Reduce allocations in StringBuilder.AppendFormat for primitive types (#15110)

justinvp · jkotas · commit b3005fe1947b · 2017-11-20T18:11:58.000-08:00
Use the new `TryFormat` APIs to avoid string allocations for primitive types
inside `StringBuilder.AppendFormat`, used by `string.Format`/interpolated
strings.
diff --git a/src/mscorlib/shared/System.Private.CoreLib.Shared.projitems b/src/mscorlib/shared/System.Private.CoreLib.Shared.projitems
@@ -211,6 +211,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)System\IObservable.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\IObserver.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\IProgress.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\ISpanFormattable.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Int16.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Int32.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Int64.cs" />
diff --git a/src/mscorlib/shared/System/Byte.cs b/src/mscorlib/shared/System/Byte.cs
@@ -12,7 +12,7 @@ namespace System
     [Serializable]
     [StructLayout(LayoutKind.Sequential)]
     [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
-    public struct Byte : IComparable, IConvertible, IFormattable, IComparable<Byte>, IEquatable<Byte>
+    public struct Byte : IComparable, IConvertible, IFormattable, IComparable<Byte>, IEquatable<Byte>, ISpanFormattable
     {
         private byte m_value; // Do not rename (binary serialization)
 
diff --git a/src/mscorlib/shared/System/DateTime.cs b/src/mscorlib/shared/System/DateTime.cs
@@ -53,7 +53,7 @@ namespace System
     [StructLayout(LayoutKind.Auto)]
     [Serializable]
     [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")] 
-    public readonly partial struct DateTime : IComparable, IFormattable, IConvertible, IComparable<DateTime>, IEquatable<DateTime>, ISerializable
+    public readonly partial struct DateTime : IComparable, IFormattable, IConvertible, IComparable<DateTime>, IEquatable<DateTime>, ISerializable, ISpanFormattable
     {
         // Number of 100ns ticks per time unit
         private const long TicksPerMillisecond = 10000;
diff --git a/src/mscorlib/shared/System/DateTimeOffset.cs b/src/mscorlib/shared/System/DateTimeOffset.cs
@@ -31,7 +31,7 @@ namespace System
     [StructLayout(LayoutKind.Auto)]
     [Serializable]
     [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")] 
-    public struct DateTimeOffset : IComparable, IFormattable, IComparable<DateTimeOffset>, IEquatable<DateTimeOffset>, ISerializable, IDeserializationCallback
+    public struct DateTimeOffset : IComparable, IFormattable, IComparable<DateTimeOffset>, IEquatable<DateTimeOffset>, ISerializable, IDeserializationCallback, ISpanFormattable
     {
         // Constants
         internal const Int64 MaxOffset = TimeSpan.TicksPerHour * 14;
diff --git a/src/mscorlib/shared/System/Guid.cs b/src/mscorlib/shared/System/Guid.cs
@@ -13,7 +13,7 @@ namespace System
     [Serializable]
     [Runtime.Versioning.NonVersionable] // This only applies to field layout
     [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
-    public partial struct Guid : IFormattable, IComparable, IComparable<Guid>, IEquatable<Guid>
+    public partial struct Guid : IFormattable, IComparable, IComparable<Guid>, IEquatable<Guid>, ISpanFormattable
     {
         public static readonly Guid Empty = new Guid();
 
@@ -1426,5 +1426,11 @@ public bool TryFormat(Span<char> destination, out int charsWritten, string forma
             charsWritten = guidSize;
             return true;
         }
+
+        bool ISpanFormattable.TryFormat(Span<char> destination, out int charsWritten, string format, IFormatProvider provider)
+        {
+            // Like with the IFormattable implementation, provider is ignored.
+            return TryFormat(destination, out charsWritten, format);
+        }
     }
 }
diff --git a/src/mscorlib/shared/System/ISpanFormattable.cs b/src/mscorlib/shared/System/ISpanFormattable.cs
@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System
+{
+    internal interface ISpanFormattable
+    {
+        bool TryFormat(Span<char> destination, out int charsWritten, string format = null, IFormatProvider provider = null);
+    }
+}
diff --git a/src/mscorlib/shared/System/Int16.cs b/src/mscorlib/shared/System/Int16.cs
@@ -12,7 +12,7 @@ namespace System
     [Serializable]
     [StructLayout(LayoutKind.Sequential)]
     [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
-    public struct Int16 : IComparable, IConvertible, IFormattable, IComparable<Int16>, IEquatable<Int16>
+    public struct Int16 : IComparable, IConvertible, IFormattable, IComparable<Int16>, IEquatable<Int16>, ISpanFormattable
     {
         private short m_value; // Do not rename (binary serialization)
 
diff --git a/src/mscorlib/shared/System/Int32.cs b/src/mscorlib/shared/System/Int32.cs
@@ -12,7 +12,7 @@ namespace System
     [Serializable]
     [StructLayout(LayoutKind.Sequential)]
     [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
-    public struct Int32 : IComparable, IConvertible, IFormattable, IComparable<Int32>, IEquatable<Int32>
+    public struct Int32 : IComparable, IConvertible, IFormattable, IComparable<Int32>, IEquatable<Int32>, ISpanFormattable
     {
         private int m_value; // Do not rename (binary serialization)
 
diff --git a/src/mscorlib/shared/System/Int64.cs b/src/mscorlib/shared/System/Int64.cs
@@ -12,7 +12,7 @@ namespace System
     [Serializable]
     [StructLayout(LayoutKind.Sequential)]
     [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
-    public struct Int64 : IComparable, IConvertible, IFormattable, IComparable<Int64>, IEquatable<Int64>
+    public struct Int64 : IComparable, IConvertible, IFormattable, IComparable<Int64>, IEquatable<Int64>, ISpanFormattable
     {
         private long m_value; // Do not rename (binary serialization)
 
diff --git a/src/mscorlib/shared/System/SByte.cs b/src/mscorlib/shared/System/SByte.cs
@@ -12,7 +12,7 @@ namespace System
     [Serializable]
     [CLSCompliant(false)]    [StructLayout(LayoutKind.Sequential)]
     [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
-    public struct SByte : IComparable, IConvertible, IFormattable, IComparable<SByte>, IEquatable<SByte>
+    public struct SByte : IComparable, IConvertible, IFormattable, IComparable<SByte>, IEquatable<SByte>, ISpanFormattable
     {
         private sbyte m_value; // Do not rename (binary serialization)
 
diff --git a/src/mscorlib/shared/System/Text/StringBuilder.cs b/src/mscorlib/shared/System/Text/StringBuilder.cs
@@ -1617,9 +1617,24 @@ internal StringBuilder AppendFormatHelper(IFormatProvider provider, String forma
 
                 if (s == null)
                 {
-                    IFormattable formattableArg = arg as IFormattable;
+                    // If arg is ISpanFormattable and the beginning doesn't need padding,
+                    // try formatting it into the remaining current chunk.
+                    if (arg is ISpanFormattable spanFormattableArg &&
+                        (leftJustify || width == 0) &&
+                        spanFormattableArg.TryFormat(RemainingCurrentChunk, out int charsWritten, itemFormat, provider))
+                    {
+                        m_ChunkLength += charsWritten;
+
+                        // Pad the end, if needed.
+                        int padding = width - charsWritten;
+                        if (leftJustify && padding > 0) Append(' ', padding);
+
+                        // Continue to parse other characters.
+                        continue;
+                    }
 
-                    if (formattableArg != null)
+                    // Otherwise, fallback to trying IFormattable or calling ToString.
+                    if (arg is IFormattable formattableArg)
                     {
                         s = formattableArg.ToString(itemFormat, provider);
                     }
diff --git a/src/mscorlib/shared/System/TimeSpan.cs b/src/mscorlib/shared/System/TimeSpan.cs
@@ -28,7 +28,7 @@ namespace System
     // an appropriate custom ILMarshaler to keep WInRT interop scenarios enabled.
     //
     [Serializable]
-    public struct TimeSpan : IComparable, IComparable<TimeSpan>, IEquatable<TimeSpan>, IFormattable
+    public struct TimeSpan : IComparable, IComparable<TimeSpan>, IEquatable<TimeSpan>, IFormattable, ISpanFormattable
     {
         public const long TicksPerMillisecond = 10000;
         private const double MillisecondsPerTick = 1.0 / TicksPerMillisecond;
diff --git a/src/mscorlib/shared/System/UInt16.cs b/src/mscorlib/shared/System/UInt16.cs
@@ -13,7 +13,7 @@ namespace System
     [CLSCompliant(false)]
     [StructLayout(LayoutKind.Sequential)]
     [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
-    public struct UInt16 : IComparable, IConvertible, IFormattable, IComparable<UInt16>, IEquatable<UInt16>
+    public struct UInt16 : IComparable, IConvertible, IFormattable, IComparable<UInt16>, IEquatable<UInt16>, ISpanFormattable
     {
         private ushort m_value; // Do not rename (binary serialization)
 
diff --git a/src/mscorlib/shared/System/UInt32.cs b/src/mscorlib/shared/System/UInt32.cs
@@ -13,7 +13,7 @@ namespace System
     [CLSCompliant(false)]
     [StructLayout(LayoutKind.Sequential)]
     [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
-    public struct UInt32 : IComparable, IConvertible, IFormattable, IComparable<UInt32>, IEquatable<UInt32>
+    public struct UInt32 : IComparable, IConvertible, IFormattable, IComparable<UInt32>, IEquatable<UInt32>, ISpanFormattable
     {
         private uint m_value; // Do not rename (binary serialization)
 
diff --git a/src/mscorlib/shared/System/UInt64.cs b/src/mscorlib/shared/System/UInt64.cs
@@ -13,7 +13,7 @@ namespace System
     [CLSCompliant(false)]
     [StructLayout(LayoutKind.Sequential)]
     [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
-    public struct UInt64 : IComparable, IConvertible, IFormattable, IComparable<UInt64>, IEquatable<UInt64>
+    public struct UInt64 : IComparable, IConvertible, IFormattable, IComparable<UInt64>, IEquatable<UInt64>, ISpanFormattable
     {
         private ulong m_value; // Do not rename (binary serialization)
 
diff --git a/src/mscorlib/shared/System/Version.cs b/src/mscorlib/shared/System/Version.cs
@@ -16,8 +16,7 @@ namespace System
 
     [Serializable]
     [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
-    public sealed class Version : ICloneable, IComparable
-        , IComparable<Version>, IEquatable<Version>
+    public sealed class Version : ICloneable, IComparable, IComparable<Version>, IEquatable<Version>, ISpanFormattable
     {
         // AssemblyName depends on the order staying the same
         private readonly int _Major; // Do not rename (binary serialization)
@@ -228,6 +227,12 @@ public bool TryFormat(Span<char> destination, int fieldCount, out int charsWritt
             return false;
         }
 
+        bool ISpanFormattable.TryFormat(Span<char> destination, out int charsWritten, string format, IFormatProvider provider)
+        {
+            // format and provider are ignored.
+            return TryFormat(destination, out charsWritten);
+        }
+
         private int DefaultFormatFieldCount =>
             _Build == -1 ? 2 :
             _Revision == -1 ? 3 :

Original file line number	Diff line number	Diff line change
`@@ -12,7 +12,7 @@ namespace System`
`12`	`12`	`[Serializable]`
`13`	`13`	`[StructLayout(LayoutKind.Sequential)]`
`14`	`14`	`[TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]`
`15`		`- public struct Byte : IComparable, IConvertible, IFormattable, IComparable<Byte>, IEquatable<Byte>`
	`15`	`+ public struct Byte : IComparable, IConvertible, IFormattable, IComparable<Byte>, IEquatable<Byte>, ISpanFormattable`
`16`	`16`	`{`
`17`	`17`	`private byte m_value; // Do not rename (binary serialization)`
`18`	`18`
Original file line number	Diff line number	Diff line change
`@@ -53,7 +53,7 @@ namespace System`
`53`	`53`	`[StructLayout(LayoutKind.Auto)]`
`54`	`54`	`[Serializable]`
`55`	`55`	`[System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]`
`56`		`- public readonly partial struct DateTime : IComparable, IFormattable, IConvertible, IComparable<DateTime>, IEquatable<DateTime>, ISerializable`
	`56`	`+ public readonly partial struct DateTime : IComparable, IFormattable, IConvertible, IComparable<DateTime>, IEquatable<DateTime>, ISerializable, ISpanFormattable`
`57`	`57`	`{`
`58`	`58`	`// Number of 100ns ticks per time unit`
`59`	`59`	`private const long TicksPerMillisecond = 10000;`
Original file line number	Diff line number	Diff line change
`@@ -31,7 +31,7 @@ namespace System`
`31`	`31`	`[StructLayout(LayoutKind.Auto)]`
`32`	`32`	`[Serializable]`
`33`	`33`	`[System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]`
`34`		`- public struct DateTimeOffset : IComparable, IFormattable, IComparable<DateTimeOffset>, IEquatable<DateTimeOffset>, ISerializable, IDeserializationCallback`
	`34`	`+ public struct DateTimeOffset : IComparable, IFormattable, IComparable<DateTimeOffset>, IEquatable<DateTimeOffset>, ISerializable, IDeserializationCallback, ISpanFormattable`
`35`	`35`	`{`
`36`	`36`	`// Constants`
`37`	`37`	`internal const Int64 MaxOffset = TimeSpan.TicksPerHour * 14;`
Original file line number	Diff line number	Diff line change
`@@ -13,7 +13,7 @@ namespace System`
`13`	`13`	`[Serializable]`
`14`	`14`	`[Runtime.Versioning.NonVersionable] // This only applies to field layout`
`15`	`15`	`[TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]`
`16`		`- public partial struct Guid : IFormattable, IComparable, IComparable<Guid>, IEquatable<Guid>`
	`16`	`+ public partial struct Guid : IFormattable, IComparable, IComparable<Guid>, IEquatable<Guid>, ISpanFormattable`
`17`	`17`	`{`
`18`	`18`	`public static readonly Guid Empty = new Guid();`
`19`	`19`
`@@ -1426,5 +1426,11 @@ public bool TryFormat(Span<char> destination, out int charsWritten, string forma`
`1426`	`1426`	`charsWritten = guidSize;`
`1427`	`1427`	`return true;`
`1428`	`1428`	`}`
	`1429`	`+`
	`1430`	`+ bool ISpanFormattable.TryFormat(Span<char> destination, out int charsWritten, string format, IFormatProvider provider)`
	`1431`	`+ {`
	`1432`	`+ // Like with the IFormattable implementation, provider is ignored.`
	`1433`	`+ return TryFormat(destination, out charsWritten, format);`
	`1434`	`+ }`
`1429`	`1435`	`}`
`1430`	`1436`	`}`