Macintosh-Tools/python-rsrcfork
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Remove custom stream types and read all resource data upfront again

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The custom stream types were almost always slower than just reading the
entire data into memory, and there's no reason not to do that -
resources are small enough that memory usage and disk IO speed aren't a
concern (at least not for any machine that's modern enough to run
Python 3...).

Perhaps the only performance advantage was when reading a small amount
of data from the start of a compressed resource. In that case the
custom stream could incrementally decompress only the part of the data
that's actually needed, which was a bit faster than decompressing the
entire resource and then throwing away most of the data. But this
situation is rare enough that it's not worth handling in the rsrcfork
library. If this is a real performance issue for someone, they can
manually call the incremental decompression functions from
rsrcfork.compress where needed.
This commit is contained in:
dgelessus
2020-11-01 19:28:25 +01:00
parent d74dbc41ba
commit 5c3bc5d7e5
3 changed files with 7 additions and 170 deletions
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rsrcfork/api.py
+7 -11
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@@ -179,8 +179,8 @@ class Resource(object):
try:
return self._data_raw
except AttributeError:
with self.open_raw() as f:
self._data_raw = f.read()
self._resfile._stream.seek(self._resfile.data_offset + self.data_raw_offset + STRUCT_RESOURCE_DATA_HEADER.size)
self._data_raw = _io_utils.read_exact(self._resfile._stream, self.length_raw)
return self._data_raw
def open_raw(self) -> typing.BinaryIO:
@@ -196,7 +196,7 @@ class Resource(object):
because the stream API does not require the entire resource data to be read in advance.
"""
return _io_utils.make_substream(self._resfile._stream, self._resfile.data_offset + self.data_raw_offset + STRUCT_RESOURCE_DATA_HEADER.size, self.length_raw)
return io.BytesIO(self.data_raw)
@property
def compressed_info(self) -> typing.Optional[compress.common.CompressedHeaderInfo]:
@@ -252,8 +252,9 @@ class Resource(object):
try:
return self._data_decompressed
except AttributeError:
with self.open() as f:
self._data_decompressed = f.read()
with self.open_raw() as compressed_f:
compressed_f.seek(self.compressed_info.header_length)
self._data_decompressed = b"".join(compress.decompress_stream_parsed(self.compressed_info, compressed_f))
return self._data_decompressed
else:
return self.data_raw
@@ -271,12 +272,7 @@ class Resource(object):
because the stream API does not require the entire resource data to be read (and possibly decompressed) in advance.
"""
if self.compressed_info is None:
return self.open_raw()
else:
f = self.open_raw()
f.seek(self.compressed_info.header_length)
return compress.DecompressingStream(f, self.compressed_info, close_stream=True)
return io.BytesIO(self.data)
class _LazyResourceMap(typing.Mapping[int, Resource]):