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annotate python/pydc/examples/callback.py @ 60:8e905c0798c7

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- p2Z() helper func - import fix for test code avoiding potential circular import
author Tassilo Philipp
date Wed, 03 Aug 2022 15:38:07 +0200
parents 16151547265e
children
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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 random
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13 import struct
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15 if sys.platform == "win32":
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16 libc = load("msvcrt")
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17 elif sys.platform == "darwin":
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18 libc = load("/usr/lib/libc.dylib")
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19 elif "bsd" in sys.platform:
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20 #libc = load("/usr/lib/libc.so")
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21 libc = load("/lib/libc.so.7")
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22 elif platform.architecture()[0] == "64bit":
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23 libc = load("/lib64/libc.so.6")
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24 else:
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25 libc = load("/lib/libc.so.6")
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29 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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30 fp_memcpy = find(libc,"memcpy") # void * memcpy(void *dst, const void *src, size_t len);
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34 n = 8
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35 nums = bytearray(struct.pack("i"*n, *[random.randrange (-10, 50) for i in range (n)]))
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36 es = int(len(nums)/n) # element size
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39 def compar(a, b):
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40 ba = bytearray(es)
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41 call(fp_memcpy,"ppi)p", ba, a, es)
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42 a = struct.unpack("i", ba)[0]
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43 call(fp_memcpy,"ppi)p", ba, b, es)
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44 b = struct.unpack("i", ba)[0]
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45 return a - b
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47 cb = new_callback("pp)i", compar)
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49 # --------
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51 print('%d '*n % struct.unpack("i"*n, nums))
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53 print('... qsort ...')
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54 call(fp_qsort,"piip)v", nums, n, es, cb)
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56 print('%d '*n % struct.unpack("i"*n, nums))
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59 free_callback(cb)
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