diff --git a/libc/Makefile b/libc/Makefile
index def7844d..bc6aeb50 100644
--- a/libc/Makefile
+++ b/libc/Makefile
@@ -121,6 +121,7 @@ strtok.o \
strtok_r.o \
strxfrm.o \
timespec.o \
+time/strftime.o \
ungetc.o \
vfscanf.o \
vsscanf.o \
diff --git a/libc/sortix/time/.gitignore b/libc/sortix/time/.gitignore
new file mode 100644
index 00000000..e69de29b
diff --git a/libc/time/strftime.cpp b/libc/time/strftime.cpp
new file mode 100644
index 00000000..e08f2563
--- /dev/null
+++ b/libc/time/strftime.cpp
@@ -0,0 +1,285 @@
+/*******************************************************************************
+
+ Copyright(C) Jonas 'Sortie' Termansen 2013.
+
+ This file is part of the Sortix C Library.
+
+ The Sortix C Library is free software: you can redistribute it and/or modify
+ it under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or (at your
+ option) any later version.
+
+ The Sortix C Library is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
+ License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with the Sortix C Library. If not, see .
+
+ time/strftime.cpp
+ Format time and date into a string.
+
+*******************************************************************************/
+
+#include
+#include
+#include
+
+static const char* GetWeekdayAbbreviated(const struct tm* tm)
+{
+ switch ( tm->tm_wday % 7 )
+ {
+ case 0: return "Sun";
+ case 1: return "Mon";
+ case 2: return "Tue";
+ case 3: return "Wed";
+ case 4: return "Thu";
+ case 5: return "Fri";
+ case 6: return "Sat";
+ default: __builtin_unreachable();
+ }
+}
+
+static const char* GetWeekday(const struct tm* tm)
+{
+ switch ( tm->tm_wday % 7 )
+ {
+ case 0: return "Sunday";
+ case 1: return "Monday";
+ case 2: return "Tuesday";
+ case 3: return "Wednesday";
+ case 4: return "Thursday";
+ case 5: return "Friday";
+ case 6: return "Saturday";
+ default: __builtin_unreachable();
+ }
+}
+
+static const char* GetMonthAbbreviated(const struct tm* tm)
+{
+ switch ( tm->tm_mon % 12 )
+ {
+ case 0: return "Jan";
+ case 1: return "Feb";
+ case 2: return "Mar";
+ case 3: return "Apr";
+ case 4: return "May";
+ case 5: return "Jun";
+ case 6: return "Jul";
+ case 7: return "Aug";
+ case 8: return "Sep";
+ case 9: return "Oct";
+ case 10: return "Nov";
+ case 11: return "Dec";
+ default: __builtin_unreachable();
+ }
+}
+
+static const char* GetMonth(const struct tm* tm)
+{
+ switch ( tm->tm_mon % 12 )
+ {
+ case 0: return "January";
+ case 1: return "February";
+ case 2: return "March";
+ case 3: return "April";
+ case 4: return "May";
+ case 5: return "June";
+ case 6: return "July";
+ case 7: return "August";
+ case 8: return "Sepember";
+ case 9: return "October";
+ case 10: return "November";
+ case 11: return "December";
+ default: __builtin_unreachable();
+ }
+}
+
+extern "C"
+size_t strftime(char* s, size_t max, const char* format, const struct tm* tm)
+{
+ const char* orig_format = format;
+ size_t ret = 0;
+
+#define OUTPUT_CHAR(expr) \
+ do { \
+ if ( ret == max ) \
+ return errno = ERANGE, 0; \
+ s[ret++] = expr; \
+ } while ( 0 )
+
+#define OUTPUT_STRING(expr) \
+ do { \
+ const char* out_str = expr; \
+ while ( *out_str ) \
+ OUTPUT_CHAR(*out_str++); \
+ } while ( 0 )
+
+#define OUTPUT_STRFTIME(expr) \
+ do { \
+ int old_errno = errno; \
+ errno = 0; \
+ size_t subret = strftime(s + ret, max - ret, expr, tm); \
+ if ( !subret && errno ) \
+ return 0; \
+ errno = old_errno; \
+ ret += subret; \
+ } while ( 0 )
+
+#define OUTPUT_INT_PADDED(valexpr, widthexpr, padexpr) \
+ do { \
+ int val = valexpr; \
+ size_t width = widthexpr; \
+ char pad = padexpr; \
+ char str[sizeof(int) * 3]; str[0] = '\0'; \
+ size_t got = (size_t) snprintf(str, sizeof(str), "%i", val); \
+ while ( pad && got < width-- ) \
+ OUTPUT_CHAR(pad); \
+ OUTPUT_STRING(str); \
+ } while ( 0 )
+
+#define OUTPUT_INT(valexpr) OUTPUT_INT_PADDED(valexpr, 0,'\0')
+
+#define OUTPUT_UNSUPPORTED() \
+ do { \
+ fprintf(stderr, "%s:%u: strftime: error: unsupported format string \"%s\" around \"%%%s\"\n", \
+ __FILE__, __LINE__, orig_format, specifiers_begun_at); \
+ return 0; \
+ } while ( 0 )
+
+#define OUTPUT_UNDEFINED() OUTPUT_UNSUPPORTED()
+
+ while ( char c = *format++ )
+ {
+ if ( c != '%' )
+ {
+ OUTPUT_CHAR(c);
+ continue;
+ }
+ const char* specifiers_begun_at = format;
+ c = *format++;
+
+ // Process any optional flags.
+ char padding_char = ' ';
+ bool plus_padding = false;
+ while ( true )
+ {
+ switch ( c )
+ {
+ case '0': padding_char = '0'; break;
+ case '+': padding_char = '0'; plus_padding = true; break;
+ default: goto end_of_flags;
+ }
+ c = *format++;
+ }
+ end_of_flags:
+
+ // TODO: Support the '+' flag!
+ if ( plus_padding )
+ OUTPUT_UNSUPPORTED();
+
+ // Process the optional minimum field width.
+ size_t field_width = 0;
+ while ( '0' <= c && c <= '9' )
+ field_width = field_width * 10 + c - '0',
+ c = *format++;
+
+ // Process an optional E or O modifier.
+ bool e_modifier = false;
+ bool o_modifier = false;
+ if ( c == 'E' )
+ e_modifier = true,
+ c = *format++;
+ else if ( c == 'O' )
+ o_modifier = true,
+ c = *format++;
+
+ // TODO: Support the E and O modifiers where marked with the E and O
+ // comments in the below switch.
+ if ( e_modifier || o_modifier ) { }
+
+ switch ( c )
+ {
+ case 'a': OUTPUT_STRING(GetWeekdayAbbreviated(tm)); break;
+ case 'A': OUTPUT_STRING(GetWeekday(tm)); break;
+ case 'b': OUTPUT_STRING(GetMonthAbbreviated(tm)); break;
+ case 'B': OUTPUT_STRING(GetMonth(tm)); break;
+ case 'c': /*E*/
+ OUTPUT_STRING(GetWeekday(tm));
+ OUTPUT_STRING(" ");
+ OUTPUT_STRING(GetMonthAbbreviated(tm));
+ OUTPUT_STRING(" ");
+ OUTPUT_INT_PADDED(tm->tm_mday, 2, '0');
+ OUTPUT_STRING(" ");
+ OUTPUT_INT_PADDED(tm->tm_hour, 2, '0');
+ OUTPUT_STRING(":");
+ OUTPUT_INT_PADDED(tm->tm_min, 2, '0');
+ OUTPUT_STRING(":");
+ OUTPUT_INT_PADDED(tm->tm_sec, 2, '0');
+ break;
+ case 'C': /*E*/
+ if ( !field_width )
+ field_width = 2;
+ OUTPUT_INT_PADDED((tm->tm_year + 1900) / 100, field_width, padding_char);
+ break;
+ case 'd': OUTPUT_INT_PADDED(tm->tm_mday, 2, '0'); break; /*O*/
+ case 'D': OUTPUT_STRFTIME("%m/%d/%y"); break;
+ case 'e': OUTPUT_INT_PADDED(tm->tm_mday, 2, ' '); break; /*O*/
+ case 'F':
+ // TODO: Revisit this.
+ OUTPUT_UNSUPPORTED();
+ break;
+ case 'g':
+ // TODO: These require a bit of intelligence.
+ OUTPUT_UNSUPPORTED();
+ break;
+ case 'G':
+ // TODO: These require a bit of intelligence.
+ OUTPUT_UNSUPPORTED();
+ break;
+ case 'h': OUTPUT_STRFTIME("%b"); break;
+ case 'H': OUTPUT_INT_PADDED(tm->tm_hour, 2, '0'); break; /*O*/
+ case 'I': OUTPUT_INT_PADDED(tm->tm_hour % 12 + 1, 2, '0'); break; /*O*/
+ case 'j': OUTPUT_INT_PADDED(tm->tm_yday + 1, 3, '0'); break;
+ case 'm': OUTPUT_INT_PADDED(tm->tm_mon + 1, 2, '0'); break; /*O*/
+ case 'M': OUTPUT_INT_PADDED(tm->tm_min, 2, '0'); break; /*O*/
+ case 'n': OUTPUT_CHAR('\n'); break;
+ case 'p': OUTPUT_STRING(tm->tm_hour < 12 ? "AM" : "PM"); break;
+ case 'r': OUTPUT_STRFTIME("%I:%M:%S %p"); break;
+ case 'R': OUTPUT_STRFTIME("%H:%M"); break;
+ case 'S': OUTPUT_INT_PADDED(tm->tm_sec, 2, '0'); break; /*O*/
+ case 't': OUTPUT_CHAR('\t'); break;
+ case 'T': OUTPUT_STRFTIME("H:%M:%S"); break;
+ case 'u': OUTPUT_INT(tm->tm_yday); break; /*O*/
+ case 'U': /*O*/
+ // TODO: These require a bit of intelligence.
+ OUTPUT_UNSUPPORTED();
+ break;
+ case 'V': /*O*/
+ // TODO: These require a bit of intelligence.
+ OUTPUT_UNSUPPORTED();
+ break;
+ case 'w': OUTPUT_INT(tm->tm_wday); break; /*O*/
+ case 'W': /*O*/
+ // TODO: These require a bit of intelligence.
+ OUTPUT_UNSUPPORTED();
+ break;
+ case 'x': OUTPUT_STRFTIME("%m/%d/%y"); break; /*E*/
+ case 'X': OUTPUT_STRFTIME("%H:%M:%S"); break; /*E*/
+ case 'y': OUTPUT_INT_PADDED((tm->tm_year + 1900) % 100, 2, '0'); break; /*EO*/
+ case 'Y': OUTPUT_INT(tm->tm_year + 1900); break; /*E*/
+ case 'z':
+ // TODO: struct tm doesn't have all this information available!
+ break;
+ case 'Z':
+ // TODO: struct tm doesn't have all this information available!
+ break;
+ case '%': OUTPUT_CHAR('%'); break;
+ default: OUTPUT_UNDEFINED(); break;
+ }
+ }
+ if ( ret == max )
+ return errno = ERANGE, 0;
+ return s[ret] = '\0', ret;
+}