/// <summary>
/// Read in offsets. Converting to Int32 because .NET Stream.Read method takes Int32s.
/// </summary>
/// <param name="stream"></param>
/// <param name="trailer"></param>
/// <returns></returns>
private static int[] ReadNodeOffsets(Stream stream, PListTrailer trailer)
{
// the bitconverter library we use only knows how to deal with integer offsets
if (trailer.NumObjects > int.MaxValue)
{
throw new PListFormatException($"Offset table contains too many entries: {trailer.NumObjects}.");
}
var converter = EndianBitConverter.BigEndian;
// position the stream at the start of the offset table
if (stream.Seek((long)trailer.OffsetTableOffset, SeekOrigin.Begin) != (long)trailer.OffsetTableOffset)
{
throw new PListFormatException("Invalid plist file: unable to seek to start of the offset table.");
}
var offsetSize = trailer.OffsetIntSize;
var buffer = new byte[offsetSize];
var nodeOffsets = new int[trailer.NumObjects];
for (ulong i = 0; i < trailer.NumObjects; i++)
{
if (stream.Read(buffer, 0, buffer.Length) != buffer.Length)
{
throw new PListFormatException($"Invalid plist file: unable to read value {i} in the offset table.");
}
nodeOffsets[i] = ReadNumber(buffer, converter);
}
return(nodeOffsets);
}
private static PListTrailer ReadTrailer(Stream stream)
{
// trailer is 32 bytes long, at the end of the file
var buffer = new byte[32];
stream.Seek(-32, SeekOrigin.End);
if (stream.Read(buffer, 0, buffer.Length) != buffer.Length)
{
throw new PListFormatException("Invalid plist file: unable to read trailer.");
}
// all data in a binary plist file is big-endian
var converter = EndianBitConverter.BigEndian;
var trailer = new PListTrailer
{
Unused = new byte[5],
SortVersionl = buffer[5],
OffsetIntSize = buffer[6],
ObjectRefSize = buffer[7],
NumObjects = converter.ToUInt64(buffer, 8),
TopObject = converter.ToUInt64(buffer, 16),
OffsetTableOffset = converter.ToUInt64(buffer, 24)
};
return(trailer);
}
