31 lines
860 B
C
31 lines
860 B
C
#include <stdbool.h>
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#include <stddef.h>
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#include <stdio.h>
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bool damm(unsigned char *input, size_t length) {
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static const unsigned char table[10][10] = {
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{0, 3, 1, 7, 5, 9, 8, 6, 4, 2},
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{7, 0, 9, 2, 1, 5, 4, 8, 6, 3},
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{4, 2, 0, 6, 8, 7, 1, 3, 5, 9},
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{1, 7, 5, 0, 9, 8, 3, 4, 2, 6},
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{6, 1, 2, 3, 0, 4, 5, 9, 7, 8},
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{3, 6, 7, 4, 2, 0, 9, 5, 8, 1},
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{5, 8, 6, 9, 7, 2, 0, 1, 3, 4},
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{8, 9, 4, 5, 3, 6, 2, 0, 1, 7},
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{9, 4, 3, 8, 6, 1, 7, 2, 0, 5},
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{2, 5, 8, 1, 4, 3, 6, 7, 9, 0},
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};
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unsigned char interim = 0;
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for (size_t i = 0; i < length; i++) {
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interim = table[interim][input[i]];
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}
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return interim == 0;
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}
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int main() {
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unsigned char input[4] = {5, 7, 2, 4};
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puts(damm(input, 4) ? "Checksum correct" : "Checksum incorrect");
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return 0;
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}
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