Port ValueStringBuilder updates/fixes from corefx

Author: stephentoub

src/mscorlib/shared/System/Number.Formatting.cs

@@ -306,7 +306,7 @@ public static string FormatDecimal(decimal value, ReadOnlySpan<char> format, Num
                 NumberToStringFormat(ref sb, ref number, format, info);
             }
 
-            return sb.GetString();
+            return sb.ToString();
         }
 
         public static bool TryFormatDecimal(decimal value, ReadOnlySpan<char> format, NumberFormatInfo info, Span<char> destination, out int charsWritten)
@@ -405,7 +405,7 @@ public static string FormatDouble(double value, string format, NumberFormatInfo
                             NumberToString(ref sb, ref number, 'G', 17, info, isDecimal: false);
                         }
 
-                        return sb.GetString();
+                        return sb.ToString();
                     }
 
                 case 'E':
@@ -446,7 +446,7 @@ public static string FormatDouble(double value, string format, NumberFormatInfo
                 NumberToStringFormat(ref sb, ref number, format, info);
             }
 
-            return sb.GetString();
+            return sb.ToString();
         }
 
         public static string FormatSingle(float value, string format, NumberFormatInfo info)
@@ -490,7 +490,7 @@ public static string FormatSingle(float value, string format, NumberFormatInfo i
                             NumberToString(ref sb, ref number, 'G', 9, info, isDecimal: false);
                         }
 
-                        return sb.GetString();
+                        return sb.ToString();
                     }
 
                 case 'E':
@@ -531,7 +531,7 @@ public static string FormatSingle(float value, string format, NumberFormatInfo i
                 NumberToStringFormat(ref sb, ref number, format, info);
             }
 
-            return sb.GetString();
+            return sb.ToString();
         }
 
         public static string FormatInt32(int value, ReadOnlySpan<char> format, NumberFormatInfo info)
@@ -570,7 +570,7 @@ public static string FormatInt32(int value, ReadOnlySpan<char> format, NumberFor
                 {
                     NumberToStringFormat(ref sb, ref number, format, info);
                 }
-                return sb.GetString();
+                return sb.ToString();
             }
         }
 
@@ -648,7 +648,7 @@ public static string FormatUInt32(uint value, ReadOnlySpan<char> format, NumberF
                 {
                     NumberToStringFormat(ref sb, ref number, format, info);
                 }
-                return sb.GetString();
+                return sb.ToString();
             }
         }
 
@@ -727,7 +727,7 @@ public static string FormatInt64(long value, ReadOnlySpan<char> format, NumberFo
                 {
                     NumberToStringFormat(ref sb, ref number, format, info);
                 }
-                return sb.GetString();
+                return sb.ToString();
             }
         }
 
@@ -807,7 +807,7 @@ public static string FormatUInt64(ulong value, ReadOnlySpan<char> format, Number
                 {
                     NumberToStringFormat(ref sb, ref number, format, info);
                 }
-                return sb.GetString();
+                return sb.ToString();
             }
         }
 

src/mscorlib/shared/System/Text/ValueStringBuilder.cs

@@ -21,42 +21,42 @@ public ValueStringBuilder(Span<char> initialBuffer)
             _pos = 0;
         }
 
-        public string GetString()
+        public int Length => _pos;
+
+        public override string ToString()
         {
             var s = new string(_chars.Slice(0, _pos));
-
-            char[] toReturn = _arrayToReturnToPool;
-            this = default; // for safety, to avoid using pooled array if this instance is erroneously appended to again
-
-            if (toReturn != null)
-            {
-                ArrayPool<char>.Shared.Return(toReturn);
-            }
-
+            Clear();
             return s;
         }
 
         public bool TryCopyTo(Span<char> destination, out int charsWritten)
         {
-            if (_pos > destination.Length)
+            if (_chars.Slice(0, _pos).TryCopyTo(destination))
+            {
+                charsWritten = _pos;
+                Clear();
+                return true;
+            }
+            else
             {
                 charsWritten = 0;
+                Clear();
                 return false;
             }
+        }
 
-            bool copied = _chars.Slice(0, _pos).TryCopyTo(destination);
-            Debug.Assert(copied);
-            charsWritten = _pos;
-
-            char[] toReturn = _arrayToReturnToPool;
-            this = default; // for safety, to avoid using pooled array if this instance is erroneously appended to again
-
-            if (toReturn != null)
+        public void Insert(int index, char value, int count)
+        {
+            if (_pos > _chars.Length - count)
             {
-                ArrayPool<char>.Shared.Return(toReturn);
+                Grow(count);
             }
 
-            return true;
+            int remaining = _pos - index;
+            _chars.Slice(index, remaining).CopyTo(_chars.Slice(index + count));
+            _chars.Slice(index, count).Fill(value);
+            _pos += count;
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -158,7 +158,7 @@ private void Grow(int requiredAdditionalCapacity)
         {
             Debug.Assert(requiredAdditionalCapacity > _chars.Length - _pos);
 
-            char[] poolArray = ArrayPool<char>.Shared.Rent(_pos + requiredAdditionalCapacity);
+            char[] poolArray = ArrayPool<char>.Shared.Rent(Math.Max(_pos + requiredAdditionalCapacity, _chars.Length * 2));
 
             bool success = _chars.TryCopyTo(poolArray);
             Debug.Assert(success);
@@ -170,5 +170,16 @@ private void Grow(int requiredAdditionalCapacity)
                 ArrayPool<char>.Shared.Return(toReturn);
             }
         }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private void Clear()
+        {
+            char[] toReturn = _arrayToReturnToPool;
+            this = default; // for safety, to avoid using pooled array if this instance is erroneously appended to again
+            if (toReturn != null)
+            {
+                ArrayPool<char>.Shared.Return(toReturn);
+            }
+        }
     }
 }