Reopen stdout as an unbuffered binary stream

We want to dump output directly from the device without any further
processing, to support binary data dumps; we also disable buffering
on stdout, to support piping output to other processes more cleanly.

itm-decode.py

@@ -6,12 +6,34 @@
 import sys
 import serial
 
-def printf(str, *args):
-    print(str % args, end='')
-
 color_lookup = { "red": 31, "green": 32, "cyan": 36, "yellow": 33 }
 def color(name, text):
-    return "\033[%dm%s\033[0m" % (color_lookup[name], text);
+    return b"\033[%dm%s\033[0m" % (color_lookup[name], text)
+
+stdout = None
+
+def printf(str, *args):
+    stdout.write(str.encode('utf-8') % args)
+
+def printf_color(name, str, *args):
+    stdout.write(color(name, str.encode('utf-8') % args))
+
+def sprintf_color(name, str, *args):
+    return color(name, str.encode('utf-8') % args)
+
+try:
+    # On Unix systems, print an additional marker in the output stream
+    # when SIGUSR1 or SIGUSR2 is received.  This is just to help clarify
+    # output when the chip is externally reset, etc.
+    import signal
+    def sigusr1_handler(signum, frame):
+        printf_color("yellow", "--- mark ---\n")
+    def sigusr2_handler(signum, frame):
+        printf_color("yellow", "--- reset ---\n")
+    signal.signal(signal.SIGUSR1, sigusr1_handler)
+    signal.signal(signal.SIGUSR2, sigusr2_handler)
+except AttributeError as e:
+    pass
 
 class ResyncException(Exception):
     pass
@@ -65,12 +87,13 @@ class ITMParser:
                     try:
                         text = self.parse(c)
                         if text:
-                            print(text)
+                            printf("%s\n", text)
                     except TimeoutException as e:
                         # Timeout inside a parser should be reported.
-                        print(color("red", "Timeout"))
+                        printf_color("red", "Timeout\n")
+                        break
             except ResyncException as e:
-                print(color("red", "Resync"))
+                printf_color("red", "Resync\n")
 
     def next(self):
         return next(self.synced_stream)
@@ -85,7 +108,7 @@ class ITMParser:
             return None # part of sync packet
 
         if c == 0x70:
-            return color("yellow", "overflow")
+            return sprintf_color("yellow", "overflow")
 
         if c & 0x0f == 0x00 and c & 0x70 != 0x00:
             return self.parse_timestamp(c)
@@ -94,7 +117,7 @@ class ITMParser:
             return self.parse_extension(c)
 
         if c & 0x0f == 0x04:
-            return color("yellow", "reserved %02x" % c)
+            return sprintf_color("yellow", "reserved %02x", c)
 
         if c & 0x04 == 0x00 and c & 0x03 != 0:
             return self.parse_sw(c)
@@ -102,7 +125,7 @@ class ITMParser:
         if c & 0x04 == 0x04 and c & 0x03 != 0:
             return self.parse_hw(c)
 
-        return color("red", "unknown %02x" % c)
+        return sprintf_color("red", "unknown %02x", c)
 
     def parse_sw(self, c):
         """
@@ -114,29 +137,29 @@ class ITMParser:
         for i in range(length):
             payload |= self.next() << (i * 8)
         if port == 0 and length == 1:
-            # Dump directly to stdout
-            print(chr(payload), end='')
+            # Dump directly to stdout as binary data
+            stdout.write(bytes([payload]))
             return None
-        msg = "SWIT port %d payload %0*x" % (port, 2 * length, payload)
-        return color('cyan', msg)
+        return sprintf_color('cyan', "SWIT port %d payload %0*x",
+                             port, 2 * length, payload)
 
     def parse_hw(self, c):
         """
         Parse HWIT packet
         """
-        return color("red", "TODO hw %02x" % c)
+        return sprintf_color("red", "TODO hw %02x", c)
 
     def parse_timestamp(self, c):
         """
         Parse timestamp packet
         """
-        return color("red", "TODO timestamp %02x" % c)
+        return sprintf_color("red", "TODO timestamp %02x", c)
 
     def parse_extension(self, c):
         """
         Parse extension packet
         """
-        return color("red", "TODO extension %02x" % c)
+        return sprintf_color("red", "TODO extension %02x", c)
 
 def main(argv):
     import argparse
@@ -152,16 +175,40 @@ def main(argv):
                         help="Serial port for SWO input")
     args = parser.parse_args()
 
+    # TODO: add option to backslash-escape output
+    # TODO: add option to disable color in output
+    # TODO: add option to control output buffering
+    import os
+    global stdout
+    stdout = os.fdopen(sys.stdout.fileno(), 'wb', 0)
+
     ser = serial.Serial(args.device, args.baudrate)
-    ser.timeout = 1
+
+    printf_color('green', 'ready\n')
 
     def input_stream():
         while True:
+            # Read one byte with a 1s timeout.
+            ser.timeout = 1
             data = ser.read(1)
             if len(data) == 0:
+                # Timeout
                 yield None
-            else:
-                yield data[0]
+                continue
+            yield data[0]
+
+            # Then read as many more as there are immediately
+            # available, and send them.  This is more efficient than
+            # reading each individual byte, when they're coming in
+            # fast.  Once they stop, we'll go back to the normal
+            # 1 byte read with timeout.
+            ser.timeout = 0
+            while True:
+                data = ser.read(65536)
+                if len(data) == 0:
+                    break
+                for c in data:
+                    yield c
 
     try:
         ITMParser(input_stream()).process()