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Bug 1641073: improve BaseFile.copy() performance r=rstewart

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Arrays are mutable, so appending each substring at a time and joining at the endis much faster than re-allocating
a new string on each loop.

Differential Revision: https://phabricator.services.mozilla.com/D76945
This commit is contained in:
Mitchell Hentges 2020-05-27 16:52:51 +00:00
parent 812a214eeb
commit 0482fe58ed
1 changed files with 3 additions and 3 deletions
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6
python/mozbuild/mozpack/files.py
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@ -228,18 +228,18 @@ class BaseFile(object):
return True
src = self.open()
copy_content = b''
accumulated_src_content = []
while True:
dest_content = dest.read(32768)
src_content = src.read(32768)
copy_content += src_content
accumulated_src_content.append(src_content)
if len(dest_content) == len(src_content) == 0:
break
# If the read content differs between origin and destination,
# write what was read up to now, and copy the remainder.
if (six.ensure_binary(dest_content) !=
six.ensure_binary(src_content)):
dest.write(copy_content)
dest.write(b''.join(accumulated_src_content))
shutil.copyfileobj(src, dest)
break
if hasattr(self, 'path') and hasattr(dest, 'path'):