60 lines
1.2 KiB
C
60 lines
1.2 KiB
C
// functions that can move the file position conveniently
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// remember that the last line of a file is usually empty and goes from '\n' to EOF
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#include "move_lines.h"
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#include <unistd.h>
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// function to move back/up
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void go_back_x_lines(int fd, int lines) {
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for (int i = 0; i < lines; i++) {
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seek_previous_line(fd);
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}
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}
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void seek_previous_line(int fd) {
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seek_line_start(fd);
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lseek(fd, -1, SEEK_CUR);
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seek_line_start(fd);
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}
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// set file position to the beginning of the line
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void seek_line_start(int fd) {
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char cur_char = '\0';
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while (cur_char != '\n') {
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int ret_lseek = lseek(fd, -1, SEEK_CUR);
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if (ret_lseek == -1)
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break;
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read(fd, &cur_char, 1);
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if (cur_char != '\n')
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lseek(fd, -1, SEEK_CUR);
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}
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}
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// function to move forward/down
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void go_forward_x_lines(int fd, int lines) {
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for (int i = 0; i < lines; i++) {
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seek_next_line(fd);
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}
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}
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void seek_next_line(int fd) {
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seek_line_end(fd);
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lseek(fd, 1, SEEK_CUR);
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}
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// set file position to the end of the line
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void seek_line_end(int fd) {
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char cur_char = '\0';
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while (cur_char != '\n') {
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// return code 0 of read indicates EOF
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if (read(fd, &cur_char, 1) == 0)
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break;
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}
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lseek(fd, -1, SEEK_CUR);
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}
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