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Use field size in AppendingTiffWriter

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This commit is contained in:
Andrew Murray 2024-09-20 22:31:00 +10:00
parent 3f24276bf2
commit 0a99d63028
1 changed files with 41 additions and 28 deletions
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69
src/PIL/TiffImagePlugin.py
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@ -2121,13 +2121,24 @@ class AppendingTiffWriter(io.BytesIO):
def write(self, data: Buffer, /) -> int:
return self.f.write(data)
def readShort(self) -> int:
(value,) = struct.unpack(self.shortFmt, self.f.read(2))
def _fmt(self, field_size: int) -> str:
try:
return {2: "H", 4: "L"}[field_size]
except KeyError:
msg = "offset is not supported"
raise RuntimeError(msg)
def _read(self, field_size: int) -> int:
(value,) = struct.unpack(
self.endian + self._fmt(field_size), self.f.read(field_size)
)
return value
def readShort(self) -> int:
return self._read(2)
def readLong(self) -> int:
(value,) = struct.unpack(self.longFmt, self.f.read(4))
return value
return self._read(4)
@staticmethod
def _verify_bytes_written(bytes_written: int | None, expected: int) -> None:
@ -2140,15 +2151,18 @@ class AppendingTiffWriter(io.BytesIO):
bytes_written = self.f.write(struct.pack(self.longFmt, value))
self._verify_bytes_written(bytes_written, 4)
def _rewriteLast(self, value: int, field_size: int) -> None:
self.f.seek(-field_size, os.SEEK_CUR)
bytes_written = self.f.write(
struct.pack(self.endian + self._fmt(field_size), value)
)
self._verify_bytes_written(bytes_written, field_size)
def rewriteLastShort(self, value: int) -> None:
self.f.seek(-2, os.SEEK_CUR)
bytes_written = self.f.write(struct.pack(self.shortFmt, value))
self._verify_bytes_written(bytes_written, 2)
return self._rewriteLast(value, 2)
def rewriteLastLong(self, value: int) -> None:
self.f.seek(-4, os.SEEK_CUR)
bytes_written = self.f.write(struct.pack(self.longFmt, value))
self._verify_bytes_written(bytes_written, 4)
return self._rewriteLast(value, 4)
def writeShort(self, value: int) -> None:
bytes_written = self.f.write(struct.pack(self.shortFmt, value))
@ -2180,32 +2194,22 @@ class AppendingTiffWriter(io.BytesIO):
cur_pos = self.f.tell()
if is_local:
self.fixOffsets(
count, isShort=(field_size == 2), isLong=(field_size == 4)
)
self._fixOffsets(count, field_size)
self.f.seek(cur_pos + 4)
else:
self.f.seek(offset)
self.fixOffsets(
count, isShort=(field_size == 2), isLong=(field_size == 4)
)
self._fixOffsets(count, field_size)
self.f.seek(cur_pos)
elif is_local:
# skip the locally stored value that is not an offset
self.f.seek(4, os.SEEK_CUR)
def fixOffsets(
self, count: int, isShort: bool = False, isLong: bool = False
) -> None:
if not isShort and not isLong:
msg = "offset is neither short nor long"
raise RuntimeError(msg)
def _fixOffsets(self, count: int, field_size: int) -> None:
for i in range(count):
offset = self.readShort() if isShort else self.readLong()
offset = self._read(field_size)
offset += self.offsetOfNewPage
if isShort and offset >= 65536:
if field_size == 2 and offset >= 65536:
# offset is now too large - we must convert shorts to longs
if count != 1:
msg = "not implemented"
@ -2217,10 +2221,19 @@ class AppendingTiffWriter(io.BytesIO):
self.f.seek(-10, os.SEEK_CUR)
self.writeShort(TiffTags.LONG) # rewrite the type to LONG
self.f.seek(8, os.SEEK_CUR)
elif isShort:
self.rewriteLastShort(offset)
else:
self.rewriteLastLong(offset)
self._rewriteLast(offset, field_size)
def fixOffsets(
self, count: int, isShort: bool = False, isLong: bool = False
) -> None:
if isShort:
field_size = 2
elif isLong:
field_size = 4
else:
field_size = 0
return self._fixOffsets(count, field_size)
def _save_all(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None: