155 lines
3.6 KiB
C
155 lines
3.6 KiB
C
#include <stdio.h> /* printf, scanf */
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#include <stdbool.h> /* bool */
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#include <string.h> /* strerror */
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#include <time.h> /* time_t, time, localtime */
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#include <ctype.h> /* toupper */
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#include <errno.h> /* errno */
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#include <stdlib.h> /* atoi */
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#include "time.h"
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#define TIME_ERR_RESULT ((time_t) -1)
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#define LOCALTIME_ERR_RESULT NULL
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#define ERR_MSG_SIZE 128
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static const char *AM="AM";
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static const char *PM="PM";
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static char *to_upper_case(char *s);
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static void set_err_msg(char *prefix, int errno);
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static void copy_struct_tm(struct tm *dest, struct tm *src);
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static const char *convert_24_hour_to_meridiem(uint8_t hours);
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static uint8_t convert_12_hour_to_24_hour(uint8_t twelve_hour, char *meridiem);
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static void convert_24_hour_to_12_hour(uint8_t twenty_four_hour, uint8_t *twelve_hour, char const **meridiem);
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static char G_err_msg[ERR_MSG_SIZE];
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void copy_struct_tm(struct tm *dest, struct tm *src)
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{
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dest->tm_sec = src->tm_sec;
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dest->tm_min = src->tm_sec;
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dest->tm_hour = src->tm_hour;
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dest->tm_mday = src->tm_mday;
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dest->tm_mon = src->tm_mon;
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dest->tm_year = src->tm_year;
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dest->tm_wday = src->tm_wday;
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dest->tm_yday = src->tm_wday;
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dest->tm_isdst = src->tm_isdst;
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}
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static const char *convert_24_hour_to_meridiem(uint8_t hours)
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{
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if (hours < 12) {
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return AM;
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}
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else {
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return PM;
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}
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}
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static uint8_t convert_12_hour_to_24_hour(uint8_t twelve_hour, char *meridiem)
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{
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uint8_t twenty_four_hour;
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/* Default */
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twenty_four_hour = twelve_hour;
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/* Special cases */
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if (strcmp(meridiem, AM) == 0) {
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if (twelve_hour == 12) {
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twenty_four_hour = 0;
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}
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}
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else if (twelve_hour < 12) {
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twenty_four_hour = twelve_hour + 12;
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}
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return twenty_four_hour;
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}
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void convert_24_hour_to_12_hour(uint8_t twenty_four_hour, uint8_t *twelve_hour, char const **meridiem)
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{
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if (twenty_four_hour == 0) {
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*twelve_hour = 12;
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}
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else if (twenty_four_hour < 12) {
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*meridiem = AM;
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}
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else if (twenty_four_hour == 12) {
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*meridiem = PM;
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}
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else {
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*twelve_hour = twenty_four_hour - 12;
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*meridiem = PM;
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}
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}
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void set_err_msg(char *what_failed, int err_code)
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{
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snprintf(G_err_msg, ERR_MSG_SIZE, "%s: %s", what_failed, strerror(err_code));
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}
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bool load_system_time(struct tm *t)
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{
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time_t now;
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struct tm *now_breakdown;
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bool success = false;
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if (time(&now) != TIME_ERR_RESULT) {
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if ((now_breakdown = localtime(&now)) != LOCALTIME_ERR_RESULT) {
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copy_struct_tm(t, now_breakdown);
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success = true;
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}
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else {
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perror("Localtime failed");
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}
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}
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else {
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perror("Time function failed");
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}
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return success;
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}
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char *to_upper_case(char *s)
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{
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size_t i;
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for (i = 0; s[i] != '\0'; ++i) {
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s[i] = toupper(s[i]);
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}
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return s;
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}
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void read_time_interactively(struct tm *t)
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{
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char line[4];
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int8_t hour;
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int8_t min;
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printf("Hour:");
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hour = atoi(fgets(line, sizeof(line), stdin));
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printf("Minute:");
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min = atoi(fgets(line, sizeof(line), stdin));
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printf("AM or PM:");
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fgets(line, sizeof(line), stdin);
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t->tm_hour = convert_12_hour_to_24_hour(hour, line);
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t->tm_min = min;
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t->tm_sec = 0;
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}
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void print_12_hour_time(struct tm *t)
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{
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uint8_t hour;
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const char *meridiem;
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convert_24_hour_to_12_hour(t->tm_hour, &hour, &meridiem);
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printf("%2hu:%02d:%02d %2s", hour, t->tm_min, t->tm_sec, meridiem);
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}
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void reprint_12_hour_time(struct tm *t)
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{
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printf("\b\b\b\b\b\b\b\b\b\b\b");
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print_12_hour_time(t);
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}
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