119 lines
2.6 KiB
C
Executable File
119 lines
2.6 KiB
C
Executable File
#include <stdio.h>
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#include <stdlib.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <sys/file.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <limits.h>
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#include <errno.h>
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enum
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{
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ARGS_NUM = 2,
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};
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int
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safe_read(int fd, void *buf, size_t count)
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{
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errno = 0;
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size_t bytes_read = 0;
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while (bytes_read < count) {
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ssize_t res = read(fd, buf + bytes_read, count - bytes_read);
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if (res < 0) {
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if (errno == EINTR) {
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errno = 0;
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continue;
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}
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fprintf(stderr, "Error reading from file descriptor %d\n", fd);
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close(fd);
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exit(1); // TODO: по-хорошему заменить на внешний обработчик ошибок
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}
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if (res == 0) {
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break;
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}
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bytes_read += res;
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}
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return bytes_read;
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}
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int
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safe_write(int fd, void *buf, size_t count)
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{
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errno = 0;
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size_t bytes_written = 0;
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while (bytes_written < count) {
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ssize_t res = write(fd, buf + bytes_written, count - bytes_written);
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if (res < 0) {
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if (errno == EINTR) {
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errno = 0;
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continue;
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}
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fprintf(stderr, "Error writing to file descriptor %d\n", fd);
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close(fd);
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exit(1); // TODO: по-хорошему заменить на внешний обработчик ошибок
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}
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bytes_written += res;
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}
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return bytes_written;
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}
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int
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main(int argc, char *argv[])
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{
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if (argc != ARGS_NUM) {
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fprintf(stderr, "Wrong number of arguments\n");
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return 1;
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}
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int fd = open(argv[1], O_RDWR);
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if (fd == -1) {
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fprintf(stderr, "Error opening file %s\n", argv[1]);
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return 1;
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}
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long long num, min_num = LLONG_MAX;
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off_t pt_min = -1;
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while (safe_read(fd, &num, sizeof(num)) == sizeof(num)) {
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if (num < min_num || pt_min == -1) {
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min_num = num;
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if ((pt_min = lseek(fd, 0, SEEK_CUR) - sizeof(num)) == -1) {
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fprintf(stderr, "Error in navigate file %s\n", argv[1]);
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return 1;
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}
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}
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}
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if (min_num != LLONG_MIN && pt_min != -1) {
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min_num = -min_num;
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if (lseek(fd, pt_min, SEEK_SET) == -1) {
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fprintf(stderr, "Error in navigate file %s\n", argv[1]);
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return 1;
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}
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if (safe_write(fd, &min_num, sizeof(min_num)) != sizeof(num)) {
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printf("Error while writing");
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return 1;
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}
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}
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close(fd);
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return 0;
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}
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