public Page (File file, long position) : this (new PageHeader (file, position))
{
if (file == null)
throw new ArgumentNullException ("file");
file.Seek (position + header.Size);
foreach (int packet_size in header.PacketSizes)
packets.Add (file.ReadBlock (packet_size));
}
public File (File.IFileAbstraction abstraction,
ReadStyle propertiesStyle) : base (abstraction)
{
Mode = AccessMode.Read;
try {
tag = new GroupedComment ();
Read (propertiesStyle);
TagTypesOnDisk = TagTypes;
} finally {
Mode = AccessMode.Closed;
}
}
public PageHeader (File file, long position)
{
file.Seek (position);
// An Ogg page header is at least 27 bytes, so we'll go ahead and read that
// much and then get the rest when we're ready for it.
ByteVector data = file.ReadBlock (27);
if (data.Count < 27 || !data.StartsWith ("OggS"))
throw new CorruptFileException ("Error reading page header");
_version = data [4];
_flags = (PageFlags) data [5];
_absolute_granular_position = data.Mid( 6, 8).ToULong (false);
_stream_serial_number = data.Mid(14, 4).ToUInt (false);
_page_sequence_number = data.Mid(18, 4).ToUInt (false);
// Byte number 27 is the number of page segments, which is the only variable
// length portion of the page header. After reading the number of page
// segments we'll then read in the coresponding data for this count.
int page_segment_count = data [26];
ByteVector page_segments = file.ReadBlock (page_segment_count);
// Another sanity check.
if(page_segment_count < 1 || page_segments.Count != page_segment_count)
throw new CorruptFileException ("Incorrect number of page segments");
// The base size of an Ogg page 27 bytes plus the number of lacing values.
_size = (uint)(27 + page_segment_count);
_packet_sizes = new List<int> ();
int packet_size = 0;
_data_size = 0;
for (int i = 0; i < page_segment_count; i++)
{
_data_size += page_segments [i];
packet_size += page_segments [i];
if (page_segments [i] < 255)
{
_packet_sizes.Add (packet_size);
packet_size = 0;
}
}
if (packet_size > 0)
_packet_sizes.Add (packet_size);
}
public File (File.IFileAbstraction abstraction) : this (abstraction, ReadStyle.Average)
{}
public static void OverwriteSequenceNumbers (File file,
long position,
IDictionary<uint, int> shiftTable)
{
bool done = true;
foreach (KeyValuePair<uint, int> pair in shiftTable)
if (pair.Value != 0) {
done = false;
break;
}
if (done)
return;
while (position < file.Length) {
PageHeader header = new PageHeader (file, position);
int size = (int) (header.Size + header.DataSize);
if (shiftTable.ContainsKey (header.StreamSerialNumber)
&& shiftTable [header.StreamSerialNumber] != 0) {
file.Seek (position);
ByteVector page_data = file.ReadBlock (size);
ByteVector new_data = ByteVector.FromUInt (
(uint)(header.PageSequenceNumber +
shiftTable [header.StreamSerialNumber]),
false);
for (int i = 18; i < 22; i ++)
page_data [i] = new_data [i - 18];
for (int i = 22; i < 26; i++)
page_data [i] = 0;
new_data.Add (ByteVector.FromUInt (
page_data.Checksum, false));
file.Seek (position + 18);
file.WriteBlock (new_data);
}
position += size;
}
}
