public AtomCallbackArgs(uint type, long size, Stream stream, long startPosition, SequentialStreamReader reader)
{
Type = type;
Size = size;
Stream = stream;
StartPosition = startPosition;
Reader = reader;
}
/// <summary>
/// Reads atom data from <paramref name="stream"/>, invoking <paramref name="handler"/> for each atom encountered.
/// </summary>
/// <param name="stream">The stream to read atoms from.</param>
/// <param name="handler">A callback function to handle each atom.</param>
/// <param name="stopByBytes">The maximum number of bytes to process before discontinuing.</param>
public static void ProcessAtoms([NotNull] Stream stream, [NotNull] Action<AtomCallbackArgs> handler, long stopByBytes = -1)
{
var reader = new SequentialStreamReader(stream);
var seriesStartPos = stream.Position;
while (stopByBytes == -1 || stream.Position < seriesStartPos + stopByBytes)
{
var atomStartPos = stream.Position;
// Length of the atom's data, in bytes, including size bytes
long atomSize;
try
{
atomSize = reader.GetUInt32();
}
catch (IOException)
{
// TODO don't use exception to trap end of stream
return;
}
// Typically four ASCII characters, but may be non-printable.
// By convention, lowercase 4CCs are reserved by Apple.
var atomType = reader.GetUInt32();
if (atomSize == 1)
{
// Size doesn't fit in 32 bits so read the 64 bit size here
// TODO GetUInt64 (i.e. unsigned)
atomSize = reader.GetInt64();
}
else
{
Debug.Assert(atomSize >= 8, "Atom should be at least 8 bytes long");
}
var args = new AtomCallbackArgs(atomType, atomSize, stream, atomStartPos, reader);
handler(args);
if (args.Cancel)
return;
if (atomSize == 0)
return;
var toSkip = atomStartPos + atomSize - stream.Position;
if (toSkip < 0)
throw new Exception("Handler moved stream beyond end of atom");
reader.TrySkip(toSkip);
}
}