54 lines
1.2 KiB
C
54 lines
1.2 KiB
C
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#include <errno.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/types.h>
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#include <unistd.h>
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typedef struct {
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char elem[2];
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double x, y, z;
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int charge;
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double mass;
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} atom_t;
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void write_atoms(char *fname, atom_t *atoms, int len) {
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int fd = open(fname, O_CREAT | O_WRONLY);
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for (int i = 0; i < len; ++i) {
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write(fd, &atoms[i], sizeof(atom_t));
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}
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close(fd);
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}
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double *read_masses(char *fname, int *setlen) {
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int fd = open(fname, O_RDONLY);
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int size = lseek(fd, 0, SEEK_END);
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double *result = (double *)malloc(size);
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lseek(fd, 0, SEEK_SET);
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int count = 0;
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atom_t atom;
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while (1) {
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int bytes = read(fd, &atom, sizeof(atom_t));
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if (!bytes) break;
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result[count++] = atom.mass;
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}
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close(fd);
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*setlen = count;
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return result;
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}
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int main() {
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atom_t atoms[5] = {{"C", 0.0, 1.0, 2.5, 0, 12.011},
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{"O", 1.0, 3.5, 6.0, 0, 15.999}};
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write_atoms("atoms.dat", atoms, 5);
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int len = -1;
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double *masses = read_masses("atoms.dat", &len);
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printf("read %d masses:\n", len);
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for (int i = 0; i < len; ++i) {
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printf("mass[%d] = %lf\n", i, masses[i]);
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}
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free(masses);
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return 0;
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}
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