def read(self, size=-1, offset=0) -> bytes:
"""Read data from the buffer.
:param int size: The bytes to read. -1 means the entire buffer (default)
:param int offset: Byte read offset
:rtype: bytes
"""
if size == -1:
size = self._size
# Catch this before confusing INVALID_OPERATION is raised
if size < 1:
raise ValueError("Attempting to read 0 or less bytes from buffer")
# Manually detect this so it doesn't raise a confusing INVALID_VALUE error
if size + offset > self._size:
raise ValueError(
(
"Attempting to read outside the buffer. "
f"Buffer size: {self._size} "
f"Reading from {offset} to {size + offset}"
)
)
gl.glBindBuffer(gl.GL_ARRAY_BUFFER, self._glo)
ptr = gl.glMapBufferRange(gl.GL_ARRAY_BUFFER, offset, size, gl.GL_MAP_READ_BIT)
data = string_at(ptr, size=size)
gl.glUnmapBuffer(gl.GL_ARRAY_BUFFER)
return data
def _read(self, size):
""" Debug method to read data from the buffer. """
gl.glBindBuffer(gl.GL_ARRAY_BUFFER, self.buffer_id)
ptr = gl.glMapBufferRange(gl.GL_ARRAY_BUFFER, gl.GLintptr(0), size,
gl.GL_MAP_READ_BIT)
print(f"Reading back from buffer:\n{string_at(ptr, size=size)}")
gl.glUnmapBuffer(gl.GL_ARRAY_BUFFER)