From b1cf9e5dfbc8967bd7cb2a22ec1e5e521f4e0e6e Mon Sep 17 00:00:00 2001
From: Benji Dial <benji@benjidial.net>
Date: Wed, 31 Jul 2024 13:36:53 -0400
Subject: add clock

---
 euler/source/std/ctime.cpp | 58 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 euler/source/std/ctime.cpp

(limited to 'euler/source/std')

diff --git a/euler/source/std/ctime.cpp b/euler/source/std/ctime.cpp
new file mode 100644
index 0000000..d83817a
--- /dev/null
+++ b/euler/source/std/ctime.cpp
@@ -0,0 +1,58 @@
+#include <euler/syscall.hpp>
+#include <ctime>
+
+time_t time(time_t *arg) {
+  time_t t = euler::syscall::get_time();
+  if (arg) *arg = t;
+  return t;
+}
+
+static tm static_tm;
+
+static int days_per_month[] = {
+  31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31,
+  31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31,
+  31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31,
+  31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
+};
+
+tm *gmtime(const time_t *time) {
+
+  time_t t = *time / 1024;
+
+  static_tm.tm_isdst = 0;
+
+  static_tm.tm_sec  = t % 60; t /= 60;
+  static_tm.tm_min  = t % 60; t /= 60;
+  static_tm.tm_hour = t % 24; t /= 24;
+  static_tm.tm_wday = (t + 5) % 7 + 1;
+  static_tm.tm_year = (t / 1461) * 4 + 100;
+
+  int days_into_quadyear = t % 1461;
+
+  static_tm.tm_yday = 0;
+  static_tm.tm_mon = 0;
+  static_tm.tm_mday = 1;
+
+  for (int i = 0; i < 48; ++i) {
+    if (days_into_quadyear >= days_per_month[i]) {
+      days_into_quadyear -= days_per_month[i];
+      if (static_tm.tm_mon == 11) {
+        static_tm.tm_mon = 0;
+        static_tm.tm_yday = 0;
+      }
+      else {
+        ++static_tm.tm_mon;
+        static_tm.tm_yday += days_per_month[i];
+      }
+    }
+    else {
+      static_tm.tm_yday += days_into_quadyear;
+      static_tm.tm_mday += days_into_quadyear;
+      break;
+    }
+  }
+
+  return &static_tm;
+
+}
-- 
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