1 files changed, 143 insertions, 0 deletions
diff --git a/user/lib/timetostr.c b/user/lib/timetostr.c
new file mode 100644
index 0000000..fa77362
--- /dev/null
+++ b/user/lib/timetostr.c
@@ -0,0 +1,143 @@
+#include <lib.h>
+#include <time.h>
+
+static char *ABB_WEEKDAY[7] = {
+	"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
+};
+
+static char *FULL_WEEKDAY[7] = { "Sunday",	 "Monday", "Tuesday", "Wednesday",
+								 "Thursday", "Friday", "Saturady" };
+
+static char *ABB_MONTH[12] = { "Jan", "Feb", "Mar", "Apr", "May", "Jun",
+							   "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" };
+
+static char *FULL_MONTH[12] = {
+	"January", "Feburary", "March",		"April",   "May",	   "June",
+	"July",	   "August",   "September", "October", "November", "December"
+};
+
+static char *write_num(unsigned int num, unsigned int pad, char *buf, size_t n)
+{
+	size_t digits = 1;
+	unsigned int x = num;
+
+	while (x /= 10, x > 0)
+		digits++;
+	if (pad == 0)
+		pad = digits;
+
+	for (size_t i = 0; i < pad; i++) {
+		size_t digit;
+		if (i >= digits) {
+			digit = 0;
+		} else {
+			digit = num % 10;
+			num /= 10;
+		}
+
+		if (pad - i - 1 >= n)
+			continue;
+		buf[pad - i - 1] = '0' + digit;
+	}
+
+	if (pad > n)
+		pad = n;
+
+	return buf + pad;
+}
+
+void timetostr(time_t *time, char *format, char *buf, size_t n)
+{
+	char *index = buf;
+	char c;
+	int space;
+
+	while (c = *format++, space = (buf + n) - index, c != '\0' && space > 0) {
+		if (c != '%') {
+			*index++ = c;
+			continue;
+		} else {
+			c = *format++;
+		}
+
+		switch (c) {
+		case '%':
+			*index++ = '%';
+			break;
+		case 'a':
+			index = strncpy(index, ABB_WEEKDAY[time->wday], space);
+			break;
+		case 'A':
+			index = strncpy(index, FULL_WEEKDAY[time->wday], space);
+			break;
+		case 'b':
+		case 'h':
+			index = strncpy(index, ABB_MONTH[time->mon], space);
+			break;
+		case 'B':
+			index = strncpy(index, FULL_MONTH[time->mon], space);
+			break;
+		case 'C':
+			index = write_num(time->cen, 0, index, space);
+			break;
+		case 'd':
+			index = write_num(time->mday, 2, index, space);
+			break;
+		case 'H':
+			index = write_num(time->hour, 2, index, space);
+			break;
+		case 'I':
+			index = write_num((time->hour + 12) % 12 + 1, 2, index, space);
+			break;
+		case 'j':
+			index = write_num(time->yday, 3, index, space);
+			break;
+		case 'm':
+			index = write_num(time->mon + 1, 2, index, space);
+			break;
+		case 'M':
+			index = write_num(time->min, 2, index, space);
+			break;
+		case 'n':
+			*index++ = '\n';
+			break;
+		case 'p':
+			index = strncpy(index, time->hour > 11 ? "PM" : "AM", space);
+			break;
+		case 'P':
+			index = strncpy(index, time->hour > 11 ? "pm" : "am", space);
+			break;
+		case 'q':
+			index = write_num((time->mon + 3) / 3, 0, index, space);
+			break;
+		case 'S':
+			index = write_num(time->sec, 2, index, space);
+			break;
+		case 't':
+			*index++ = '\t';
+			break;
+		case 'u':
+			index = write_num(((time->wday + 1) % 7) + 1, 0, index, space);
+			break;
+		case 'w':
+			index = write_num(time->wday, 0, index, space);
+			break;
+		case 'y':
+			index = write_num(time->yn, 2, index, space);
+			break;
+		case 'Y':
+			index = write_num(time->year + 1900, 0, index, space);
+			break;
+		default: {
+			char b[3] = { '%', c, '\0' };
+			index = strncpy(index, b, space);
+			break;
+		}
+		}
+	}
+
+	if (space < 1)
+		buf[n - 1] = '\0';
+	else
+		*index = '\0';
+}