RingIO is limited to 64kB
Description
Discussion: https://github.com/micropython/micropython/pull/9458#issuecomment-2581252345
Currently RingIO is limited to creating ring buffers of 64kB by the use of the following uint16_t variables in ringbuf.h:
typedef struct _ringbuf_t {
uint8_t *buf;
uint16_t size;
uint16_t iget;
uint16_t iput;
} ringbuf_t;
The suggestion is to change these to uint32_t to allow for >64kB ringbuffers. This would only be useful in ports with more than 64kB of heap available, so it may be worthwhile having different versions for different ports.
Or maybe the extra 6 bytes is acceptable across all ports for the sake of simplicity/consistency?
I note that other structures (like bytearray) don't have a 64kB limit, so this would seem to be some sort of precedent for changing the limit.
Code Size
This change would add 6 bytes to RAM usage whenever RingIO is invoked
Implementation
I hope the MicroPython maintainers or community will implement this feature
Code of Conduct
Yes, I agree
ringbuf: Zero-length ringbuf creation allowed, causes crash
Port, board and/or hardware
unix port, coverage variant, x86_64 linux
MicroPython version
MicroPython v1.26.0-preview.524.g255d74b5a8 on 2025-08-06; linux [GCC 12.2.0] version
Reproduction
Run the following script:
import micropython
rb = micropython.RingIO(bytearray(0))
rb.write(b'\1')
Expected behaviour
An exception is thown on line 2, because a zero-byte ring buffer is nonsense.
Observed behaviour
Division by zero (reported by Linux as SIGFPE) occurs on line 3:
>>> micropython.RingIO(bytearray(0)).write(b'\1')
Program received signal SIGFPE, Arithmetic exception.
0x0000555555605f33 in ringbuf_free (r=0x7ffff7c318a8) at ../../py/ringbuf.h:86
86 return (r->size + r->iget - r->iput - 1) % r->size;
Additional Information
Found via fuzzing, manually minimized.
Code of Conduct
Yes, I agree