kdeng00
41 lines
1010 B
C
41 lines
1010 B
C
/*
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* Simple implementation of getbits() function.
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*
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*/
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#include <stdio.h>
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// Gets n bits from position p
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unsigned getbits(unsigned int x, int p, int n);
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int main()
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{
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// 11111110111 = 1015
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unsigned int x = 1015;
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int p = 4;
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int n = 3;
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// Result is 111 = 7
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unsigned int some_bits = getbits(x, p, n);
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return 0;
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}
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unsigned getbits(unsigned int x, int p, int n)
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{
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printf("(%d >> (%d + 1 - %d)) & ~(~0 << %d)\n", x, p, n, n);
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printf("(%d >> (%d + 1 - %d)) & ~(%d << %d)\n", x, p, n, ~0, n);
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printf("(%d >> (%d + 1 - %d)) & ~(%d)\n", x, p, n, ((~0) << n));
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printf("(%d >> (%d + 1 - %d)) & %d\n", x, p, n, ~((~0) << n));
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printf("(%d >> %d) & %d\n", x, (p + 1 - n), ~((~0) << n));
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printf("%d & %d\n", (x >> (p + 1 - n)), ~((~0) << n));
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printf("%d\n", ((x >> (p + 1 - n)) & ~((~0) << n)));
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// At position 4 and 3 bits from that position of value 1023 is
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// 11111110111 = 1015
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// 110 = 6
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return (x >> (p + 1 - n)) & ~(~0 << n);
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} |