
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this.TrailingSignature == ExpectedTrailingSignature);
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}
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}
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}
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