I am trying to understand the documentation re: ctypes and interfacing
with existing libraries.
I am reading the documentation, and also other sites that have largely
just copied the documentation - as well as the "free chapter" at
O'Reilly (Python Cookbook).
I am missing anything on CFields.
My test (template) is:
"""Internal ctypes definitions for AIX libperfstat"""
from sys import maxsize
from ctypes import Structure, Union
from ctypes import c_bool, c_char, c_wchar, c_byte, c_ubyte, c_short,
c_ushort
from ctypes import c_int, c_uint, c_long, c_ulong, c_longlong, c_ulonglong
from ctypes import c_float, c_double, c_longdouble
from ctypes import c_char_p, c_wchar_p, c_void_p
from ctypes import sizeof
IDENTIFIER_LENGTH = 64
class time_t(Structure):
"""
#ifndef _TIME_T
#define _TIME_T
#ifdef _LINUX_SOURCE_COMPAT
typedef long int time_t;
#else /* !_LINUX_SOURCE_COMPAT */
#ifdef __64BIT__
typedef long time_t;
#else
typedef int time_t;
#endif
#endif /* !_LINUX_SOURCE_COMPAT */
#endif
"""
if (maxsize > 2**32):
_fields_ = [("v", c_long)]
else:
_fields_ = [("v", c_int)]
class perfstat_cpu_total_t(Structure):
"""
typedef struct { /* global cpu information */
int ncpus; /* number of active logical processors */
int ncpus_cfg; /* number of configured processors */
char description[IDENTIFIER_LENGTH]; /* processor description
(type/official name) */
u_longlong_t buffer1[15]; /* several variables being skipped
for now */
time_t lbolt; /* number of ticks since last reboot */
u_longlong_t loadavg[3]; /* (1<<SBITS) times the average
number of runnables processes during the last
1, 5 and 15 minutes. */
u_longlong_t buffer2[29]; /* several variables being skipped
for now */
int ncpus_high; /* index of highest processor online */
u_longlong_t puser; /* raw number of physical processor
tics in user mode */
u_longlong_t psys; /* raw number of physical processor
tics in system mode */
u_longlong_t pidle; /* raw number of physical processor
tics idle */
u_longlong_t pwait; /* raw number of physical processor
tics waiting for I/O */
u_longlong_t buffer2[29]; /* several variables being skipped
for now */
} perfstat_cpu_total_t;
"""
_fields_ = [
("ncpus", c_int),
("ncpus_cfg", c_int),
("description", c_char * IDENTIFIER_LENGTH),
("buffer1", c_ulonglong * 15),
("lbolt", time_t),
("loadavg", c_ulonglong * 3),
("buffer2", c_ulonglong * 29),
("ncpus_high", c_int),
("puser", c_ulonglong),
("psys", c_ulonglong),
("pidle", c_ulonglong),
("pwait", c_ulonglong),
("buffer3", c_ulonglong * 12)
]
xxx = time_t
print xxx
print xxx.v
print sizeof(xxx)
# print sizeof(xxx.v)
xxx = perfstat_cpu_total_t
print xxx
print xxx.lbolt
print sizeof(xxx)
# print sizeof(xxx.lbolt)
xxx = xxx.lbolt
print xxx
print xxx.value
result:
michael@x071:[/data/prj/python/cloud-init/aix-cloud-init-0.7.8.1/new]python
test*
<class '__main__.time_t'>
<Field type=c_long, ofs=0, size=8>
8
<class '__main__.perfstat_cpu_total_t'>
<Field type=time_t, ofs=192, size=8>
592
<Field type=time_t, ofs=192, size=8>
Traceback (most recent call last):
File "test_1.py", line 79, in <module>
print xxx.value
AttributeError: '_ctypes.CField' object has no attribute 'value'
Question:
a) where is documentation on "CField"'s? I have not been successful with
google - :(
b) what I am not understanding - as the basic documentation shows
FOO.value as the way to set/get the value of a _field_
+++
I assume I am not understanding something from the base documentation at
https://docs.python.org/2/library/ctypes.html#Structured-data-types
Hints, improved links, etc are appreciated!
--
https://mail.python.org/mailman/listinfo/python-list
