59 lines
1.2 KiB
C
59 lines
1.2 KiB
C
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#include <sys/stat.h>
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#include <sys/fcntl.h>
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#include <sys/mman.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <stdio.h>
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#include <string.h>
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#include <assert.h>
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int main(int argc, char *argv[])
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{
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int fin;
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struct stat st;
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if (argc != 2)
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{
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fprintf(stderr, "Usage: %s <file>\n", argv[0]);
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return 1;
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}
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fin = open(argv[1], O_RDWR);
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assert(fin >= 0);
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fstat(fin, &st);
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if (st.st_nlink > 1)
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{
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unlink(argv[1]);
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close(fin);
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return 0;
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}
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char *src = mmap(NULL, st.st_size, PROT_WRITE, MAP_SHARED, fin, 0);
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assert(src != MAP_FAILED);
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memset(src, 0xff, st.st_size);
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munmap(src, st.st_size);
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src = mmap(NULL, st.st_size, PROT_WRITE, MAP_SHARED, fin, 0);
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assert(src != MAP_FAILED);
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int urandom = open("/dev/urandom", O_RDONLY);
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assert(urandom >= 0);
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ssize_t r = read(urandom, src, st.st_size);
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assert(r == st.st_size);
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munmap(src, st.st_size);
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char new_name[64];
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r = read(urandom, new_name, sizeof(new_name));
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assert(r == sizeof(new_name));
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close(urandom);
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close(fin);
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rename(argv[1], new_name);
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remove(new_name);
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}
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