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Use unsigned atom sizes and counts #12

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Merged
snowskeleton merged 1 commit into from
Jun 1, 2026
+6 −5
Merged

Use unsigned atom sizes and counts #12

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11 changes: 6 additions & 5 deletions src/snowcrypt/snowcrypt.py
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@


fshort, fint, flong = (">h", 2), (">i", 4), (">q", 8)
fuint, fulong = (">I", 4), (">Q", 8)


class Translator:
Expand All @@ -31,8 +32,8 @@ def next(self, format: tuple):
return data

def readAtomSize(self, inStream: BufferedReader) -> int:
atomLength = self.readOne(fint, inStream)
return atomLength if atomLength != 1 else self.readOne(flong, inStream)
atomLength = self.readOne(fuint, inStream)
return atomLength if atomLength != 1 else self.readOne(fulong, inStream)

def readOne(self, format: tuple, inStream: BufferedReader):
length = format[1]
Expand All @@ -49,7 +50,7 @@ def write(self, out: BufferedWriter) -> int:

def _decrypt_aavd(inStream: BufferedReader, key, iv, t: Translator):
# setup
length = t.next(fint)
length = t.next(fuint)
aes = newAES(key, MODE_CBC, iv=iv)

# for cipher padding, (up to) last 2 bytes are unencrypted
Expand Down Expand Up @@ -134,8 +135,8 @@ def mdat(
t.readOne(fint, inStream)
t.readOne(fint, inStream)
t.readOne(fint, inStream)
sum_block_length = t.readOne(fint, inStream)
block_count = t.readOne(fint, inStream)
sum_block_length = t.readOne(fuint, inStream)
block_count = t.readOne(fuint, inStream)

# next come the atom specific fields
# aavd has a list of sample sizes and then the samples.
Expand Down
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