From 11d279a1b60cff60c3be150bb8dd1213d8b3946b Mon Sep 17 00:00:00 2001
From: Ryan Summers <ryan.summers@vertigo-designs.com>
Date: Mon, 26 Jul 2021 13:07:07 +0200
Subject: [PATCH] StreamFormat -> Into<u8>

---
 scripts/stream_throughput.py | 150 +++++++++++++----------------------
 src/net/data_stream.rs       |  16 ++--
 src/net/mod.rs               |   5 +-
 3 files changed, 68 insertions(+), 103 deletions(-)

diff --git a/scripts/stream_throughput.py b/scripts/stream_throughput.py
index 5d6aa16..94bcf66 100644
--- a/scripts/stream_throughput.py
+++ b/scripts/stream_throughput.py
@@ -14,19 +14,50 @@ import logging
 # Representation of a single data batch transmitted by Stabilizer.
 Packet = collections.namedtuple('Packet', ['index', 'data'])
 
-# Specifies a known format for incoming packets.
-#
-# * `sample_size_bytes` is the number of bytes required for each sample in the batch.
-# * `batch_format` is a `struct` format string that will be provided the `batch_size` as an named
-# argument. This format string will be used to deserialize each batch of data from the frame.
-Format = collections.namedtuple('Format', ['sample_size_bytes', 'batch_format'])
+# The magic header half-word at the start of each packet.
+MAGIC_HEADER = 0x057B
+
+# The struct format of the header.
+HEADER_FORMAT = '<HBBI'
 
 # All supported formats by this reception script.
+#
+# The items in this dict are functions that will be provided the sampel batch size and will return
+# the struct deserialization code to unpack a single batch.
 FORMAT = {
-    0: Format(sample_size_bytes=8,
-              batch_format='<{batch_size}H{batch_size}H{batch_size}H{batch_size}H')
+    1: lambda batch_size: f'<{batch_size}H{batch_size}H{batch_size}H{batch_size}H'
 }
 
+def parse_packet(buf):
+    """ Attempt to parse packets from the received buffer. """
+    # Attempt to parse a block from the buffer.
+    if len(buf) < struct.calcsize(HEADER_FORMAT):
+        return None
+
+    # Parse out the packet header
+    magic, format_id, batch_size, sequence_number = struct.unpack_from(HEADER_FORMAT, buf)
+    buf = buf[struct.calcsize(HEADER_FORMAT):]
+
+    if magic != MAGIC_HEADER:
+        logging.warning('Encountered bad magic header: %s', hex(magic))
+        return None
+
+    if format_id not in FORMAT:
+        raise Exception(f'Unknown format specifier: {format_id}')
+
+    frame_format = FORMAT[format_id](batch_size)
+
+    batch_count = len(buf) / struct.calcsize(frame_format)
+
+    packets = []
+    for offset in range(batch_count):
+        data = struct.unpack_from(frame_format, buf)
+        buf = buf[struct.calcsize(frame_format):]
+        packets.append(Packet(sequence_number + offset, data))
+
+    return packets
+
+
 class Timer:
     """ A basic timer for measuring elapsed time periods. """
 
@@ -66,78 +97,13 @@ class Timer:
         return now - self.start_time
 
 
-class PacketParser:
-    """ Utilize class used for parsing received UDP data. """
+def sequence_delta(previous_sequence, next_sequence):
+    """ Check the number of items between two sequence numbers. """
+    if previous_sequence is None:
+        return 0
 
-    def __init__(self):
-        """ Initialize the parser. """
-        self.buf = b''
-        self.total_bytes = 0
-
-
-    def ingress(self, data):
-        """ Ingress received UDP data. """
-        self.total_bytes += len(data)
-        self.buf += data
-
-
-    def parse_all_packets(self):
-        """ Parse all received packets from the receive buffer.
-
-        Returns:
-            A list of received Packets.
-        """
-        packets = []
-        while True:
-            new_packets = self._parse()
-            if new_packets:
-                packets += new_packets
-            else:
-                return packets
-
-
-    def _parse(self):
-        """ Attempt to parse packets from the received buffer. """
-        # Attempt to parse a block from the buffer.
-        if len(self.buf) < 7:
-            return None
-
-        # Parse out the packet header
-        start_id, format_id, batch_count, batch_size = struct.unpack_from('<HHHB', self.buf)
-
-        if format_id not in FORMAT:
-            raise Exception(f'Unknown format specifier: {format_id}')
-
-        frame_format = FORMAT[format_id]
-        required_length = 7 + batch_count * frame_format.sample_size_bytes * batch_size
-
-        if len(self.buf) < required_length:
-            return None
-
-        self.buf = self.buf[7:]
-
-        packets = []
-        for offset in range(batch_count):
-            format_string = frame_format.batch_format.format(batch_size=batch_size)
-            data = struct.unpack_from(format_string, self.buf)
-            self.buf = self.buf[struct.calcsize(format_string):]
-            packets.append(Packet(start_id + offset, data))
-
-        return packets
-
-
-def check_index(previous_index, next_index):
-    """ Check if two indices are sequential. """
-    if previous_index == -1:
-        return True
-
-    # Handle index roll-over. Indices are only stored in 16-bit numbers.
-    if next_index < previous_index:
-        next_index += 65536
-
-    expected_index = previous_index + 1
-
-    return next_index == expected_index
+    delta = next_sequence - (previous_sequence + 1)
+    return delta & 0xFFFFFFFF
 
 
 def main():
@@ -153,48 +119,40 @@ def main():
     logging.basicConfig(level=logging.INFO,
                         format='%(asctime)s.%(msecs)03d %(levelname)-8s %(message)s')
 
-    last_index = -1
+    last_index = None
 
     drop_count = 0
     good_blocks = 0
+    total_bytes = 0
 
     timer = Timer()
-    parser = PacketParser()
 
     while True:
         # Receive any data over UDP and parse it.
-        data = connection.recv(4096)
+        data = connection.recv(1024)
         if data and not timer.is_started():
             timer.start()
 
-        parser.ingress(data)
-
         # Handle any received packets.
-        for packet in parser.parse_all_packets():
+        total_bytes += len(data)
+        packet = parse_packet(data)
 
+        if packet:
             # Handle any dropped packets.
-            if not check_index(last_index, packet.index):
-                print(f'Drop from {hex(last_index)} to {hex(packet.index)}')
-                if packet.index < (last_index + 1):
-                    dropped = packet.index + 65536 - (last_index + 1)
-                else:
-                    dropped = packet.index - (last_index + 1)
-
-                drop_count += dropped
-
+            drop_count += sequence_delta(last_index, packet.index)
             last_index = packet.index
             good_blocks += 1
 
         # Report the throughput periodically.
         if timer.is_triggered():
-            drate = parser.total_bytes * 8 / 1e6 / timer.elapsed()
+            drate = total_bytes * 8 / 1e6 / timer.elapsed()
 
             print(f'''
 Data Rate:       {drate:.3f} Mbps
 Received Blocks: {good_blocks}
 Dropped blocks:  {drop_count}
 
-Metadata: {parser.total_bytes / 1e6:.3f} MB in {timer.elapsed():.2f} s
+Metadata: {total_bytes / 1e6:.3f} MB in {timer.elapsed():.2f} s
 ----
 ''')
             timer.arm()
diff --git a/src/net/data_stream.rs b/src/net/data_stream.rs
index b86410b..8560b29 100644
--- a/src/net/data_stream.rs
+++ b/src/net/data_stream.rs
@@ -89,6 +89,12 @@ pub enum StreamFormat {
     AdcDacData = 1,
 }
 
+impl From<StreamFormat> for u8 {
+    fn from(format: StreamFormat) -> u8 {
+        format as u8
+    }
+}
+
 impl From<StreamTarget> for SocketAddr {
     fn from(target: StreamTarget) -> SocketAddr {
         SocketAddr::new(
@@ -184,7 +190,7 @@ pub struct FrameGenerator {
     pool: &'static Pool<[u8; FRAME_SIZE]>,
     current_frame: Option<StreamFrame>,
     sequence_number: u32,
-    format: StreamFormat,
+    format: u8,
 }
 
 impl FrameGenerator {
@@ -195,7 +201,7 @@ impl FrameGenerator {
         Self {
             queue,
             pool,
-            format: StreamFormat::Unknown,
+            format: StreamFormat::Unknown.into(),
             current_frame: None,
             sequence_number: 0,
         }
@@ -209,10 +215,8 @@ impl FrameGenerator {
     /// # Args
     /// * `format` - The desired format of the stream.
     #[doc(hidden)]
-    pub(crate) fn set_format(&mut self, format: StreamFormat) {
-        assert!(self.format == StreamFormat::Unknown);
-        assert!(format != StreamFormat::Unknown);
-        self.format = format;
+    pub(crate) fn set_format(&mut self, format: impl Into<u8>) {
+        self.format = format.into();
     }
 
     /// Add a batch to the current stream frame.
diff --git a/src/net/mod.rs b/src/net/mod.rs
index fe0a7e9..ca1bb3d 100644
--- a/src/net/mod.rs
+++ b/src/net/mod.rs
@@ -113,9 +113,12 @@ where
     }
 
     /// Enable live data streaming.
+    ///
+    /// # Args
+    /// * `format` - A unique u8 code indicating the format of the data.
     pub fn enable_streaming(
         &mut self,
-        format: data_stream::StreamFormat,
+        format: impl Into<u8>,
     ) -> FrameGenerator {
         let mut generator = self.generator.take().unwrap();
         generator.set_format(format);