Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Base / MS / Internal / IO / Zip / ZipIOExtraFieldPaddingElement.cs / 1305600 / ZipIOExtraFieldPaddingElement.cs
//------------------------------------------------------------------------------ //------------- *** WARNING *** //------------- This file is part of a legally monitored development project. //------------- Do not check in changes to this project. Do not raid bugs on this //------------- code in the main PS database. Do not contact the owner of this //------------- code directly. Contact the legal team at �ZSLegal� for assistance. //------------- *** WARNING *** //----------------------------------------------------------------------------- //----------------------------------------------------------------------------- // //// Copyright (C) Microsoft Corporation. All rights reserved. // // // Description: // This is an internal class that is used to implement parsing and editing of a padding extra field // structure. This extra field is used to optimize the performance dealing with Zip64 extra field. // When we need to create Zip64 extra field the extra padding bytes are used to create such // structure so that the subsequent bytes don't have to be moved. // // History: // 03/23/2006: [....]: Added support for Padding Extra Field // //----------------------------------------------------------------------------- using System; using System.Diagnostics; using System.IO; using System.Windows; namespace MS.Internal.IO.Zip { ////// This class is used to represent and parse the Padding Extra Field /// /// The Padding Extra Field is defined as: /// Header ID UInt16 (2 bytes) 0xA220 /// Length of the field UInt16 (2 bytes) /// Signature UInt16 (2 bytes) 0xA028 (for verification) /// Padding Initial Value UInt16 (2 bytes) Padding size originally requested by the caller /// Padding ? bytes Padding respresented by null characters /// internal class ZipIOExtraFieldPaddingElement : ZipIOExtraFieldElement { // creates a brand new empty Padding extra field element internal static ZipIOExtraFieldPaddingElement CreateNew() { ZipIOExtraFieldPaddingElement newElement = new ZipIOExtraFieldPaddingElement(); return newElement; } // parse Padding extra field element internal override void ParseDataField(BinaryReader reader, UInt16 size) { // The signature is already read and validated Debug.Assert(size >= MinimumSize); // It is guaranteed that there is enough bytes to read in UInt16 // since it is already checked from ZipIOExtraFieldElement.Parse() _initialRequestedPaddingSize = reader.ReadUInt16(); // need to subtract the size of the signature and size fields // We don't need to use checked{} since size is guaranteed to be bigger than // MinimumFieldDataSize by the called (ZipIOExtraFieldElement.Parse) size -= _minimumFieldDataSize; _paddingSize = size; // Skip the padding if (_paddingSize != 0) { reader.BaseStream.Seek(size, SeekOrigin.Current); } } internal static bool MatchesPaddingSignature(byte[] sniffiedBytes) { if (sniffiedBytes.Length < _signatureSize) { return false; } Debug.Assert(sniffiedBytes.Length == _signatureSize); if (BitConverter.ToUInt16(sniffiedBytes, 0) != _signature) { return false; } return true; } internal override void Save(BinaryWriter writer) { writer.Write(_constantFieldId); writer.Write(SizeField); writer.Write(_signature); writer.Write(_initialRequestedPaddingSize); for (int i = 0; i < _paddingSize; ++i) { writer.Write((byte) 0); } } // This property calculates size of the field on disk (how many bytes need to be allocated on the disk) // id + size field + data field (SizeField) internal override UInt16 Size { get { return checked((UInt16) (SizeField + MinimumSize)); } } // This property calculates the value of the size record whch holds the size without the Id and without the size itself. // we are always guranteed that Size == SizeField + 2 * sizeof(UInt16)) internal override UInt16 SizeField { get { return checked((UInt16) (_minimumFieldDataSize + _paddingSize)); } } static internal UInt16 ConstantFieldId { get { return _constantFieldId; } } static internal UInt16 MinimumFieldDataSize { get { return _minimumFieldDataSize; } } static internal UInt16 SignatureSize { get { return _signatureSize; } } internal UInt16 PaddingSize { get { return _paddingSize; } set { _paddingSize = value; } } //------------------------------------------------------ // // Private Constructor // //----------------------------------------------------- internal ZipIOExtraFieldPaddingElement() : base(_constantFieldId) { _initialRequestedPaddingSize = _newInitialPaddingSize; _paddingSize = _initialRequestedPaddingSize; } //------------------------------------------------------ // // Private Methods // //------------------------------------------------------ //----------------------------------------------------- // // Private fields // //------------------------------------------------------ private const UInt16 _constantFieldId = 0xA220; private const UInt16 _signature = 0xA028; // 20 is the maximum size of Zip64 Extra Field element we can use for Local File Header // (Id, Size, Compressed and UnCompressed Sizes; 2 + 2 + 8 + 8 = 20) // DiskNumber and Relative Offset of Local File Header is not counted since we don't use // it in Local File Header private const UInt16 _newInitialPaddingSize = 20; // UInt16 signature // UInt16 initial requested padding size private static readonly UInt16 _minimumFieldDataSize = 2 * sizeof(UInt16); private static readonly UInt16 _signatureSize = sizeof(UInt16); private UInt16 _paddingSize; private UInt16 _initialRequestedPaddingSize; } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007. // Copyright (c) Microsoft Corporation. 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