[R] 提取出Utils.BarAndTick和Utils.Tick函数。

Author: Starrah

generator/mai/MA2Generator.cs

@@ -58,19 +58,10 @@ GENERATED_BY	MuConvert v{8}
     /**
      * 把Rational的时间近似到RESOLUTION允许的最接近tick上
      */
-    private (int, int) BT(Rational r, int offset = 0)
-    {
-        if (offset != 0) r += new Rational(offset, RSL);
-        return ((int)r.WholePart, (int)Math.Round((double)(r.FractionPart * RSL)));
-    }
+    private (int, int) BT(Rational r, int offset = 0) => Utils.BarAndTick(r, RSL, offset);
 
     // 持续时间/等待时间，使用"总tick数"（可超过1小节），不是小节内tick
-    protected int T(Rational r, int offset = 0)
-    {
-        var result = (int)Math.Round((double)(r* RSL));
-        if (offset != 0) result = Math.Max(result + offset, result > 0 ? 1 : 0);
-        return result;
-    }
+    protected int T(Rational r, int offset = 0) => Utils.Tick(r, RSL, offset, r > 0 ? 1 : 0);
     protected int T(int bar, int tick) => bar * RSL + tick;
     protected int T(MA2Line ma2Line) => T(ma2Line.Bar, ma2Line.Tick);
 

utils/Utils.cs

@@ -1,4 +1,4 @@
-using System.Globalization;
+using System.Globalization;
 using System.Numerics;
 using System.Reflection;
 using Rationals;
@@ -37,6 +37,33 @@ internal static Exception Fail(string msg = "")
     internal static int TokenType(string str) => _simaiLexerMap[str];
 
     internal static bool IsModifier(int tokenType) => tokenType is L.MODIFIER or L.TAP_TO_STAR or L.STAR_TO_TAP or L.NO_STAR;
+
+    public static (int, int) BarAndTick(Rational time, int resolution, int extraTicks = 0)
+    {
+        var bar = time.WholePart;
+        var tick = (time.FractionPart * resolution).Round();
+        tick += extraTicks;
+        
+        while (tick >= resolution)
+        {
+            tick -= resolution;
+            bar++;
+        }
+        while (tick < 0)
+        {
+            tick += resolution;
+            bar--;
+        }
+
+        return ((int)bar, (int)tick);
+    }
+    
+    public static int Tick(Rational time, int resolution, int extraTicks = 0, int? min = null)
+    {
+        var r = (int)((time * resolution).Round() + extraTicks);
+        if (min != null && r < min) r = min.Value;
+        return r;
+    }
 }
 
 internal static class ExtensionUtils
@@ -63,6 +90,17 @@ public static Rational Ceil(this Rational r)
         return r.WholePart + (r.FractionPart == 0 ? 0 : 1);
     }
 
+    private static readonly Rational _half = new(1, 2);
+    // 工作范围仅限非负数；舍入策略方面，使用与系统库Math.Round相同的“四舍六入五成双”算法。
+    public static BigInteger Round(this Rational r)
+    {
+        if (r < 0) throw new ArgumentOutOfRangeException(nameof(r));
+        var whole = r.WholePart;
+        var frac = r.FractionPart;
+        var shouldAdd = frac > _half || (frac == _half && whole % 2 == 1);
+        return whole + (shouldAdd ? 1 : 0);
+    }
+    
     public static Rational Sum(this IEnumerable<Rational> source)
     {
         return source.Aggregate(Rational.Zero, (acc, r) => acc + r);