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98 lines
3.7 KiB
C#
98 lines
3.7 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Runtime.InteropServices;
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using System.Text;
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using System.Threading.Tasks;
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namespace SCJMapper_V2.p4kFile
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{
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/// <summary>
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/// Represents an EndOfCentralDirRecord entry in the p4k file
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/// The file seems to be based on a Zip64 file structure
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/// </summary>
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internal class p4kEndOfCentralDirRecord
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{
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/// <summary>
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/// ctor: Create class from data returned by the Reader
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/// </summary>
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/// <param name="reader">A binary data reader for this type of data - positioned at last page</param>
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public p4kEndOfCentralDirRecord( p4kRecReader reader )
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{
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// sanity check only
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System.Diagnostics.Trace.Assert( Marshal.SizeOf( typeof( MyRecord ) ) == RecordLength,
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"Record size does not match!(" + Marshal.SizeOf( typeof( MyRecord ) ).ToString( ) + ")" );
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if ( reader.IsOpen( ) ) {
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try {
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long thisPos = 0;
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// 20180804BM- fix when the last page is barely used and the sig is one or more pages before
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// - backup one or more pages to find end of dir (max 10 times)
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int tries = 10;
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while ( !m_itemValid && ( tries > 0 ) ) {
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thisPos = reader.Position;
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long cPos = p4kSignatures.FindSignatureInPage( reader, p4kSignatures.EndOfCentralDirRecord );
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if ( cPos >= 0 ) {
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m_recordOffset = cPos;
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reader.Seek( cPos );
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m_item = p4kRecReader.ByteToType<MyRecord>( reader.TheReader );
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m_itemValid = true;
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}
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else {
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// backup one page again
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reader.Seek( thisPos );
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reader.BackwardPage( );
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tries--;
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}
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}
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}
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catch {
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m_itemValid = false;
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m_recordOffset = -1;
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}
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finally {
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if ( !m_itemValid ) {
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throw new OperationCanceledException( string.Format( "EOF - cannot find EndOfCentralDirRecord" ) );
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}
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}
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}
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}
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public bool IsValid { get => m_itemValid; }
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public long RecordOffset { get => m_recordOffset; }
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private MyRecord m_item;
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private bool m_itemValid = false;
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private long m_recordOffset = -1; // offset from start (current position)
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//4.3.16 End of central directory record:
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private const int RecordLength = 22;
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[StructLayout( LayoutKind.Sequential, Pack = 1 )] // , Size = RecordLength
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private struct MyRecord
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{
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[MarshalAs( UnmanagedType.ByValArray, SizeConst = 4 )]
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public byte[] ID; // end of central dir signature 4 bytes(0x06054b50)
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[MarshalAs( UnmanagedType.U2 )]
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public UInt16 DiskNumber; // number of this disk 2 bytes
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[MarshalAs( UnmanagedType.U2 )]
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public UInt16 DiskNumbersFromStart; // number of the disk with the start of the central directory 2 bytes
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[MarshalAs( UnmanagedType.U2 )]
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public UInt16 NumEntriesOnDisk; // total number of entries in the central directory on this disk 2 bytes
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[MarshalAs( UnmanagedType.U2 )]
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public UInt16 TotalNumEntries; // total number of entries in the central directory 2 bytes
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[MarshalAs( UnmanagedType.U4 )]
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public UInt32 SizeOfCDir; // size of the central directory 4 bytes
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[MarshalAs( UnmanagedType.U4 )]
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public UInt32 OffsetOfCDir; // offset of start of central directory with respect to the starting disk number 4 bytes
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[MarshalAs( UnmanagedType.U2 )]
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public UInt16 CommentLen; // .ZIP file comment length 2 bytes
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// .ZIP file comment( variable size )
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}
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}
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}
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