/// <summary>
/// Write the EMBL (and all its data/content) to a file.
/// </summary>
/// <param name="file">A <see cref="File"/> representing the file to write to.</param>
/// <param name="position">The byte-position in the file to write the EBML to.</param>
/// <param name="reserved">The reserved size in bytes that the EBML may overwrite from the given position. (Default: 0, insert)</param>
public void Write(File file, long position, long reserved = 0)
{
if (file == null)
{
throw new ArgumentNullException(nameof(file));
}
if (position > file.Length || position < 0)
{
throw new ArgumentOutOfRangeException(nameof(position));
}
if (Data != null && Children != null)
{
throw new UnsupportedFormatException("EBML element cannot contain both Data and Children");
}
// Reserve required size upfront to speed up writing
var size = Size;
if (size > reserved)
{
// Extend reserved size
file.Insert(size - reserved, position + reserved);
reserved = size;
}
// Write the Header
var header = Header;
file.Insert(header, position, header.Count);
position += header.Count;
reserved -= header.Count;
// Write the data/content
if (Data != null)
{
file.Insert(Data, position, Data.Count);
}
else if (Children != null)
{
foreach (var child in Children)
{
child.Write(file, position, reserved);
var csize = child.Size;
position += csize;
reserved -= csize;
}
}
}
/// <summary>
/// Write the <see cref="DataSize"/> to the EBML file.
/// Resize the data-size length to 8 bytes.
/// This will *not* insert extra bytes, but overwrite next contiguous bytes.
/// It will claim the size added on the value of the data-size.
/// </summary>
/// <returns>Offset created in Writing the new data-size</returns>
public long WriteDataSize()
{
ulong value = DataSize;
const ulong newsize_length = 8;
// Figure out the ID size in bytes
ulong mask = 0xFF000000, id_length = 4;
while (id_length > 0 && (ebml_id & mask) == 0)
{
id_length--;
mask >>= 8;
}
if (id_length == 0)
{
throw new CorruptFileException("invalid EBML ID (zero)");
}
// Figure out the Data size length in bytes
ulong size_length = DataOffset - offset - id_length;
if (size_length > 8)
{
throw new CorruptFileException("invalid EBML element size");
}
// Construct the data-size field
ByteVector vector = new ByteVector((int)newsize_length);
mask = value;
for (int i = (int)newsize_length - 1; i >= 0; i--)
{
vector[i] = (byte)(mask & 0xFF);
mask >>= 8;
}
// Set the marker bit
vector[0] |= 0x100 >> (int)newsize_length;
// Write data-size field to file
file.Insert(vector, (long)(offset + id_length), (long)newsize_length);
// Update fields
ulong woffset = newsize_length - size_length;
DataOffset += woffset;
DataSize = value - woffset;
return((long)woffset);
}
