Move EnsureCapacity to its own file

src/LinkDotNet.StringBuilder/ValueStringBuilder.EnsureCapacity.cs

@@ -0,0 +1,57 @@
+using System.Buffers;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace LinkDotNet.StringBuilder;
+
+public ref partial struct ValueStringBuilder
+{
+    /// <summary>
+    /// Ensures the builder's buffer size is at least <paramref name="newCapacity"/>, renting a larger buffer if not.
+    /// </summary>
+    /// <param name="newCapacity">New capacity for the builder.</param>
+    /// <remarks>
+    /// If <see cref="Length"/> is already &gt;= <paramref name="newCapacity"/>, nothing is done.
+    /// </remarks>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public void EnsureCapacity(int newCapacity)
+    {
+        if (Length >= newCapacity)
+        {
+            return;
+        }
+
+        var newSize = FindSmallestPowerOf2Above(newCapacity);
+
+        var rented = ArrayPool<char>.Shared.Rent(newSize);
+
+        if (bufferPosition > 0)
+        {
+            ref var sourceRef = ref MemoryMarshal.GetReference(buffer);
+            ref var destinationRef = ref MemoryMarshal.GetReference(rented.AsSpan());
+
+            Unsafe.CopyBlock(
+                ref Unsafe.As<char, byte>(ref destinationRef),
+                ref Unsafe.As<char, byte>(ref sourceRef),
+                (uint)bufferPosition * sizeof(char));
+        }
+
+        if (arrayFromPool is not null)
+        {
+            ArrayPool<char>.Shared.Return(arrayFromPool);
+        }
+
+        buffer = rented;
+        arrayFromPool = rented;
+    }
+
+    /// <summary>
+    /// Finds the smallest power of 2 which is greater than or equal to <paramref name="minimum"/>.
+    /// </summary>
+    /// <param name="minimum">The value the result should be greater than or equal to.</param>
+    /// <returns>The smallest power of 2 >= <paramref name="minimum"/>.</returns>
+    private static int FindSmallestPowerOf2Above(int minimum)
+    {
+        return 1 << (int)Math.Ceiling(Math.Log2(minimum));
+    }
+}

src/LinkDotNet.StringBuilder/ValueStringBuilder.cs

@@ -167,45 +167,6 @@ public readonly string ToString(Range range)
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public void Clear() => bufferPosition = 0;
 
-    /// <summary>
-    /// Ensures the builder's buffer size is at least <paramref name="newCapacity"/>, renting a larger buffer if not.
-    /// </summary>
-    /// <param name="newCapacity">New capacity for the builder.</param>
-    /// <remarks>
-    /// If <see cref="Length"/> is already &gt;= <paramref name="newCapacity"/>, nothing is done.
-    /// </remarks>
-    [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public void EnsureCapacity(int newCapacity)
-    {
-        if (Length >= newCapacity)
-        {
-            return;
-        }
-
-        int newSize = FindSmallestPowerOf2Above(newCapacity);
-
-        char[] rented = ArrayPool<char>.Shared.Rent(newSize);
-
-        if (bufferPosition > 0)
-        {
-            ref char sourceRef = ref MemoryMarshal.GetReference(buffer);
-            ref char destinationRef = ref MemoryMarshal.GetReference(rented.AsSpan());
-
-            Unsafe.CopyBlock(
-                ref Unsafe.As<char, byte>(ref destinationRef),
-                ref Unsafe.As<char, byte>(ref sourceRef),
-                (uint)bufferPosition * sizeof(char));
-        }
-
-        if (arrayFromPool is not null)
-        {
-            ArrayPool<char>.Shared.Return(arrayFromPool);
-        }
-
-        buffer = rented;
-        arrayFromPool = rented;
-    }
-
     /// <summary>
     /// Removes a range of characters from this builder.
     /// </summary>