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[TupleVariation] Use bytearray() instead of io.Bytes()

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This commit is contained in:
Behdad Esfahbod 2021-04-07 15:03:12 -06:00
parent 869f00507b
commit 9405244617
1 changed files with 20 additions and 16 deletions
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36
Lib/fontTools/ttLib/tables/TupleVariation.py
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@ -310,11 +310,14 @@ class TupleVariation(object):
deltaX.append(c) deltaX.append(c)
elif c is not None: elif c is not None:
raise TypeError("invalid type of delta: %s" % type(c)) raise TypeError("invalid type of delta: %s" % type(c))
return self.compileDeltaValues_(deltaX) + self.compileDeltaValues_(deltaY) bytearr = bytearray()
self.compileDeltaValues_(deltaX, bytearr)
self.compileDeltaValues_(deltaY, bytearr)
return bytearr
@staticmethod @staticmethod
def compileDeltaValues_(deltas): def compileDeltaValues_(deltas, bytearr=None):
"""[value1, value2, value3, ...] --> bytestring """[value1, value2, value3, ...] --> bytearray
Emits a sequence of runs. Each run starts with a Emits a sequence of runs. Each run starts with a
byte-sized header whose 6 least significant bits byte-sized header whose 6 least significant bits
@ -329,20 +332,21 @@ class TupleVariation(object):
bytes; if (header & 0x40) is set, the delta values are bytes; if (header & 0x40) is set, the delta values are
signed 16-bit integers. signed 16-bit integers.
""" # Explaining the format because the 'gvar' spec is hard to understand. """ # Explaining the format because the 'gvar' spec is hard to understand.
stream = io.BytesIO() if bytearr is None:
bytearr = bytearray()
pos = 0 pos = 0
while pos < len(deltas): while pos < len(deltas):
value = deltas[pos] value = deltas[pos]
if value == 0: if value == 0:
pos = TupleVariation.encodeDeltaRunAsZeroes_(deltas, pos, stream) pos = TupleVariation.encodeDeltaRunAsZeroes_(deltas, pos, bytearr)
elif value >= -128 and value <= 127: elif value >= -128 and value <= 127:
pos = TupleVariation.encodeDeltaRunAsBytes_(deltas, pos, stream) pos = TupleVariation.encodeDeltaRunAsBytes_(deltas, pos, bytearr)
else: else:
pos = TupleVariation.encodeDeltaRunAsWords_(deltas, pos, stream) pos = TupleVariation.encodeDeltaRunAsWords_(deltas, pos, bytearr)
return stream.getvalue() return bytearr
@staticmethod @staticmethod
def encodeDeltaRunAsZeroes_(deltas, offset, stream): def encodeDeltaRunAsZeroes_(deltas, offset, bytearr):
runLength = 0 runLength = 0
pos = offset pos = offset
numDeltas = len(deltas) numDeltas = len(deltas)
@ -350,11 +354,11 @@ class TupleVariation(object):
pos += 1 pos += 1
runLength += 1 runLength += 1
assert runLength >= 1 and runLength <= 64 assert runLength >= 1 and runLength <= 64
stream.write(bytechr(DELTAS_ARE_ZERO | (runLength - 1))) bytearr.append(DELTAS_ARE_ZERO | (runLength - 1))
return pos return pos
@staticmethod @staticmethod
def encodeDeltaRunAsBytes_(deltas, offset, stream): def encodeDeltaRunAsBytes_(deltas, offset, bytearr):
runLength = 0 runLength = 0
pos = offset pos = offset
numDeltas = len(deltas) numDeltas = len(deltas)
@ -375,13 +379,13 @@ class TupleVariation(object):
pos += 1 pos += 1
runLength += 1 runLength += 1
assert runLength >= 1 and runLength <= 64 assert runLength >= 1 and runLength <= 64
stream.write(bytechr(runLength - 1)) bytearr.append(runLength - 1)
for i in range(offset, pos): for i in range(offset, pos):
stream.write(struct.pack('b', otRound(deltas[i]))) bytearr.extend(struct.pack('b', otRound(deltas[i])))
return pos return pos
@staticmethod @staticmethod
def encodeDeltaRunAsWords_(deltas, offset, stream): def encodeDeltaRunAsWords_(deltas, offset, bytearr):
runLength = 0 runLength = 0
pos = offset pos = offset
numDeltas = len(deltas) numDeltas = len(deltas)
@ -409,9 +413,9 @@ class TupleVariation(object):
pos += 1 pos += 1
runLength += 1 runLength += 1
assert runLength >= 1 and runLength <= 64 assert runLength >= 1 and runLength <= 64
stream.write(bytechr(DELTAS_ARE_WORDS | (runLength - 1))) bytearr.append(DELTAS_ARE_WORDS | (runLength - 1))
for i in range(offset, pos): for i in range(offset, pos):
stream.write(struct.pack('>h', otRound(deltas[i]))) bytearr.extend(struct.pack('>h', otRound(deltas[i])))
return pos return pos
@staticmethod @staticmethod