A bit of work on time, but it doesn't actually work yet.

src/time/time.c

@@ -0,0 +1,98 @@
+/*
+ * time.h
+ *
+ * Bare bones of PSSE time. See issue #16.
+ *
+ * (c) 2019 Simon Brooke <simon@journeyman.cc>
+ * Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#include <stdlib.h>
+#include <time.h>
+/*
+ * wide characters
+ */
+#include <wchar.h>
+#include <wctype.h>
+
+#include "conspage.h"
+#include "consspaceobject.h"
+#include "integer.h"
+#include "time.h"
+#define _GNU_SOURCE
+
+#define seconds_per_year 31557600L
+
+/**
+ * PSSE Lisp epoch is 14 Bn years, or 441,806,400,000,000,000 seconds, before
+ * the UNIX epoch; the value in microseconds will break the C reader.
+ */
+unsigned __int128 epoch_offset = ((__int128)(seconds_per_year * 1000000000L) *
+                                  (__int128)(14L * 1000000000L));
+
+/**
+ * Return the UNIX time value which represents this time, if it falls within
+ * the period representable in UNIX time, or zero otherwise.
+ */
+long int lisp_time_to_unix_time(struct cons_pointer t) {
+    long int result = 0;
+
+    if (timep( t)) {
+        unsigned __int128 value = pointer2cell(t).payload.time.value;
+
+        if (value > epoch_offset) { // \todo && value < UNIX time rollover
+            result = ((value - epoch_offset) / 1000000000);
+        }
+    }
+
+    return result;
+}
+
+unsigned __int128 unix_time_to_lisp_time( time_t t) {
+    unsigned __int128 result = epoch_offset + (t * 1000000000);
+
+    return result;
+}
+
+struct cons_pointer make_time( struct cons_pointer integer_or_nil) {
+    struct cons_pointer pointer = allocate_cell( TIMETAG );
+    struct cons_space_object *cell = &pointer2cell( pointer );
+
+    if (integerp(integer_or_nil)) {
+        cell->payload.time.value = pointer2cell(integer_or_nil).payload.integer.value;
+        // \todo: if integer is a bignum, deal with it.
+    } else {
+        cell->payload.time.value = unix_time_to_lisp_time( time(NULL));
+    }
+
+    return pointer;
+}
+
+/**
+ * Function; return a time representation of the first argument in the frame;
+ * further arguments are ignored.
+ *
+ * * (time integer_or_nil)
+ *
+ * @param frame my stack_frame.
+ * @param frame_pointer a pointer to my stack_frame.
+ * @param env my environment.
+ * @return a lisp time; if `integer_or_nil` is an integer, return a time which
+ * is that number of microseconds after the notional big bang; else the current
+ * time.
+ */
+struct cons_pointer lisp_time( struct stack_frame *frame, struct cons_pointer frame_pointer,
+           struct cons_pointer env ) {
+    return make_time( frame->arg[0]);
+}
+
+/**
+ * This is temporary, for bootstrapping.
+ */
+struct cons_pointer time_to_string( struct cons_pointer pointer) {
+    long int t = lisp_time_to_unix_time(pointer);
+
+    return c_string_to_lisp_string( t == 0 ?
+                                         L"Not yet implemented: cannot print times outside UNIX time\n" :
+                                         ctime(&t));
+}

src/time/time.h

@@ -0,0 +1,20 @@
+/*
+ * time.h
+ *
+ * Bare bones of PSSE time. See issue #16.
+ *
+ * (c) 2019 Simon Brooke <simon@journeyman.cc>
+ * Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#ifndef __psse_time_h
+#define __psse_time_h
+
+#define _GNU_SOURCE
+#include "consspaceobject.h"
+
+struct cons_pointer lisp_time( struct stack_frame *frame, struct cons_pointer frame_pointer,
+           struct cons_pointer env );
+struct cons_pointer time_to_string( struct cons_pointer pointer);
+
+#endif