80 lines
3.2 KiB
Plaintext
80 lines
3.2 KiB
Plaintext
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///////////////////////////////////////////////////////////////////////////////
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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: Fat.sg
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//
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// TODO: Block allocation for sequential cluster groups. This
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// would entail less buffer cache lock operations.
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//
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using Microsoft.SingSharp;
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using Microsoft.Singularity.Io;
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using Microsoft.Singularity.Channels;
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using System;
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namespace Microsoft.Singularity.Services.Fat.Fs
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{
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internal abstract class Fat
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{
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/// <summary> Largest number of clusters that can be allocated
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/// at a time.
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/// </summary>
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public const int MaxAllocationLength = Bitmap.MaxAllocationLength;
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/// <summary> Allocate cluster chain. The allocation is
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/// no guaranteed to be contiguous</summary>
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/// <returns> true if some of the requested clusters
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/// have been allocated, false if there were no free
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/// clusters available. </returns>
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internal abstract bool AllocateChain(int hintClusterArea,
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int targetLength,
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out int allocStart,
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out int allocLength);
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/// <summary> Frees the chain starting at specified offset </summary>
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internal abstract void FreeChain(int startCluster);
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/// <summary> Grow an existing cluster chain. The allocation is
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/// not guaranteed to be contiguous.</summary>
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/// <returns> true if some of the requested clusters
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/// have been allocated, false if there were no free
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/// clusters available. </returns>
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internal abstract bool GrowChain(BlockIndex! index,
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int requestedExtensionLength,
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out int actualExtensionLength);
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/// <summary> Truncates chain past specified new tail
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/// cluster. </summary>
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internal abstract void TruncateChain(BlockIndex! index,
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int lengthInClusters);
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/// <summary> Populates BlockIndex with clusters from chain.
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/// </summary>
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internal abstract void PopulateIndex(BlockIndex! index,
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int firstCluster);
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/// <summary> Property for clean shutdown bit held in FAT.
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/// <para> This property has no physical meaning on FAT12. </para>
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///</summary>
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internal abstract bool CleanShutdown { get; set; }
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/// <summary> Property for hard error bit held in FAT.
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/// <para> This property has no physical meaning on FAT12. </para>
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///</summary>
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internal abstract bool HardError { get; set; }
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/// <summary> Value representing total number of clusters. </summary>
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internal abstract int TotalClusters { get; }
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/// <summary> Value representing end of cluster chain. </summary>
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internal abstract int EndOfChain { get; }
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/// <summary> Value representing of bad cluster. </summary>
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internal abstract int BadCluster { get; }
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}
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}
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