implement week-based-year year numbers in strftime

in the process, I refactored the week-number code so it can be used by
the week-based-year formats to determine year adjustments at the
boundary values. this also improves indention/code readability.

diff --git a/src/time/strftime.c b/src/time/strftime.c
index b60197df28a19c2dee757dfdaa01f1119d9f5223..576870589c1a71edeb0fc612e15b22cd35366a8c 100644 (file)
--- a/src/time/strftime.c
+++ b/src/time/strftime.c
@@ -17,6 +17,32 @@ static int is_leap(int y)
        return !(y%4) && ((y%100) || !(y%400));
 }
 
+static int week_num(const struct tm *tm)
+{
+       int val = (tm->tm_yday + 7 - (tm->tm_wday+6)%7) / 7;
+       /* If 1 Jan is just 1-3 days past Monday,
+        * the previous week is also in this year. */
+       if ((tm->tm_wday - tm->tm_yday - 2 + 371) % 7 <= 2)
+               val++;
+       if (!val) {
+               val = 52;
+               /* If 31 December of prev year a Thursday,
+                * or Friday of a leap year, then the
+                * prev year has 53 weeks. */
+               int dec31 = (tm->tm_wday - tm->tm_yday - 1 + 7) % 7;
+               if (dec31 == 4 || (dec31 == 5 && is_leap(tm->tm_year%400-1)))
+                       val++;
+       } else if (val == 53) {
+               /* If 1 January is not a Thursday, and not
+                * a Wednesday of a leap year, then this
+                * year has only 52 weeks. */
+               int jan1 = (tm->tm_wday - tm->tm_yday + 371) % 7;
+               if (jan1 != 4 && (jan1 != 3 || !is_leap(tm->tm_year)))
+                       val = 1;
+       }
+       return val;
+}
+
 size_t strftime(char *restrict s, size_t n, const char *restrict f, const struct tm *restrict tm)
 {
        nl_item item;
@@ -67,14 +93,15 @@ do_fmt:
                        fmt = "%Y-%m-%d";
                        goto recu_strftime;
                case 'g':
-                       // FIXME
-                       val = 0; //week_based_year(tm)%100;
-                       fmt = "%02d";
-                       goto number;
                case 'G':
-                       // FIXME
-                       val = 0; //week_based_year(tm);
                        fmt = "%04d";
+                       val = tm->tm_year + 1900;
+                       if (tm->tm_yday < 3 && week_num(tm) != 1) val--;
+                       else if (tm->tm_yday > 360 && week_num(tm) == 1) val++;
+                       if (*f=='g') {
+                               fmt = "%02d";
+                               val %= 100;
+                       }
                        goto number;
                case 'H':
                        val = tm->tm_hour;
@@ -133,27 +160,7 @@ do_fmt:
                        fmt = "%02d";
                        goto number;
                case 'V':
-                       val = (tm->tm_yday + 7 - (tm->tm_wday+6)%7) / 7;
-                       /* If 1 Jan is just 1-3 days past Monday,
-                        * the previous week is also in this year. */
-                       if ((tm->tm_wday - tm->tm_yday - 2 + 371) % 7 <= 2)
-                               val++;
-                       if (!val) {
-                               val = 52;
-                               /* If 31 December of prev year a Thursday,
-                                * or Friday of a leap year, then the
-                                * prev year has 53 weeks. */
-                               int dec31 = (tm->tm_wday - tm->tm_yday - 1 + 7) % 7;
-                               if (dec31 == 4 || (dec31 == 5 && is_leap(tm->tm_year%400-1)))
-                                       val++;
-                       } else if (val == 53) {
-                               /* If 1 January is not a Thursday, and not
-                                * a Wednesday of a leap year, then this
-                                * year has only 52 weeks. */
-                               int jan1 = (tm->tm_wday - tm->tm_yday + 371) % 7;
-                               if (jan1 != 4 && (jan1 != 3 || !is_leap(tm->tm_year)))
-                                       val = 1;
-                       }
+                       val = week_num(tm);
                        fmt = "%02d";
                        goto number;
                case 'w':