/// <summary>
/// Turns the GLB data contained in a stream into a GLBObject. Will copy to the outStream if specified
/// </summary>
/// <param name="root">The glTF root to turn into a GLBObject</param>
/// <param name="inputGLBStream">The stream the glb came in</param>
/// <param name="outStream">If outstream is specified, the glb gets copied to it</param>
/// <param name="inputGLBStreamStartPosition">Offset into the buffer that the GLB starts</param>
/// <returns>A constructed GLBObject</returns>
public static GLBObject ConstructFromGLB(GLTFRoot root, Stream inputGLBStream, Stream outStream = null,
long inputGLBStreamStartPosition = 0)
{
if (outStream != null)
{
inputGLBStream.Position = inputGLBStreamStartPosition;
inputGLBStream.CopyTo(outStream);
}
else
{
outStream = inputGLBStream;
}
// header information is 4 bytes in, past the magic number
inputGLBStream.Position = 4 + inputGLBStreamStartPosition;
GLBHeader header = GLTFParser.ParseGLBHeader(inputGLBStream);
inputGLBStream.Position = GLTFParser.HEADER_SIZE + inputGLBStreamStartPosition;
List <ChunkInfo> allChunks = GLTFParser.FindChunks(inputGLBStream);
ChunkInfo jsonChunkInfo = new ChunkInfo
{
Type = ChunkFormat.JSON
};
ChunkInfo binaryChunkInfo = new ChunkInfo
{
Type = ChunkFormat.BIN
};
foreach (ChunkInfo chunkInfo in allChunks)
{
switch (chunkInfo.Type)
{
case ChunkFormat.JSON:
jsonChunkInfo = chunkInfo;
break;
case ChunkFormat.BIN:
binaryChunkInfo = chunkInfo;
break;
}
}
if (jsonChunkInfo.Length == 0)
{
throw new ArgumentException("JSON chunk must exists for valid GLB", nameof(inputGLBStream));
}
// todo: compute the initial bufferview list
return(new GLBObject
{
Root = root,
Stream = outStream,
StreamStartPosition = inputGLBStreamStartPosition,
Header = header,
JsonChunkInfo = jsonChunkInfo,
BinaryChunkInfo = binaryChunkInfo
});
}
private static void WriteChunkHeader(Stream stream, ChunkInfo chunkInfo)
{
stream.Position = chunkInfo.StartPosition;
byte[] lengthBytes = BitConverter.GetBytes(chunkInfo.Length);
byte[] typeBytes = BitConverter.GetBytes((uint)chunkInfo.Type);
stream.Write(lengthBytes, 0, lengthBytes.Length);
stream.Write(typeBytes, 0, lengthBytes.Length);
}
public static ChunkInfo ParseChunkInfo(Stream stream)
{
ChunkInfo chunkInfo = new ChunkInfo
{
StartPosition = stream.Position
};
chunkInfo.Length = GetUInt32(stream); // 12
chunkInfo.Type = (ChunkFormat)GetUInt32(stream); // 16
return(chunkInfo);
}
private static void ParseJsonChunk(Stream stream, long startPosition)
{
GLBHeader header = ParseGLBHeader(stream); // 4, 8
if (header.Version != 2)
{
throw new GLTFHeaderInvalidException("Unsupported glTF version");
}
;
if (header.FileLength != (stream.Length - startPosition))
{
throw new GLTFHeaderInvalidException("File length does not match header.");
}
ChunkInfo chunkInfo = ParseChunkInfo(stream);
if (chunkInfo.Type != ChunkFormat.JSON)
{
throw new GLTFHeaderInvalidException("First chunk must be of type JSON");
}
}
public static List <ChunkInfo> FindChunks(Stream stream, long startPosition = 0)
{
stream.Position = startPosition + 4; // start after magic number bytes (4 bytes past)
ParseGLBHeader(stream);
List <ChunkInfo> allChunks = new List <ChunkInfo>();
// we only need to search for top two chunks (the JSON and binary chunks are guarenteed to be the top two chunks)
// other chunks can be in the file but we do not care about them
for (int i = 0; i < 2; ++i)
{
if (stream.Position == stream.Length)
{
break;
}
ChunkInfo chunkInfo = ParseChunkInfo(stream);
allChunks.Add(chunkInfo);
stream.Position += chunkInfo.Length;
}
return(allChunks);
}
