/// <summary>
/// <para>
/// Traverses a contiguous sequence of JPEG2000 boxes.
/// Visits recursively the contiguous sequence of boxes of
/// every superbox.
/// </para>
/// </summary>
/// <param name="stream"></param>
/// <param name="boxLimit"></param>
/// <returns>
/// An ordered collection representing the sequence
/// of boxes that appear in the underlying IO stream
/// </returns>
public static IEnumerable <Jp2Box> TraverseBoxes(Stream stream, long boxLimit)
{
List <Jp2Box> boxes = new List <Jp2Box>();
long bytesLeft = boxLimit;
while (bytesLeft > 0)
{
Jp2Box box = Jp2Box.Open(stream, bytesLeft);
bytesLeft -= box.Length;
boxes.Add(box);
}
return(boxes);
}
/// <summary>
/// <para>
/// Parses a JPEG2000 box from the underlying IO stream.
/// </para>
/// <para>
/// Stream must be positioned at the start of the box
/// </para>
/// <para>
/// Advances the stream to the first byte of the box content
/// </para>
/// </summary>
/// <param name="stream">the underlying IO stream</param>
/// <param name="boxLimit">
/// number of bytes that are left to be read in the box container
/// </param>
/// <returns></returns>
public static Jp2Box Open(Stream stream, long boxLimit)
{
if (boxLimit < MIN_BOX_LENGTH)
{
throw new ArgumentException(
"Not enough data left to parse JPEG2000 box");
}
long length = stream.ReadUInt32();
if (length == 0)
{
// ISO 15443-1, Annex I section 4 Box Definition
// If the value of this field is 0, then the length of the
// box was not known when the LBox field was written. In this
// case, this box contains all bytes up to the end of the file.
length = boxLimit;
}
else if (length > USE_EXTENDED_LENGTH && length < MIN_BOX_LENGTH)
{
// these values are supposedly reserved for ISO use..
throw new ArgumentException(
"JPEG2000 box length cannot be determined");
}
uint ucode = stream.ReadUInt32();
uint dataOffset = 8;
if (length == USE_EXTENDED_LENGTH)
{
if (boxLimit < (MIN_BOX_LENGTH + 8))
{
throw new ArgumentException(
"not enough data to read extended length field");
}
ulong ulLength = stream.ReadUInt64();
if (ulLength > long.MaxValue)
{
throw new ArgumentOutOfRangeException(
"box is larger than 2^63 bytes");
}
length = (long)ulLength;
dataOffset += 8;
}
if (length > boxLimit)
{
throw new ArgumentException(
"Box length is larger than the limit on box container");
}
if (Jp2Box.IsSuperbox(ucode))
{
var boxes = TraverseBoxes(stream, length - dataOffset);
return(new Jp2Box(ucode, length, dataOffset, boxes));
}
else
{
// advance the stream position beyond the content of this box.
// TraverseBoxes recursive call relies on Open call to
// advance the stream position.
stream.Seek(length - dataOffset, SeekOrigin.Current);
return(new Jp2Box(ucode, length, dataOffset));
}
}
