//4.3.7 Local file header:
// local file header signature 4 bytes(0x04034b50)
// version needed to extract 2 bytes
// general purpose bit flag 2 bytes
// compression method 2 bytes
// last mod file time 2 bytes
// last mod file date 2 bytes
// crc-32 4 bytes
// compressed size 4 bytes
// uncompressed size 4 bytes
// file name length 2 bytes
// extra field length 2 bytes
// file name( variable size )
// extra field( variable size )
//4.3.8 File data
// Immediately following the local header for a file
// SHOULD be placed the compressed or stored data for the file.
// If the file is encrypted, the encryption header for the file
// SHOULD be placed after the local header and before the file
// data. The series of[local file header][encryption header]
// [file data][data descriptor] repeats for each file in the
// .ZIP archive.
// Zero-byte files, directories, and other file types that
// contain no content MUST not include file data.
// 4.5.3 -Zip64 Extended Information Extra Field(0x0001):
// The following is the layout of the zip64 extended
// information "extra" block.If one of the size or
// offset fields in the Local or Central directory
// record is too small to hold the required data,
// a Zip64 extended information record is created.
// The order of the fields in the zip64 extended
// information record is fixed, but the fields MUST
// only appear if the corresponding Local or Central
// directory record field is set to 0xFFFF or 0xFFFFFFFF.
// Note: all fields stored in Intel low - byte / high - byte order.
// Value Size Description
// ---- - ---------------
//(ZIP64)0x0001 2 bytes Tag for this "extra" block type
// Size 2 bytes Size of this "extra" block
// Original
// Size 8 bytes Original uncompressed file size
// Compressed
// Size 8 bytes Size of compressed data
// Relative Header
// Offset 8 bytes Offset of local header record
// Disk Start
// Number 4 bytes Number of the disk on which
// this file starts
// This entry in the Local header MUST include BOTH original
// and compressed file size fields.If encrypting the
// central directory and bit 13 of the general purpose bit
// flag is set indicating masking, the value stored in the
// Local Header for the original file size will be zero.
/// <summary>
/// ctor: Create class from data returned by the Reader
/// </summary>
/// <param name="reader">A binary data reader for this type of data</param>
public p4kFileHeader(p4kRecReader reader)
{
// sanity check only
System.Diagnostics.Trace.Assert(Marshal.SizeOf(typeof(MyRecord)) == RecordLength,
"Record size does not match!(" + Marshal.SizeOf(typeof(MyRecord)).ToString( ) + ")");
System.Diagnostics.Trace.Assert(Marshal.SizeOf(typeof(MyZ64ExtraRecord)) == Z64ExtraRecordLength,
"Extra Record size does not match!(" + Marshal.SizeOf(typeof(MyZ64ExtraRecord)).ToString( ) + ")");
if (reader.IsOpen( ))
{
try {
long cPos = reader.Position;
do
{
// Fileheaders are Page aligned - scan to find one
reader.AdvancePage( ); // to next page
cPos = reader.Position;
string cPosS = cPos.ToString("X");
m_recordOffset = cPos;
m_item = p4kRecReader.ByteToType <MyRecord>(reader.TheReader);
m_itemValid = m_item.ID.SequenceEqual(p4kSignatures.LocalFileHeaderCry);
} while ((cPos < reader.Length) && !m_itemValid);
// get some file attributes
if (m_itemValid)
{
if (m_item.FilenameLength > 0)
{
ReadFilename(reader);
}
if (m_item.ExtraFieldLength > 0)
{
ReadExtradata(reader); // Likely Zip64 extensions
}
m_fileDateTime = p4kFileTStamp.FromDos(m_item.LastModDate, m_item.LastModTime);
// check if standard fields or extension is used for size information
if (m_item.CompressedSize < 0xffffffff)
{
m_fileSizeComp = m_item.CompressedSize;
m_fileSizeUnComp = m_item.UncompressedSize;
}
else
{
m_fileSizeComp = (long)m_z64Item.CompressedSize;
m_fileSizeUnComp = (long)m_z64Item.UncompressedSize;
}
// now we would be able to read the file content
// but we skip it for now to process the next header
m_fileOffset = reader.TheReader.BaseStream.Position; // save position of this item
reader.TheReader.BaseStream.Seek(m_fileSizeComp, SeekOrigin.Current);
}
else
{
// actually invalid but good manner ..
m_recordOffset = -1;
m_fileOffset = -1;
m_fileSizeComp = 0;
m_fileSizeUnComp = 0;
}
}
catch {
m_itemValid = false;
}
finally {
if (!m_itemValid)
{
if (m_item.ID.SequenceEqual(p4kSignatures.CentralDirRecord))
{
// read beyond the file entries
throw new OperationCanceledException(string.Format("EOF - found Central Directory header {0}", m_item.ID.ToString( )));
}
else
{
// other error
throw new NotSupportedException(string.Format("Cannot process fileheader ID {0}", m_item.ID.ToString( )));
}
}
}
}
}
