Setting up vertex attributes with OpenTK - opengl

Question

I am having trouble setting the position, normal, and texture coordinate attributes in my shader. I am using meshomatic to load obj files, here is how the attributes are added to a single vbo:
void LoadBuffers(MeshData m)
{
float[] verts, norms, texcoords;
uint[] indices;
m.OpenGLArrays(out verts, out norms, out texcoords, out indices);
GL.GenBuffers(1, out dataBuffer);
GL.GenBuffers(1, out indexBuffer);
// Set up data for VBO.
// We're going to use one VBO for all geometry, and stick it in
// in (VVVVNNNNCCCC) order. Non interleaved.
int buffersize = (verts.Length + norms.Length + texcoords.Length);
float[] bufferdata = new float[buffersize];
vertOffset = 0;
normOffset = verts.Length;
texcoordOffset = (verts.Length + norms.Length);
verts.CopyTo(bufferdata, vertOffset);
norms.CopyTo(bufferdata, normOffset);
texcoords.CopyTo(bufferdata, texcoordOffset);
bool v = false;
for (int i = texcoordOffset; i < bufferdata.Length; i++)
{
if (v)
{
bufferdata[i] = 1 - bufferdata[i];
v = false;
}
else
{
v = true;
}
}
// Load geometry data
GL.BindBuffer(BufferTarget.ArrayBuffer, dataBuffer);
GL.BufferData<float>(BufferTarget.ArrayBuffer, (IntPtr)(buffersize * sizeof(float)), bufferdata,
BufferUsageHint.StaticDraw);
// Load index data
GL.BindBuffer(BufferTarget.ElementArrayBuffer, indexBuffer);
GL.BufferData<uint>(BufferTarget.ElementArrayBuffer,
(IntPtr)(indices.Length * sizeof(uint)), indices, BufferUsageHint.StaticDraw);
}
And here is how I am drawing:
void DrawBuffer()
{
// Push current Array Buffer state so we can restore it later
GL.PushClientAttrib(ClientAttribMask.ClientVertexArrayBit);
GL.ClientActiveTexture(TextureUnit.Texture0);
GL.BindTexture(TextureTarget.Texture2D, diff);
GL.EnableVertexAttribArray(positionIndex);
GL.BindBuffer(BufferTarget.ArrayBuffer, dataBuffer);
GL.VertexAttribPointer(positionIndex, 3, VertexAttribPointerType.Float, false, 0, vertOffset);
GL.EnableVertexAttribArray(texcoordIndex);
GL.BindBuffer(BufferTarget.ArrayBuffer, dataBuffer);
GL.VertexAttribPointer(texcoordIndex, 2, VertexAttribPointerType.Float, false, 0, texcoordOffset);
GL.EnableVertexAttribArray(normalIndex);
GL.BindBuffer(BufferTarget.ArrayBuffer, dataBuffer);
GL.VertexAttribPointer(normalIndex, 3, VertexAttribPointerType.Float, false, 0, normOffset);
// Index array
GL.BindBuffer(BufferTarget.ElementArrayBuffer, indexBuffer);
GL.DrawElements(PrimitiveType.Triangles, m.Tris.Length * 3, DrawElementsType.UnsignedInt, IntPtr.Zero);
// Restore the state
GL.PopClientAttrib();
}
However my texture coordinates are wrong. It seems that only a single pixel from my texture is used to cover the entire obj. I think I am using GL.VertexAttribPointer(...) incorrectly. What is the second arg int "size"?