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Fix some decomp logic

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Fixed some decomp logic, especially around writing out bits
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This commit is contained in:
Morgan Kelley
2025-09-16 09:37:28 -06:00
committed by GitHub
parent 3ac0cefe19
commit 0d403225a4
1 changed files with 44 additions and 19 deletions
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45
main.py
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@@ -11,7 +11,7 @@ class BZZCompressor:
with open(input_file_path, "rb") as input_file:
data.fromfile(input_file)
except IOError:
print("Could not open input file ...")
print("Could not open input file...")
raise
if len(data) > 9:
@@ -104,31 +104,56 @@ class BZZCompressor:
distance_data = data[0:16]
del data[0:16]
length = len_table[
# length here is the length of the data we are copying.
# We multiply by 8 since we are working with bits instead of bytes
length = (
len_table[
int(
(
distance_data
& bitarray(bin(int(len_mask.to01(), 2))[2:].zfill(16))
& bitarray(
bin(int(len_mask.to01(), 2))[2:].zfill(16)
)
).to01(),
2,
)
]
* 8
)
displacement = distance_data >> int(len_bits.to01(), 2)
# Displacement is how far back in the existing output_buffer we are
# looking to copy from. We multiply by 8 since we are working with bits and not bytes
displacement = (
int((distance_data >> int(len_bits.to01(), 2)).to01(), 2) * 8
)
if displacement == 0:
print("Error processing file. Displacement was 0")
# This shouldn't happen
if displacement <= 0:
print(
"Error processing file. Displacement was less than or equal to 0"
)
return
print(f"Output Buffer Size: {len(output_buffer)}")
print(f"Output Buffer Size (in bits): {len(output_buffer)}")
print(f"Distance Data: {distance_data.tobytes()}")
print(f"Displacement: {int(displacement.to01(), 2)}")
print(f"Displacement (in bits): {int(displacement.to01(), 2)}")
print(f"Length: {length}")
# Here we copy bit by bit from earlier in the output buffer.
# we use this instead of index slicing since the slice could lead to
# data we are currently copying into the buffer
for i in range(length):
output_buffer.append(
output_buffer[-int(displacement.to01(), 2)]
out_index = len(output_buffer)
copy_index = out_index - int(displacement.to01(), 2)
# This shouldn't happen
if copy_index < 0:
print(
"Error decompressing file. copy_index is out of range"
)
return
output_buffer.append(output_buffer[copy_index])
num_flags = bitarray(bin(int(num_flags.to01(), 2) - 1)[2:].zfill(24))