ref: 297c3c7dfa958231abe140ee00d38b0e684ad48c
dir: /src/libc/time/strftime.c/
#include <string.h> #include <time.h> #include "../libc.h" #undef strftime static char *days[] = { "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", }; static char *months[] = { "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" }; static char *am_pm[] = {"AM", "PM"}; static int first(int day, int year) { int ny; ny = _newyear(year); if (ny == day) return 0; if (day - ny < 0) return 7 - (ny - day); return day - ny; } static int weeknum(struct tm *tm, int day) { int fday, val; fday = first(day, tm->tm_year); if (tm->tm_yday < fday) { val = 0; } else { val = tm->tm_yday - fday; val /= 7; val++; } return val; } static int isoyear(struct tm *tm) { int monday; if (tm->tm_yday < 7) { monday = first(THU, tm->tm_year) - 3; if (tm->tm_yday < monday) return tm->tm_year - 1; } else if (tm->tm_yday > 357) { monday = first(THU, tm->tm_year + 1) - 3; if (tm->tm_mday >= (31 + monday)) return tm->tm_year + 1; } return tm->tm_year; } static int isoweek(struct tm *tm) { int year, monday, yday, val; year = isoyear(tm); monday = first(THU, year) - 3; yday = tm->tm_yday; if (year > tm->tm_year) yday = tm->tm_mday - 31 + monday; else if (year < tm->tm_year) yday = _daysyear(year) + yday; val = yday - monday; val /= 7; val++; return val; } static int isoday(struct tm *tm) { if (tm->tm_wday == 0) return 7; return tm->tm_wday; } static size_t sval(char *s, size_t siz, char **strs, int abrev, int idx, int max) { char *str; size_t len; if (idx < 0 && idx >= max) goto wrong; str = strs[idx]; len = (!abrev) ? strlen(str) : 3; if (len > siz) goto wrong; memcpy(s, str, len); return len; wrong: *s = '?'; return 1; } static size_t dval(char *s, size_t siz, int prec, int fill, int val) { char *t; int n; static char digits[] = "0123456789"; if (prec > siz || val < 0) { *s = '?'; return 1; } n = prec; do { s[--n] = digits[val % 10]; val /= 10; } while (n > 0 && val > 0); while (n > 0) s[--n] = fill; return prec; } static size_t timezone(char *s, size_t prec, const struct tm * restrict tm) { long off = tm->tm_gmtoff; if (prec < 5) { *s = '?'; return 1; } if (off >= 0) { *s++ = '+'; } else { *s++ = '-'; off = -off; } dval(s, 2, 2, '0', off / 3600); dval(s, 2, 2, '0', (off % 3600) / 60); return 5; } size_t strftime(char *restrict s, size_t maxsize, const char *restrict format, const struct tm *restrict timeptr) { int ch, abrev, val, fill, width; size_t n, inc; char *tfmt; for (n = --maxsize; (ch = *format++) && n > 0; s += inc, n -= inc) { if (ch != '%') { *s = ch; inc = 1; continue; } abrev = 0; fill = '0'; width = 2; if (*format == 'E' || *format == 'O') format++; switch (*format++) { case 'a': abrev = 1; case 'A': inc = sval(s, n, days, abrev, timeptr->tm_wday, 7); break; case 'h': case 'b': abrev = 1; case 'B': inc = sval(s, n, months, abrev, timeptr->tm_mon, 12); break; case 'c': tfmt = "%a %b %e %T %Y"; goto recursive; case 'C': val = (timeptr->tm_year + 1900) / 100; goto number; case 'd': val = timeptr->tm_mday; goto number; case 'D': tfmt = "%m/%d/%y"; goto recursive; case 'e': fill = ' '; val = timeptr->tm_mday; goto number; case 'F': tfmt = "%Y-%m-%d"; goto recursive; case 'g': val = isoyear(timeptr); goto number; case 'G': val = isoyear(timeptr); val += 1900; width = 4; goto number; case 'H': val = timeptr->tm_hour; goto number; case 'I': val = timeptr->tm_hour; if (val == 0) val = 12; if (val > 12) val -= 12; goto number; case 'j': width = 3; val = timeptr->tm_yday+1; goto number; case 'm': val = timeptr->tm_mon+1; goto number; case 'M': val = timeptr->tm_min; goto number; case 'n': val = '\n'; goto character; case 'p': inc = sval(s, n, am_pm, 0, timeptr->tm_hour > 12, 2); break; case 'r': tfmt = "%I:%M:%S %p"; goto recursive; case 'R': tfmt = "%H:%M"; goto recursive; case 'S': val = timeptr->tm_sec; goto number; case 't': val = '\t'; goto character; case 'u': width = 1; val = isoday(timeptr); goto number; case 'U': val = weeknum(timeptr, SUN); goto number; case 'V': val = isoweek(timeptr); goto number; case 'w': width = 1; val = timeptr->tm_wday; goto number; case 'W': val = weeknum(timeptr, MON); goto number; case 'X': case 'T': tfmt = "%H:%M:%S"; goto recursive; case 'x': tfmt = "%m/%d/%y"; goto recursive; case 'y': val = timeptr->tm_year%100; goto number; case 'Y': width = 4; val = 1900 + timeptr->tm_year; goto number; case 'z': inc = timezone(s, n, timeptr); break; case 'Z': memcpy(s, timeptr->tm_zone, 3); inc = 3; break; case '\0': inc = 0; --format; break; case '%': val = '%'; character: *s = val; inc = 1; break; number: inc = dval(s, n, width, fill, val); break; recursive: inc = strftime(s, n+1, tfmt, timeptr); break; } } *s = '\0'; return maxsize - n; }