48 lines
833 B
C
48 lines
833 B
C
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#include <stdio.h>
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#include <assert.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <fcntl.h>
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#define MASK_BIT_7 0x80
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#define MASK_BIT_6 0x40
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#define MASK_BIT_5 0x20
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#define MASK_BIT_4 0x10
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#define MASK_BIT_3 0x08
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#define MASK_BIT_2 0x04
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#define MASK_BIT_1 0x02
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#define MASK_BIT_0 0x01
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unsigned char next(unsigned char lfsr)
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{
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lfsr = (lfsr << 1);
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if(__builtin_parity(lfsr)==0){
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lfsr ^= 1 << 0;
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}
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return lfsr;
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}
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int main(int argc, char *argv[])
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{
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int fd_in,fd_out;
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unsigned char w,buf;;
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assert(argc >= 4);
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fd_in = open(argv[1],O_RDONLY);
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fd_out = open(argv[2],O_WRONLY|O_TRUNC|O_CREAT,0600);
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w = (unsigned char)strtol(argv[3],NULL,0);
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while(1){
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ssize_t nb = read(fd_in,&buf,1);
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if (nb <=0)
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break;
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buf ^= w;
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write(fd_out,&buf,1);
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w=next(w);
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}
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return 0;
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}
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