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>

4 files changed, 104 insertions, 0 deletions

diff --git a/tests/micropython/ringio.py b/tests/micropython/ringio.py
new file mode 100644
index 000000000..45774bc2e
--- /dev/null
+++ b/tests/micropython/ringio.py
@@ -0,0 +1,48 @@
+# Check that micropython.RingIO works correctly.
+
+import micropython
+
+try:
+    micropython.RingIO
+except AttributeError:
+    print("SKIP")
+    raise SystemExit
+
+rb = micropython.RingIO(16)
+print(rb)
+
+print(rb.any())
+
+rb.write(b"\x00")
+print(rb.any())
+
+rb.write(b"\x00")
+print(rb.any())
+
+print(rb.read(2))
+print(rb.any())
+
+
+rb.write(b"\x00\x01")
+print(rb.read())
+
+print(rb.read(1))
+
+# Try to write more data than can fit at one go.
+print(rb.write(b"\x00\x01" * 10))
+print(rb.write(b"\x00"))
+print(rb.read())
+
+
+ba = bytearray(17)
+rb = micropython.RingIO(ba)
+print(rb)
+print(rb.write(b"\x00\x01" * 10))
+print(rb.write(b"\x00"))
+print(rb.read())
+
+try:
+    # Size must be int.
+    micropython.RingIO(None)
+except TypeError as ex:
+    print(ex)
diff --git a/tests/micropython/ringio.py.exp b/tests/micropython/ringio.py.exp
new file mode 100644
index 000000000..b27ea472c
--- /dev/null
+++ b/tests/micropython/ringio.py.exp
@@ -0,0 +1,16 @@
+<RingIO>
+0
+1
+2
+b'\x00\x00'
+0
+b'\x00\x01'
+b''
+16
+0
+b'\x00\x01\x00\x01\x00\x01\x00\x01\x00\x01\x00\x01\x00\x01\x00\x01'
+<RingIO>
+16
+0
+b'\x00\x01\x00\x01\x00\x01\x00\x01\x00\x01\x00\x01\x00\x01\x00\x01'
+can't convert NoneType to int
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())
diff --git a/tests/micropython/ringio_async.py.exp b/tests/micropython/ringio_async.py.exp
new file mode 100644
index 000000000..dfeb71d89
--- /dev/null
+++ b/tests/micropython/ringio_async.py.exp
@@ -0,0 +1,4 @@
+w 120
+b'ABC123ABC123ABC123ABC123ABC123ABC123ABC123ABC123ABC123ABC123ABC123ABC123ABC123ABC123ABC123ABC123ABC123ABC123ABC123ABC123'
+r 120
+True