trx_toolkit/data_msg.py: use list comprehension for bit conversion

This approach is much better than buf.append() in terms of performance.
Consider the following bit conversion benchmark code:

  usbits = [random.randint(0, 254) for i in range(GSM_BURST_LEN)]
  ubits = [int(b > 128) for b in usbits]

  for i in range(100000):
      sbits = DATAMSG.usbit2sbit(usbits)
      assert(DATAMSG.sbit2usbit(sbits) == usbits)

      sbits = DATAMSG.ubit2sbit(ubits)
      assert(DATAMSG.sbit2ubit(sbits) == ubits)

=== Before this patch:

 59603795 function calls (59603761 primitive calls) in 11.357 seconds

   Ordered by: internal time

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
 59200093    3.389    0.000    3.389    0.000 {method 'append' of 'list' objects}
   100000    2.212    0.000    3.062    0.000 data_msg.py:191(usbit2sbit)
   100000    1.920    0.000    2.762    0.000 data_msg.py:214(sbit2ubit)
   100000    1.835    0.000    2.677    0.000 data_msg.py:204(sbit2usbit)
   100000    1.760    0.000    2.613    0.000 data_msg.py:224(ubit2sbit)

=== After this patch:

  803794 function calls (803760 primitive calls) in 3.547 seconds

   Ordered by: internal time

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
   100000    1.284    0.000    1.284    0.000 data_msg.py:203(<listcomp>)
   100000    0.864    0.000    0.864    0.000 data_msg.py:193(<listcomp>)
   100000    0.523    0.000    0.523    0.000 data_msg.py:198(<listcomp>)
   100000    0.500    0.000    0.500    0.000 data_msg.py:208(<listcomp>)
        1    0.237    0.237    3.547    3.547 data_msg.py:25(<module>)
   100000    0.035    0.000    0.899    0.000 data_msg.py:191(usbit2sbit)
   100000    0.035    0.000    0.558    0.000 data_msg.py:196(sbit2usbit)
   100000    0.033    0.000    0.533    0.000 data_msg.py:206(ubit2sbit)
   100000    0.033    0.000    1.317    0.000 data_msg.py:201(sbit2ubit)

So the new implementation is ~70% faster in this case, and takes
significantly less function calls according to cProfile [1].

[1] https://docs.python.org/3.8/library/profile.html

Change-Id: I01c07160064c8107e5db7d913ac6dec6fc419945

1 files changed, 6 insertions, 37 deletions

diff --git a/src/target/trx_toolkit/data_msg.py b/src/target/trx_toolkit/data_msg.py
index 8710702b..35e09d68 100644
--- a/src/target/trx_toolkit/data_msg.py
+++ b/src/target/trx_toolkit/data_msg.py
@@ -190,45 +190,22 @@ class DATAMSG:
 	# Converts unsigned soft-bits {254..0} to soft-bits {-127..127}
 	@staticmethod
 	def usbit2sbit(bits):
-		buf = []
-
-		for bit in bits:
-			if bit == 0xff:
-				buf.append(-127)
-			else:
-				buf.append(127 - bit)
-
-		return buf
+		return [-127 if (b == 0xff) else 127 - b for b in bits]
 
 	# Converts soft-bits {-127..127} to unsigned soft-bits {254..0}
 	@staticmethod
 	def sbit2usbit(bits):
-		buf = []
-
-		for bit in bits:
-			buf.append(127 - bit)
-
-		return buf
+		return [127 - b for b in bits]
 
 	# Converts soft-bits {-127..127} to bits {1..0}
 	@staticmethod
 	def sbit2ubit(bits):
-		buf = []
-
-		for bit in bits:
-			buf.append(1 if bit < 0 else 0)
-
-		return buf
+		return [int(b < 0) for b in bits]
 
 	# Converts bits {1..0} to soft-bits {-127..127}
 	@staticmethod
 	def ubit2sbit(bits):
-		buf = []
-
-		for bit in bits:
-			buf.append(-127 if bit else 127)
-
-		return buf
+		return [-127 if b else 127 for b in bits]
 
 	# Validates the message fields (throws ValueError)
 	def validate(self):
@@ -426,11 +403,7 @@ class DATAMSG_L12TRX(DATAMSG):
 
 	# Generate a random message specific burst
 	def rand_burst(self, length = GSM_BURST_LEN):
-		self.burst = []
-
-		for i in range(length):
-			ubit = random.randint(0, 1)
-			self.burst.append(ubit)
+		self.burst = [random.randint(0, 1) for i in range(length)]
 
 	# Transforms this message to TRX2L1 message
 	def gen_trx2l1(self, ver = None):
@@ -836,14 +809,10 @@ class DATAMSG_TRX2L1(DATAMSG):
 
 	# Generate a random message specific burst
 	def rand_burst(self, length = None):
-		self.burst = []
-
 		if length is None:
 			length = self.mod_type.bl
 
-		for i in range(length):
-			sbit = random.randint(-127, 127)
-			self.burst.append(sbit)
+		self.burst = [random.randint(-127, 127) for i in range(length)]
 
 	# Transforms this message to L12TRX message
 	def gen_l12trx(self, ver = None):