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Created on 2013年06月15日 16:42 by Tomer.Levi, last changed 2022年04月11日 14:57 by admin. This issue is now closed.
| Messages (3) | |||
|---|---|---|---|
| msg191213 - (view) | Author: Tomer Levi (Tomer.Levi) | Date: 2013年06月15日 16:42 | |
Whenever you create a ctypes.Structure with mixed ctypes, the size of all components is calculated by the size of largest one. This is especially irritating when trying to use Structure on bytearray.
The problem repeated for me in Python2.6 and 2.7 (both 32bit and 64bit versions) [My computer is 64bit]
Example:
#Creating a Structure that should take up 5 bytes
class Test(ctypes.Structure):
_fields_ = [("test", ctypes.c_byte),
("test2", ctypes.c_uint32),]
#Initiating the Structure
Test.from_buffer(bytearray(5))
--- OUTPUT ----
Traceback (most recent call last):
File "<ipython-input-45-cd4b7501baee>", line 1, in <module>
Test.from_buffer(bytearray(5))
ValueError: Buffer size too small (5 instead of at least 8 bytes)
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| msg191214 - (view) | Author: Alex Gaynor (alex) * (Python committer) | Date: 2013年06月15日 16:45 | |
This is how padding works in the C ABI, not a bug. |
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| msg191340 - (view) | Author: Amaury Forgeot d'Arc (amaury.forgeotdarc) * (Python committer) | Date: 2013年06月17日 14:30 | |
You can also use "_pack_ = 1" to override the default alignment rules: http://docs.python.org/3/library/ctypes.html#ctypes.Structure._pack_ |
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| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2022年04月11日 14:57:46 | admin | set | github: 62425 |
| 2013年06月17日 14:30:39 | amaury.forgeotdarc | set | nosy:
+ amaury.forgeotdarc messages: + msg191340 |
| 2013年06月15日 16:45:39 | alex | set | status: open -> closed nosy: + alex messages: + msg191214 resolution: not a bug |
| 2013年06月15日 16:42:24 | Tomer.Levi | create | |