feat(stream_reader): optimize serial stream protocol detection. reduce CPU busy-spins
This commit is contained in:
jack
@@ -32,9 +32,35 @@ class StreamReader:
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self._thread = threading.Thread(target=self._run, daemon = True)
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self._thread.start()
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def _read_chunk(self, min_bytes: int = 1) -> bytes:
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"""Read a chunk of available bytes from the transport.
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Reads up to 256 bytes in one shot instead of byte-at-a-time,
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falling back to single-byte reads with a yield when nothing is
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immediately available."""
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chunk = self._transport.read(max(min_bytes, 256))
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if chunk:
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return chunk
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# Nothing available right now – yield briefly to avoid busy-spin.
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b = self._transport.read(1)
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if not b:
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time.sleep(0.005)
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return b
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def _accumulate(self, needed: int) -> bytearray:
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"""Accumulate *needed* bytes using buffered reads."""
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buf = bytearray()
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while len(buf) < needed and not self._stop.is_set():
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chunk = self._transport.read(needed - len(buf))
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if not chunk:
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time.sleep(0.005)
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continue
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buf.extend(chunk)
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return buf
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def _run(self) -> None:
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try:
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# Check the first few bytes to determine if the wafer is streaming binary, ASCII hex dump, or text lines.
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# Peek at the first few bytes to determine protocol.
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peek_buf = bytearray()
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while not self._stop.is_set() and len(peek_buf) < 32:
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b = self._transport.read(1)
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@@ -47,16 +73,24 @@ class StreamReader:
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if self._stop.is_set() or not peek_buf:
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return
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detect_buf = bytes(c for c in peek_buf if c not in (10, 13, 0))
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if not detect_buf:
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detect_buf = bytes(peek_buf)
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raw = bytes(peek_buf)
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if detect_buf.startswith(b"\xaa\x88") or (len(detect_buf) >= 2 and detect_buf[0] == 0xAA and detect_buf[1] == 0x88):
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self._run_binary(bytes(peek_buf))
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elif b"," in detect_buf:
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self._run_text_lines(bytes(peek_buf))
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else:
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self._run_ascii(bytes(peek_buf))
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# Binary sync bytes are the strongest signal.
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if raw.startswith(b"\xaa\x88"):
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self._run_binary(raw)
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return
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# Text-lines (CSV) requires BOTH a newline AND commas in the
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# pre-newline content. This avoids misclassifying a binary
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# payload that happens to contain 0x2C as text.
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has_newline = b"\n" in raw or b"\r" in raw
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line_before_nl = raw.split(b"\n")[0].split(b"\r")[0]
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if has_newline and b"," in line_before_nl:
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self._run_text_lines(raw)
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return
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# Default: ASCII hex dump stream.
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self._run_ascii(raw)
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finally:
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try:
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self._transport.close()
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@@ -68,6 +102,7 @@ class StreamReader:
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buf = bytearray(initial_bytes)
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while not self._stop.is_set():
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# Find sync marker in buffer.
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idx = 0
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synced = False
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while idx < len(buf) - 1:
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@@ -78,10 +113,10 @@ class StreamReader:
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if synced:
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buf = buf[idx:]
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# Accumulate header (5 bytes after sync).
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while len(buf) < 7 and not self._stop.is_set():
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b = self._transport.read(1)
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if b:
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buf.extend(b)
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chunk = self._read_chunk()
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buf.extend(chunk)
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if self._stop.is_set():
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return
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@@ -89,10 +124,11 @@ class StreamReader:
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payload_len = int.from_bytes(buf[5:7], byteorder='little')
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total_packet_len = 2 + 5 + payload_len + 2
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while len(buf) < total_packet_len and not self._stop.is_set():
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b = self._transport.read(1)
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if b:
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buf.extend(b)
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# Accumulate the rest of the packet in one buffered read.
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remaining = total_packet_len - len(buf)
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if remaining > 0:
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extra = self._accumulate(remaining)
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buf.extend(extra)
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if self._stop.is_set():
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return
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@@ -112,14 +148,14 @@ class StreamReader:
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buf = buf[total_packet_len:]
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else:
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# Resync: keep only trailing 0xAA if present, then read more.
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if len(buf) > 0 and buf[-1] == 0xAA:
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buf = bytearray([0xAA])
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else:
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buf.clear()
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b = self._transport.read(1)
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if b:
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buf.extend(b)
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chunk = self._read_chunk()
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buf.extend(chunk)
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def _run_ascii(self, initial_bytes: bytes) -> None:
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log.info("StreamReader: starting ASCII hex dump stream parsing")
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@@ -127,6 +163,7 @@ class StreamReader:
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valid_words = 80 if self._family_code == "X" else 244
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block_words = 256
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word_char_len = 4
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chars_needed = block_words * word_char_len # total hex chars per block
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hex_chars = bytearray()
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if initial_bytes:
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@@ -136,44 +173,43 @@ class StreamReader:
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elif b == 0xAA:
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hex_chars.append(b)
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def read_next_hex_char() -> str | None:
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if hex_chars:
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val = chr(hex_chars.pop(0))
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return val
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while not self._stop.is_set():
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b = self._transport.read(1)
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if not b:
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continue
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if b[0] == 0xAA:
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hex_chars.extend(b)
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return None
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c = chr(b[0])
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if c in "0123456789ABCDEFabcdef":
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return c
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return None
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seq = 0
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while not self._stop.is_set():
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word_buffer = []
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eof = False
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for _ in range(block_words):
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word_str = ""
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for _ in range(word_char_len):
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c = read_next_hex_char()
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if c is None:
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eof = True
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# Accumulate a full block of hex characters using buffered reads.
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while len(hex_chars) < chars_needed and not self._stop.is_set():
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chunk = self._read_chunk(min_bytes=chars_needed - len(hex_chars))
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for byte in chunk:
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if byte == 0xAA:
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# Sync marker appeared – hand off to binary parser.
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hex_chars.append(byte)
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break
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word_str += c
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if eof or len(word_str) < word_char_len:
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eof = True
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break
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word_buffer.append(word_str)
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c = chr(byte)
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if c in "0123456789ABCDEFabcdef":
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hex_chars.append(c)
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else:
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continue
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break # broke out of inner loop due to 0xAA
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if eof:
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if hex_chars and hex_chars[0] == 0xAA:
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log.info("StreamReader: Detected 0xAA, switching to binary mode.")
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self._run_binary(bytes(hex_chars))
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# Check for early termination (0xAA sync marker anywhere in buffer).
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aa_idx = hex_chars.find(bytes([0xAA]))
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if aa_idx >= 0:
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log.info("StreamReader: Detected 0xAA at position %d, switching to binary mode.", aa_idx)
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self._run_binary(hex_chars[aa_idx:])
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return
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# Parse words from the accumulated hex characters.
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word_buffer = []
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for i in range(0, min(len(hex_chars), chars_needed), word_char_len):
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word_str = hex_chars[i:i + word_char_len]
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if len(word_str) < word_char_len:
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break
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word_buffer.append(bytes(word_str))
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if not word_buffer:
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time.sleep(0.01)
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continue
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hex_chars = hex_chars[len(word_buffer) * word_char_len:]
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valid_hex_words = word_buffer[:valid_words]
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values = []
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@@ -198,7 +234,8 @@ class StreamReader:
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seq = 0
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while not self._stop.is_set():
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if b"\n" in buf:
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# Drain complete lines from the buffer.
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while b"\n" in buf:
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line_bytes, _, buf = buf.partition(b"\n")
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line = line_bytes.decode('utf-8', errors='ignore').strip()
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if line:
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@@ -210,13 +247,10 @@ class StreamReader:
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except Exception as exc:
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self.error_count += 1
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self._on_error(exc)
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continue
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b = self._transport.read(1)
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if not b:
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time.sleep(0.005)
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continue
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buf.extend(b)
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# Read more data using buffered reads.
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chunk = self._read_chunk()
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buf.extend(chunk)
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def stop(self) -> None:
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self._stop.set()
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