Speed up EnumKey call

[garth42]

BPO	977553
Nosy	@loewis, @theller, @birkenfeld
Files	_winreg_enumkey_speedup.patch: Patch to spped up _winreg.EnumKey winreg-enumkey.diff: revised patch

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2006-02-18.23:37:35.000>
created_at = <Date 2004-06-22.15:22:11.000>
labels = ['OS-windows']
title = 'Speed up EnumKey call'
updated_at = <Date 2006-02-18.23:37:35.000>
user = 'https://bugs.python.org/garth42'

bugs.python.org fields:

activity = <Date 2006-02-18.23:37:35.000>
actor = 'georg.brandl'
assignee = 'none'
closed = True
closed_date = None
closer = None
components = ['Windows']
creation = <Date 2004-06-22.15:22:11.000>
creator = 'garth42'
dependencies = []
files = ['6045', '6046']
hgrepos = []
issue_num = 977553
keywords = ['patch']
message_count = 9.0
messages = ['46206', '46207', '46208', '46209', '46210', '46211', '46212', '46213', '46214']
nosy_count = 6.0
nosy_names = ['loewis', 'theller', 'georg.brandl', 'garth42', 'alanmcintyre', 'mmangino']
pr_nums = []
priority = 'high'
resolution = 'accepted'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue977553'
versions = ['Python 2.4']

[garth42]

This patch removes the RegQueryInfoKey call and
replaces it with a call to EnumKeyEx. This greatly
speeds up this call.

The script below times

python 2.3 5531 89.7130000591
python 2.4 +patch 5531 0.0469999313354

start = time.time()
i = 0
try:
  while 1:
    _winreg.EnumKey(_winreg.HKEY_CLASSES_ROOT, i)
    i += 1
except WindowsError:
  pass
print i, time.time() - start

[mmangino]

Logged In: YES
user_id=74879

This looks good to me, but I think the buffer size is off by
one. I read the SDK to say tha they key can be 255
characters. That means you need to allocate 256 characters
to allow for the null terminator. Could you create a test
case for a max length registry key?

[theller]

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user_id=11105

I'm curious: Why did you replace RegEnumKey with
RegEnumKeyEx? Are there any advantages of the latter?

[garth42]

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user_id=45280

mmangino:

Yes you're correct it should be 256 in both cases. Doh! I'll
attach a new patch in a while. but It's easy to mmodify the
patch and up the linit to 256

theller:

The advantage of the latter is it returns the Length of the
string returned so we can pass it straight back to the
string creation funtion in python without a strlen.

also the SDK says this....

Note This function is provided only for compatibility with
16-bit versions of Windows. Applications should use the
RegEnumKeyEx function.

[loewis]

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user_id=21627

Also, please follow the Python style guide for C code, PEP-7. In particular:

• use tabs for indentation, with a tab being worth 8 spaces
• omit spaces after opening and before closing parens
• put the opening brace of a code block on the same line as
  the keyword

[alanmcintyre]

Logged In: YES
user_id=1115903

I think it's a good idea to get 16-bit Windows functions out
of Python per Microsoft's recommendation, especially when
doing so can also help performance.

It looks like this patch still needs some cleanup and a test
or two. If nobody else wants to do it I can probably finish
it up.

[loewis]

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user_id=21627

garth42, can you please indicate whether you are willing to
work on the patch, and if so in what time frame?

[birkenfeld]

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user_id=1188172

Attached a revised patch following coding style and adding
additional error handling.

winreg-enumkey.diff

[birkenfeld]

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user_id=1188172

Cleaned up and committed in rev. 42475.