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annotate python/pydc/examples/callback.py @ 54:918dab7a6606

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- added callback support (comes with some bigger refactoring) - allow CPython's Py{CObject,Capsule} to be used as 'p'ointers
author Tassilo Philipp
date Tue, 02 Feb 2021 20:42:02 +0100
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children 16151547265e
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54
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1 # callback of python function to qsort(3) some numbers - this is just a example
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2 # using an existing libc function that uses a callback; it's not practical for
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3 # real world use as it comes with a huge overhead:
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4 # - sorting requires many calls of the comparison function
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5 # - each such callback back into python comes with a lot of overhead
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6 # - on top of that, for this example, 2 memcpy(3)s are needed to access the
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7 # data to compare, further adding to the overhead
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9 from pydc import *
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10 import sys
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11 import platform
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12 import struct
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14 if sys.platform == "win32":
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15 libc = load("msvcrt")
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16 elif sys.platform == "darwin":
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17 libc = load("/usr/lib/libc.dylib")
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18 elif "bsd" in sys.platform:
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19 #libc = load("/usr/lib/libc.so")
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20 libc = load("/lib/libc.so.7")
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21 elif platform.architecture()[0] == "64bit":
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22 libc = load("/lib64/libc.so.6")
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23 else:
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24 libc = load("/lib/libc.so.6")
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28 fp_qsort = find(libc,"qsort") # void qsort(void *base, size_t nmemb, size_t size, int (*compar)(const void *, const void *));
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29 fp_memcpy = find(libc,"memcpy") # void * memcpy(void *dst, const void *src, size_t len);
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33 nums = bytearray(struct.pack("i"*8, 12, 3, 5, 99, 3, -9, -9, 0))
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34 es = int(len(nums)/8) # element size
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37 def compar(a, b):
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38 ba = bytearray(es)
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39 call(fp_memcpy,"ppi)p", ba, a, es)
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40 a = struct.unpack("i", ba)[0]
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41 call(fp_memcpy,"ppi)p", ba, b, es)
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42 b = struct.unpack("i", ba)[0]
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43 return a - b
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44
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45 cb = new_callback("pp)i", compar)
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46
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47 # --------
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48
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49 print(*struct.unpack("i"*8, nums))
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51 print('... qsort ...')
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52 call(fp_qsort,"piip)v", nums, 8, es, cb)
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54 print(*struct.unpack("i"*8, nums))
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57 free_callback(cb)
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