// todo: this needs reimplemented. There is no such thing as a binary chunk index, and the chunk may not be in 0, 1, 2 order
// Moves stream position to binary chunk location
public static ChunkInfo SeekToBinaryChunk(Stream stream, int binaryChunkIndex, long startPosition = 0)
{
stream.Position = startPosition + 4; // start after magic number chunk
GLBHeader header = ParseGLBHeader(stream);
uint chunkOffset = 12; // sizeof(GLBHeader) + magic number
uint chunkLength = 0;
for (int i = 0; i < binaryChunkIndex + 2; ++i)
{
chunkOffset += chunkLength;
stream.Position = chunkOffset;
chunkLength = GetUInt32(stream);
chunkOffset += 8; // to account for chunk length (4 bytes) and type (4 bytes)
}
// Load Binary Chunk
if (chunkOffset + chunkLength <= header.FileLength)
{
ChunkFormat chunkType = (ChunkFormat)GetUInt32(stream);
if (chunkType != ChunkFormat.BIN)
{
throw new GLTFHeaderInvalidException("Second chunk must be of type BIN if present");
}
return(new ChunkInfo
{
StartPosition = stream.Position - CHUNK_HEADER_SIZE,
Length = chunkLength,
Type = chunkType
});
}
throw new GLTFHeaderInvalidException("File length does not match chunk header.");
}
// Moves stream position to binary chunk location
public static void SeekToBinaryChunk(Stream stream, int binaryChunkIndex, long startPosition = 0)
{
stream.Position = startPosition + 4; // start after magic number chunk
GLBHeader header = ParseGLBHeader(stream);
uint chunkOffset = 12; // sizeof(GLBHeader) + magic number
uint chunkLength = 0;
for (int i = 0; i < binaryChunkIndex + 2; ++i)
{
chunkOffset += chunkLength;
//vona 5/25/21
//stream.Position = chunkOffset;
stream.Position = startPosition + chunkOffset;
chunkLength = GetUInt32(stream);
chunkOffset += 8; // to account for chunk length (4 bytes) and type (4 bytes)
}
// Load Binary Chunk
if (chunkOffset + chunkLength <= header.FileLength)
{
uint chunkType = GetUInt32(stream);
if (chunkType != (uint)ChunkFormat.BIN)
{
throw new GLTFHeaderInvalidException("Second chunk must be of type BIN if present");
}
}
else
{
throw new GLTFHeaderInvalidException("File length does not match chunk header.");
}
}
// todo optimize: this can have a caching system where GLTFRoot stores data about JSON offset of a GLB
public static void ExtractBinaryChunk(byte[] gltfBinary, int binaryChunkIndex, out byte[] glbBuffer)
{
GLBHeader header = ParseGLBHeader(gltfBinary);
int chunkOffset = 12; // sizeof(GLBHeader) + magic number
int chunkLength = 0;
for (int i = 0; i < binaryChunkIndex + 2; ++i)
{
chunkOffset += chunkLength;
chunkLength = (int)GetChunkLength(gltfBinary, chunkOffset);
chunkOffset += 8; // to account for chunk length (4 bytes) and type (4 bytes)
}
// Load Binary Chunk
if (chunkOffset + chunkLength <= header.FileLength)
{
uint chunkType = BitConverter.ToUInt32(gltfBinary, chunkOffset - 4);
if (chunkType != (uint)ChunkFormat.BIN)
{
throw new GLTFHeaderInvalidException("Second chunk must be of type BIN if present");
}
glbBuffer = new byte[chunkLength];
System.Buffer.BlockCopy(gltfBinary, chunkOffset, glbBuffer, 0, chunkLength);
}
else
{
throw new GLTFHeaderInvalidException("File length does not match chunk header.");
}
}
private static string ParseJsonChunk(byte[] gltfBinary)
{
GLBHeader header = ParseGLBHeader(gltfBinary);
if (header.Version != 2)
{
throw new GLTFHeaderInvalidException("Unsupported glTF version");
}
;
if (header.FileLength != gltfBinary.Length)
{
throw new GLTFHeaderInvalidException("File length does not match header.");
}
uint chunkLength = GetChunkLength(gltfBinary, 12);
var chunkType = BitConverter.ToUInt32(gltfBinary, 16);
if (chunkType != (uint)ChunkFormat.JSON)
{
throw new GLTFHeaderInvalidException("First chunk must be of type JSON");
}
// Load JSON chunk
return(System.Text.Encoding.UTF8.GetString(gltfBinary, 20, (int)chunkLength));
}
/// <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 WriteHeader(Stream stream, GLBHeader header, long streamStartPosition)
{
stream.Position = streamStartPosition;
byte[] magicNumber = BitConverter.GetBytes(GLTFParser.MAGIC_NUMBER);
byte[] version = BitConverter.GetBytes(header.Version);
byte[] length = BitConverter.GetBytes(header.FileLength);
stream.Write(magicNumber, 0, magicNumber.Length);
stream.Write(version, 0, version.Length);
stream.Write(length, 0, length.Length);
}
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");
}
}
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.");
}
int chunkLength = (int)GetUInt32(stream); // 12
var chunkType = GetUInt32(stream); // 16
if (chunkType != (uint)ChunkFormat.JSON)
{
throw new GLTFHeaderInvalidException("First chunk must be of type JSON");
}
}
