Chapter 31: Software Drawing, Time, and Graphical Gameslinear

Co-authored-by: Hsiang-Ying Fu <66062782+fuhsnn@users.noreply.github.com>
Co-authored-by: fuhsnn <66062782+fuhsnn@users.noreply.github.com>
Co-authored-by: Symious <14933944+symious@users.noreply.github.com>
Co-authored-by: Jun Kawasaki <jun784@gmail.com>
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 80 insertions, 0 deletions

diff --git a/src/main/smp/sys/time/Timers.smp b/src/main/smp/sys/time/Timers.smp
new file mode 100644
index 00000000..eca32d15
--- /dev/null
+++ b/src/main/smp/sys/time/Timers.smp
@@ -0,0 +1,80 @@
+// Cooperative timers. poll returns IDs; callbacks never run on another thread.
+// IDs are u32; 0 means failure or no timer due. Millisecond values use _ms.
+
+// The
+
+
+struct Timers {
+    // Collection of timers (as struct-of-arrays)
+    u32[] !_ids       = new u32[8]; // Which timer id for this slot
+    i64[] !_due_ms    = new i64[8]; // Monotonic deadline in milliseconds
+    i64[] !_period_ms = new i64[8]; // When does it repeat
+    // Next available timer ID; 0 means all IDs have been used.
+    u32 !_next = 1;
+
+    // Add a new timer
+    { i64 i64 i64 -> u32 } _add = { i64 current_ms, i64 delay_ms, i64 period_ms ->
+        if( current_ms<0 || delay_ms<0 || current_ms>sys.integer.MAX_I64-delay_ms || _next==0 ) return 0;
+        // Ugly linear scan for an available slot
+        int slot=0;
+        while( slot<_ids# && _ids[slot]!=0 ) slot++;
+        // Double size for lots of timers
+        if( slot==_ids# ) {
+            if( _ids#>sys.integer.MAX_I32/2 ) return 0;
+            val ids = new u32[_ids#*2];
+            val due_ms = new i64[_ids#*2], periods_ms = new i64[_ids#*2];
+            for( int i=0; i<_ids#; i++ ) { ids[i]=_ids[i]; due_ms[i]=_due_ms[i]; periods_ms[i]=_period_ms[i]; }
+            _ids=ids; _due_ms=due_ms; _period_ms=periods_ms;
+            // Retry against the newly published arrays after growing.
+            return _add(current_ms,delay_ms,period_ms);
+        }
+        // Next available timer id
+        u32 id = _next;
+        _next = id==sys.integer.MAX_U32 ? 0 : id+1;
+        _ids[slot]=id; _due_ms[slot]=current_ms+delay_ms; _period_ms[slot]=period_ms;
+        return id;
+    };
+
+    // Explicit-clock versions make game logic and tests deterministic.
+    { i64 i64 -> u32 } afterAt = { i64 current_ms, i64 delay_ms -> _add(current_ms,delay_ms,0); };
+    { i64 i64 -> u32 } everyAt = { i64 current_ms, i64 period_ms -> period_ms<=0 ? 0 : _add(current_ms,period_ms,period_ms); };
+    { i64 -> u32 } after = { i64 delay_ms  -> afterAt(time.monotonic(),delay_ms ); };
+    { i64 -> u32 } every = { i64 period_ms -> everyAt(time.monotonic(),period_ms); };
+
+    // Remove a timer
+    val cancel = { u32 id ->
+        if( id==0 ) return false;
+        for( int i=0; i<_ids#; i++ ) if( _ids[i]==id ) { _ids[i]=0; return true; }
+        return false;
+    };
+
+    // Earliest absolute monotonic deadline in milliseconds, or -1 when empty.
+    val nextDeadline = { ->
+        i64 next_ms = -1;
+        // Ugly linear scan again, but short
+        for( int i=0; i<_ids#; i++ )
+            if( _ids[i]!=0 && (next_ms<0 || _due_ms[i] < next_ms) ) next_ms = _due_ms[i];
+        return next_ms;
+    };
+
+    // Next firing timer.
+
+    // Earliest deadline first; equal deadlines use registration order.
+    // Repeats skip missed ticks and retain their phase, avoiding bursts/drift.
+    { i64 -> u32 } poll = { i64 current_ms ->
+        int slot = -1;
+        for( int i=0; i<_ids#; i++ )
+            if( _ids[i]!=0 && _due_ms[i]<=current_ms && (slot<0 || _due_ms[i]<_due_ms[slot] ||
+                (_due_ms[i]==_due_ms[slot] && _ids[i]<_ids[slot])) ) slot=i;
+        if( slot<0 ) return 0;
+        u32 id = _ids[slot];
+        i64 period_ms = _period_ms[slot];
+        if( period_ms==0 ) _ids[slot]=0;
+        else {
+            i64 steps = (current_ms-_due_ms[slot])/period_ms;
+            if( steps>=(sys.integer.MAX_I64-_due_ms[slot])/period_ms ) _ids[slot]=0;
+            else _due_ms[slot] += (steps+1)*period_ms;
+        }
+        return id;
+    };
+};