revamping datetime draft

README.md

@@ -142,12 +142,27 @@ ID    |Params           |Command|Meaning
 `03`  |1s 3b [addr addr]|`a3`   |Read a byte under the 3-byte flash address
 `04`  |1b 3b [page addr]|`84`   |Write a page under the 3-byte flash address
 `05`  |1b 3b [page addr]|`85`   |Read a page under the 3-byte flash address
-`06`  |1s [addr]        |`46`   |Read the current system time/date information (5 bytes/40 bits, Unix time) into the address
-`07`  |1s [addr]        |`47`   |Set the current system time/date information (5 bytes/40 bits, Unix time) from the address
+`06`  |1s [addr]        |`46`   |Read the current system time/date information (see below) into the address
+`07`  |1s [addr]        |`47`   |Set the current system time/date information (see below) from the address
 `08-1d`|                |       |(reserved)
 `1e`  |1b 3b [flag addr]|`9e`   |Load and run another Uxn/ESOP application from flash address according to the flags
 `1f`  |None             |`1f`   |Halt (required)
 
+### Datetime syscall implementation notes
+
+The `46` and `47` calls, where implemented, should operate on 10 bytes of memory addressed by the value passed to them.
+The layout of these 10 bytes is similar to the one defined in Uxn/Varvara and Uxn/SPARTA specs:
+
+- `00-01`: year
+- `02`: month
+- `03`: day
+- `04`: hour
+- `05`: minute
+- `06`: second
+- `07`: day of the week
+- `08-09`: day of the year
+- `0a`: DST flag for the local time
+
 ## Credits
 
 Spec and reference implementation developed by Luxferre in 2022, released into the public domain.

web/esop-ext.js

@@ -172,19 +172,48 @@ function ESOPExtensions() {
 
   //syscalls
 
+  //thanks to Toastrackenigma for the idea
+  function isDST(d, y) {
+    var jan = new Date(y, 0, 1).getTimezoneOffset(),
+        jul = new Date(y, 6, 1).getTimezoneOffset()
+    return Math.max(jan, jul) !== d.getTimezoneOffset() 
+  }
+  //thanks to user2501097 for the idea
+  function daysIntoYear(y, m, d) {
+    return (Date.UTC(y, m, d) - Date.UTC(y, 0, 0)) / 86400000
+  }
+
+  function fillDTbuf(addr) {
+    var now = new Date(),
+        year = now.getFullYear(),
+        month = now.getMonth() + 1,
+        day = now.getDate(),
+        hour = now.getHours(),
+        minute = now.getMinutes(),
+        second = now.getSeconds(),
+        dotw = now.getDay(),
+        doty = daysIntoYear(year, month - 1, day),
+        dstflag = 0|isDST(now, year)
+    vm.setram(addr, year >> 8)
+    vm.setram(addr+1, year&255)
+    vm.setram(addr+2, month)
+    vm.setram(addr+3, day)
+    vm.setram(addr+4, hour)
+    vm.setram(addr+5, minute)
+    vm.setram(addr+6, second)
+    vm.setram(addr+7, dotw)
+    vm.setram(addr+8, doty >> 8)
+    vm.setram(addr+9, doty&255)
+    vm.setram(addr+10, dstflag)
+
+  }
+
   function runSyscall(vm, buf) {
     var call = buf[0]
     if(call === 0x00) //simulate writing a byte to the debug port
       console.log('[DBG] ' + ('00' + buf[1].toString(16)).slice(-2))
-    else if(call === 0x06) { //read datetime info into 5 bytes starting from addr
-      //not very optimal but a future-proof approach for now
-      var tm = ('00' + (0|(Date.now()/1000)).toString(16)).slice(-10).match(/.{2}/g).map(function(x){return parseInt(x, 16)}),
-          targetaddr = (buf[1]<<8)|buf[2]
-      vm.setram(targetaddr, tm[0])
-      vm.setram(targetaddr+1, tm[1])
-      vm.setram(targetaddr+2, tm[2])
-      vm.setram(targetaddr+3, tm[3])
-      vm.setram(targetaddr+4, tm[4])
+    else if(call === 0x06) { //read datetime info into 10 bytes starting from addr
+      fillDTbuf((buf[1]<<8)|buf[2])
     }
     else if(call === 0x1f) //halt call, required for all implementations
       vm.active = false

web/esop-web-app.js

@@ -4,15 +4,13 @@ function main() {
   var devCfg = { 
     audio: null,
     canvas: document.getElementById('C') //JS-specific implementation canvas DOM reference
-  }
+  }, vm = UxnCore(), ext = ESOPExtensions()
 
   document.getElementById('apprun').addEventListener('click', function() {
     var fileObj = document.getElementById('appselect').files[0]
     if(fileObj.name.endsWith('.eso')) {
       var rdr = new FileReader()
       rdr.onload = function() {
-        var vm = UxnCore()
-        var ext = ESOPExtensions()
         devCfg.audio = new (window.AudioContext || window.webkitAudioContext)
         vm.boot()
         ext.setup(vm, devCfg)