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Fix returning too much data when grabbing a chunk that overlaps a patched section and the end of a file.

This commit is contained in:
Jennifer Taylor 2021-10-25 21:19:59 +00:00
parent 88e9d0406e
commit 1db7de771e
2 changed files with 21 additions and 7 deletions
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16
arcadeutils/filebytes.py
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@ -286,7 +286,7 @@ class FileBytes:
# Determine start of slice # Determine start of slice
if key.start is None: if key.start is None:
start = 0 if step > 0 else self.__patchlength start = 0 if step > 0 else (self.__patchlength - 1)
elif key.start < 0: elif key.start < 0:
start = self.__patchlength + key.start start = self.__patchlength + key.start
else: else:
@ -407,7 +407,7 @@ class FileBytes:
# Append any amount of data we need to read past the end of the file. # Append any amount of data we need to read past the end of the file.
if len(data) < stop - start: if len(data) < stop - start:
data.extend([0] * (stop - len(data))) data.extend([0] * ((stop - start) - len(data)))
else: else:
data = [0] * (stop - start) data = [0] * (stop - start)
@ -418,23 +418,25 @@ class FileBytes:
return bytes(data) return bytes(data)
elif start > stop and step == -1: elif start > stop and step == -1:
start += 1
stop += 1
if not modifications: if not modifications:
# This is just a continguous read, reversed # This is just a continguous read, reversed
self.__handle.seek(stop + 1) self.__handle.seek(stop)
return self.__handle.read(start - stop)[::-1] return self.__handle.read(start - stop)[::-1]
else: else:
if (stop + 1) < self.__filelength: if stop < self.__filelength:
self.__handle.seek(stop + 1) self.__handle.seek(stop)
data = [x for x in self.__handle.read(start - stop)] data = [x for x in self.__handle.read(start - stop)]
# Append any amount of data we need to read past the end of the file. # Append any amount of data we need to read past the end of the file.
if len(data) < start - stop: if len(data) < start - stop:
data.extend([0] * (start - len(data))) data.extend([0] * ((start - stop) - len(data)))
else: else:
data = [0] * (start - stop) data = [0] * (start - stop)
# Now we have to modify the data with our own overlay. # Now we have to modify the data with our own overlay.
for index, off in enumerate(range(stop + 1, start + 1)): for index, off in enumerate(range(stop, start)):
if off in self.__patches: if off in self.__patches:
data[index] = self.__patches[off] data[index] = self.__patches[off]

12
tests/test_FileBytes.py
View File

@ -298,6 +298,18 @@ class TestFileBytes(unittest.TestCase):
b, b,
) )
def test_read_after_append(self) -> None:
fb = FileBytes(io.BytesIO(b"0123456789"))
# Do some simple appending.
fb.append(b"abcdef")
# Now try to read over the boundary.
self.assertEqual(
fb[5:15],
b"56789abcde",
)
def test_modify_variants(self) -> None: def test_modify_variants(self) -> None:
fb = FileBytes(io.BytesIO(b"0123456789")) fb = FileBytes(io.BytesIO(b"0123456789"))