| import contextlib |
| import inspect |
|
|
| class MyBuffer: |
| def __init__(self, data: bytes): |
| self.data = bytearray(data) |
| self.view = None |
|
|
| def __buffer__(self, flags: int) -> memoryview: |
| if flags != inspect.BufferFlags.FULL_RO: |
| raise TypeError("Only BufferFlags.FULL_RO supported") |
| if self.view is not None: |
| raise RuntimeError("Buffer already held") |
| self.view = memoryview(self.data) |
| return self.view |
|
|
| def __release_buffer__(self, view: memoryview) -> None: |
| assert self.view is view |
| self.view.release() |
| self.view = None |
|
|
| def extend(self, b: bytes) -> None: |
| if self.view is not None: |
| raise RuntimeError("Cannot extend held buffer") |
| self.data.extend(b) |
|
|
| buffer = MyBuffer(b"capybara") |
| with memoryview(buffer) as view: |
| view[0] = ord("C") |
|
|
| with contextlib.suppress(RuntimeError): |
| buffer.extend(b"!") |
|
|
| buffer.extend(b"!") |
|
|
| with memoryview(buffer) as view: |
| assert view.tobytes() == b"Capybara!" |
|
|
