py/objringio: Add micropython.RingIO() interface for general use.

This commit adds a new `RingIO` type which exposes the internal ring-buffer
code for general use in Python programs.  It has the stream interface
making it similar to `StringIO` and `BytesIO`, except `RingIO` has a fixed
buffer size and is automatically safe when reads and writes are in
different threads or an IRQ.

This new type is enabled at the "extra features" ROM level.

Signed-off-by: Andrew Leech <andrew.leech@planetinnovation.com.au>

1 files changed, 36 insertions, 0 deletions

diff --git a/tests/micropython/ringio_async.py b/tests/micropython/ringio_async.py
new file mode 100644
index 000000000..2a4befc35
--- /dev/null
+++ b/tests/micropython/ringio_async.py
@@ -0,0 +1,36 @@
+# Check that micropython.RingIO works correctly with asyncio.Stream.
+
+import micropython
+
+try:
+    import asyncio
+
+    asyncio.StreamWriter
+    micropython.RingIO
+except (AttributeError, ImportError):
+    print("SKIP")
+    raise SystemExit
+
+rb = micropython.RingIO(16)
+rba = asyncio.StreamWriter(rb)
+
+data = b"ABC123" * 20
+print("w", len(data))
+
+
+async def data_writer():
+    global data
+    rba.write(data)
+    await rba.drain()
+
+
+async def main():
+    task = asyncio.create_task(data_writer())
+    await asyncio.sleep_ms(10)
+    read = await rba.readexactly(len(data))
+    print(read)
+    print("r", len(read))
+    print(read == data)
+
+
+asyncio.run(main())