95 lines
2.9 KiB
C
95 lines
2.9 KiB
C
#include <time.h>
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#include <stdio.h>
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static const char *day_names[7] = {
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"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday",
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"Saturday",
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};
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static const char *month_names[12] = {
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"January", "February", "March", "April", "May", "June", "July",
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"August", "September", "October", "November", "December",
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};
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/* Perform a call to snprintf() to print a value */
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#define do_snprintf(...) { \
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size_t _written = snprintf(s+len, n-len, __VA_ARGS__); \
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len += _written; \
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if(len >= n) goto full; \
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}; break
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/* Perform a sub-call to strftime to expand a complex format */
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#define do_strftime(fmt) { \
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size_t _written = strftime(s+len, n-len, fmt, time); \
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if(_written == 0) goto full; \
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len += _written; \
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}; break
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size_t strftime(char * restrict s, size_t n, const char * restrict format,
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const struct tm * restrict time)
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{
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size_t len = 0;
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while(*format) {
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if(*format != '%') {
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s[len++] = *format++;
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if(len >= n) goto full;
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continue;
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}
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format++;
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int c = *format++;
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/* In the "C" locale, ignore modifiers E and O */
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if(c == 'E') c = *format++;
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else if(c == 'O') c = *format++;
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switch(c) {
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case 'a': do_snprintf("%.3s", day_names[time->tm_wday]);
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case 'A': do_snprintf("%s", day_names[time->tm_wday]);
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case 'b': do_snprintf("%.3s", month_names[time->tm_mon]);
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case 'B': do_snprintf("%s", month_names[time->tm_mon]);
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case 'c': do_strftime("%a %b %e %T %Y");
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case 'C': do_snprintf("%02d", (time->tm_year + 1900) / 100);
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case 'd': do_snprintf("%02d", time->tm_mday);
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case 'D': do_strftime("%m/%d/%y");
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case 'e': do_snprintf("%2d", time->tm_mday);
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case 'F': do_strftime("%Y-%m-%d");
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/* TODO: strftime: Support week-based year */
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case 'g': do_snprintf("??");
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case 'G': do_snprintf("????");
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case 'h': do_strftime("%b");
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case 'H': do_snprintf("%02d", time->tm_hour);
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case 'I': do_snprintf("%02d", (time->tm_hour+11)%12 + 1);
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case 'j': do_snprintf("%03d", time->tm_yday + 1);
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case 'm': do_snprintf("%02d", time->tm_mon + 1);
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case 'M': do_snprintf("%02d", time->tm_min);
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case 'n': do_snprintf("\n");
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case 'p': do_snprintf(time->tm_hour < 12 ? "AM" : "PM");
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case 'r': do_strftime("%I:%M:%S %p");
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case 'R': do_strftime("%H:%M");
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case 'S': do_snprintf("%02d", time->tm_sec);
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case 't': do_snprintf("\t");
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case 'T': do_strftime("%H:%M:%S");
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case 'u': do_snprintf("%d", (time->tm_wday+6) % 7 + 1);
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/* TODO: strftime: Support week number */
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case 'U': do_snprintf("??");
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case 'V': do_snprintf("??");
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case 'w': do_snprintf("%d", time->tm_wday);
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case 'W': do_snprintf("??");
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case 'x': do_strftime("%m/%d/%y");
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case 'X': do_strftime("%T");
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case 'y': do_snprintf("%02d", time->tm_year % 100);
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case 'Y': do_snprintf("%d", time->tm_year + 1900);
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/* TODO: strftime: Support timezones */
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case 'z': break;
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case 'Z': break;
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case '%': do_snprintf("%%");
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}
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}
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s[len] = 0;
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return len;
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full:
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s[n-1] = 0;
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return 0;
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}
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