use pregenerated CRC32 lookup tables for retain on Win32 and GNU/Linux

This code could be possible reused on low-end targets with limited RAM.

code to generate lookup table:
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/* CRC lookup table and initial state. */
uint32_t crc32_table[256];

/* Generate CRC32 lookup table. */
void GenerateCRC32Table(void)
{
unsigned int i, j;
/* Use CRC-32-IEEE 802.3 polynomial 0x04C11DB7 (bit reflected). */
uint32_t poly = 0xEDB88320;

for (i = 0; i <= 0xFF; i++)
{
uint32_t c = i;
for (j = 0 ; j < 8 ; j++)
c = (c & 1) ? (c >> 1 ) ^ poly : (c >> 1);
crc32_table[i] = c;
}
}

void main(void)
{
GenerateCRC32Table();
int j=0;
for(int i=0; i<256; i++) {
printf("0x%08X, ", crc32_table[i]);
if (++j >= 8) {
j = 0;
printf("\n");
}
}
}
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#!/usr/bin/env python

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# -*- coding: utf-8 -*-

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#

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# See COPYING.Runtime file for copyrights details.

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#

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from __future__ import absolute_import

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from ctypes import CDLL, RTLD_GLOBAL, pointer, c_int, POINTER, c_char, create_string_buffer

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def TryPreloadXenomai():

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    """

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    Xenomai 3 (at least for version <= 3.0.6) do not handle properly dlclose

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    of shared objects whose dlopen did trigger xenomai_init.

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    As a workaround, this pre-loads xenomai libraries that need to be

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    initialized and call xenomai_init once for all.

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    Xenomai auto init of libs MUST be disabled (see --auto-init-solib in xeno-config)

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    """

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    try:

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        for name in ["cobalt", "modechk", "copperplate", "alchemy"]:

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            globals()[name] = CDLL("lib"+name+".so", mode=RTLD_GLOBAL)

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        cobalt.xenomai_init(pointer(c_int(0)), pointer((POINTER(c_char)*2)(create_string_buffer("prog_name"), None)))

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    except Exception:

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        pass