Add public Encoding.TryGetBytes/Chars (#85120)

src/libraries/System.Formats.Asn1/src/System/Formats/Asn1/AsnDecoder.Text.cs

@@ -390,16 +390,19 @@ private static unsafe bool TryReadCharacterStringCore(
             Text.Encoding encoding,
             out int charsWritten)
         {
-            if (source.Length == 0)
+            try
             {
-                charsWritten = 0;
-                return true;
-            }
+#if NET8_0_OR_GREATER
+                return encoding.TryGetChars(source, destination, out charsWritten);
+#else
+                if (source.Length == 0)
+                {
+                    charsWritten = 0;
+                    return true;
+                }
 
-            fixed (byte* bytePtr = &MemoryMarshal.GetReference(source))
-            fixed (char* charPtr = &MemoryMarshal.GetReference(destination))
-            {
-                try
+                fixed (byte* bytePtr = &MemoryMarshal.GetReference(source))
+                fixed (char* charPtr = &MemoryMarshal.GetReference(destination))
                 {
                     int charCount = encoding.GetCharCount(bytePtr, source.Length);
 
@@ -411,13 +414,14 @@ private static unsafe bool TryReadCharacterStringCore(
 
                     charsWritten = encoding.GetChars(bytePtr, source.Length, charPtr, destination.Length);
                     Debug.Assert(charCount == charsWritten);
-                }
-                catch (DecoderFallbackException e)
-                {
-                    throw new AsnContentException(SR.ContentException_DefaultMessage, e);
-                }
 
-                return true;
+                    return true;
+                }
+#endif
+            }
+            catch (DecoderFallbackException e)
+            {
+                throw new AsnContentException(SR.ContentException_DefaultMessage, e);
             }
         }
 

src/libraries/System.Formats.Asn1/tests/Reader/ReadUTF8String.cs

@@ -148,16 +148,13 @@ public static void TryCopyUTF8String(
 
             if (output.Length > 0)
             {
-                output[0] = 'a';
-
                 copied = reader.TryReadCharacterString(
                     output.AsSpan(0, expectedValue.Length - 1),
                     UniversalTagNumber.UTF8String,
                     out charsWritten);
 
                 Assert.False(copied, "reader.TryCopyUTF8String - too short");
                 Assert.Equal(0, charsWritten);
-                Assert.Equal('a', output[0]);
             }
 
             copied = reader.TryReadCharacterString(

src/libraries/System.Private.CoreLib/src/System/Text/ASCIIEncoding.cs

@@ -322,13 +322,8 @@ public override unsafe int GetBytes(ReadOnlySpan<char> chars, Span<byte> bytes)
             }
         }
 
-        // TODO https://github.com/dotnet/runtime/issues/84425: Make this public.
-        /// <summary>Encodes into a span of bytes a set of characters from the specified read-only span if the destination is large enough.</summary>
-        /// <param name="chars">The span containing the set of characters to encode.</param>
-        /// <param name="bytes">The byte span to hold the encoded bytes.</param>
-        /// <param name="bytesWritten">Upon successful completion of the operation, the number of bytes encoded into <paramref name="bytes"/>.</param>
-        /// <returns><see langword="true"/> if all of the characters were encoded into the destination; <see langword="false"/> if the destination was too small to contain all the encoded bytes.</returns>
-        internal override unsafe bool TryGetBytes(ReadOnlySpan<char> chars, Span<byte> bytes, out int bytesWritten)
+        /// <inheritdoc/>
+        public override unsafe bool TryGetBytes(ReadOnlySpan<char> chars, Span<byte> bytes, out int bytesWritten)
         {
             fixed (char* charsPtr = &MemoryMarshal.GetReference(chars))
             fixed (byte* bytesPtr = &MemoryMarshal.GetReference(bytes))
@@ -618,8 +613,26 @@ public override unsafe int GetChars(ReadOnlySpan<byte> bytes, Span<char> chars)
             }
         }
 
+        /// <inheritdoc/>
+        public override unsafe bool TryGetChars(ReadOnlySpan<byte> bytes, Span<char> chars, out int charsWritten)
+        {
+            fixed (byte* bytesPtr = &MemoryMarshal.GetReference(bytes))
+            fixed (char* charsPtr = &MemoryMarshal.GetReference(chars))
+            {
+                int written = GetCharsCommon(bytesPtr, bytes.Length, charsPtr, chars.Length, throwForDestinationOverflow: false);
+                if (written >= 0)
+                {
+                    charsWritten = written;
+                    return true;
+                }
+
+                charsWritten = 0;
+                return false;
+            }
+        }
+
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private unsafe int GetCharsCommon(byte* pBytes, int byteCount, char* pChars, int charCount)
+        private unsafe int GetCharsCommon(byte* pBytes, int byteCount, char* pChars, int charCount, bool throwForDestinationOverflow = true)
         {
             // Common helper method for all non-DecoderNLS entry points to GetChars.
             // A modification of this method should be copied in to each of the supported encodings: ASCII, UTF8, UTF16, UTF32.
@@ -643,7 +656,7 @@ private unsafe int GetCharsCommon(byte* pBytes, int byteCount, char* pChars, int
             {
                 // Simple narrowing conversion couldn't operate on entire buffer - invoke fallback.
 
-                return GetCharsWithFallback(pBytes, byteCount, pChars, charCount, bytesConsumed, charsWritten);
+                return GetCharsWithFallback(pBytes, byteCount, pChars, charCount, bytesConsumed, charsWritten, throwForDestinationOverflow);
             }
         }
 
@@ -654,7 +667,7 @@ private protected sealed override unsafe int GetCharsFast(byte* pBytes, int byte
             return bytesConsumed;
         }
 
-        private protected sealed override unsafe int GetCharsWithFallback(ReadOnlySpan<byte> bytes, int originalBytesLength, Span<char> chars, int originalCharsLength, DecoderNLS? decoder)
+        private protected sealed override unsafe int GetCharsWithFallback(ReadOnlySpan<byte> bytes, int originalBytesLength, Span<char> chars, int originalCharsLength, DecoderNLS? decoder, bool throwForDestinationOverflow = true)
         {
             // We special-case DecoderReplacementFallback if it's telling us to write a single BMP char,
             // since we believe this to be relatively common and we can handle it more efficiently than
@@ -699,7 +712,7 @@ private protected sealed override unsafe int GetCharsWithFallback(ReadOnlySpan<b
             }
             else
             {
-                return base.GetCharsWithFallback(bytes, originalBytesLength, chars, originalCharsLength, decoder);
+                return base.GetCharsWithFallback(bytes, originalBytesLength, chars, originalCharsLength, decoder, throwForDestinationOverflow);
             }
         }
 

src/libraries/System.Private.CoreLib/src/System/Text/Encoding.Internal.cs

@@ -1081,7 +1081,7 @@ private protected virtual unsafe int GetCharsFast(byte* pBytes, int bytesLength,
         /// If the destination buffer is not large enough to hold the entirety of the transcoded data.
         /// </exception>
         [MethodImpl(MethodImplOptions.NoInlining)]
-        private protected unsafe int GetCharsWithFallback(byte* pOriginalBytes, int originalByteCount, char* pOriginalChars, int originalCharCount, int bytesConsumedSoFar, int charsWrittenSoFar)
+        private protected unsafe int GetCharsWithFallback(byte* pOriginalBytes, int originalByteCount, char* pOriginalChars, int originalCharCount, int bytesConsumedSoFar, int charsWrittenSoFar, bool throwForDestinationOverflow = true)
         {
             // This is a stub method that's marked "no-inlining" so that it we don't stack-spill spans
             // into our immediate caller. Doing so increases the method prolog in what's supposed to
@@ -1095,7 +1095,8 @@ private protected unsafe int GetCharsWithFallback(byte* pOriginalBytes, int orig
                 originalBytesLength: originalByteCount,
                 chars: new Span<char>(pOriginalChars, originalCharCount).Slice(charsWrittenSoFar),
                 originalCharsLength: originalCharCount,
-                decoder: null);
+                decoder: null,
+                throwForDestinationOverflow);
         }
 
         /// <summary>
@@ -1104,7 +1105,7 @@ private protected unsafe int GetCharsWithFallback(byte* pOriginalBytes, int orig
         /// and <paramref name="charsWrittenSoFar"/> signal where in the provided buffers the fallback loop
         /// should begin operating. The behavior of this method is to drain any leftover data in the
         /// <see cref="DecoderNLS"/> instance, then to invoke the <see cref="GetCharsFast"/> virtual method
-        /// after data has been drained, then to call <see cref="GetCharsWithFallback(ReadOnlySpan{byte}, int, Span{char}, int, DecoderNLS)"/>.
+        /// after data has been drained, then to call GetCharsWithFallback(ReadOnlySpan{byte}, int, Span{char}, int, DecoderNLS, out bool)/>.
         /// </summary>
         /// <returns>
         /// The total number of chars written to <paramref name="pOriginalChars"/>, including <paramref name="charsWrittenSoFar"/>.
@@ -1183,7 +1184,7 @@ private protected unsafe int GetCharsWithFallback(byte* pOriginalBytes, int orig
         /// implementation, deferring to the base implementation if needed. This method calls <see cref="ThrowCharsOverflow"/>
         /// if necessary.
         /// </remarks>
-        private protected virtual unsafe int GetCharsWithFallback(ReadOnlySpan<byte> bytes, int originalBytesLength, Span<char> chars, int originalCharsLength, DecoderNLS? decoder)
+        private protected virtual unsafe int GetCharsWithFallback(ReadOnlySpan<byte> bytes, int originalBytesLength, Span<char> chars, int originalCharsLength, DecoderNLS? decoder, bool throwForDestinationOverflow = true)
         {
             Debug.Assert(!bytes.IsEmpty, "Caller shouldn't invoke this method with an empty input buffer.");
             Debug.Assert(originalBytesLength >= 0, "Caller provided invalid parameter.");
@@ -1272,11 +1273,18 @@ private protected virtual unsafe int GetCharsWithFallback(ReadOnlySpan<byte> byt
 
                 if (!bytes.IsEmpty)
                 {
-                    // The line below will also throw if the decoder couldn't make any progress at all
-                    // because the output buffer wasn't large enough to contain the result of even
-                    // a single scalar conversion or fallback.
-
-                    ThrowCharsOverflow(decoder, nothingDecoded: chars.Length == originalCharsLength);
+                    if (throwForDestinationOverflow)
+                    {
+                        // The line below will also throw if the decoder couldn't make any progress at all
+                        // because the output buffer wasn't large enough to contain the result of even
+                        // a single scalar conversion or fallback.
+                        ThrowCharsOverflow(decoder, nothingDecoded: chars.Length == originalCharsLength);
+                    }
+                    else
+                    {
+                        Debug.Assert(decoder is null);
+                        return -1;
+                    }
                 }
 
                 // If a DecoderNLS instance is active, update its "total consumed byte count" value.

src/libraries/System.Private.CoreLib/src/System/Text/Encoding.cs

@@ -733,13 +733,12 @@ public virtual unsafe int GetBytes(ReadOnlySpan<char> chars, Span<byte> bytes)
             }
         }
 
-        // TODO https://github.com/dotnet/runtime/issues/84425: Make this public.
         /// <summary>Encodes into a span of bytes a set of characters from the specified read-only span if the destination is large enough.</summary>
         /// <param name="chars">The span containing the set of characters to encode.</param>
         /// <param name="bytes">The byte span to hold the encoded bytes.</param>
         /// <param name="bytesWritten">Upon successful completion of the operation, the number of bytes encoded into <paramref name="bytes"/>.</param>
         /// <returns><see langword="true"/> if all of the characters were encoded into the destination; <see langword="false"/> if the destination was too small to contain all the encoded bytes.</returns>
-        internal virtual bool TryGetBytes(ReadOnlySpan<char> chars, Span<byte> bytes, out int bytesWritten)
+        public virtual bool TryGetBytes(ReadOnlySpan<char> chars, Span<byte> bytes, out int bytesWritten)
         {
             int required = GetByteCount(chars);
             if (required <= bytes.Length)
@@ -883,6 +882,24 @@ public virtual unsafe int GetChars(ReadOnlySpan<byte> bytes, Span<char> chars)
             }
         }
 
+        /// <summary>Decodes into a span of chars a set of bytes from the specified read-only span if the destination is large enough.</summary>
+        /// <param name="bytes">A read-only span containing the sequence of bytes to decode.</param>
+        /// <param name="chars">The character span receiving the decoded bytes.</param>
+        /// <param name="charsWritten">Upon successful completion of the operation, the number of chars decoded into <paramref name="chars"/>.</param>
+        /// <returns><see langword="true"/> if all of the characters were decoded into the destination; <see langword="false"/> if the destination was too small to contain all the decoded chars.</returns>
+        public virtual bool TryGetChars(ReadOnlySpan<byte> bytes, Span<char> chars, out int charsWritten)
+        {
+            int required = GetCharCount(bytes);
+            if (required <= chars.Length)
+            {
+                charsWritten = GetChars(bytes, chars);
+                return true;
+            }
+
+            charsWritten = 0;
+            return false;
+        }
+
         [CLSCompliant(false)]
         public unsafe string GetString(byte* bytes, int byteCount)
         {

src/libraries/System.Private.CoreLib/src/System/Text/Latin1Encoding.cs

@@ -234,13 +234,8 @@ public override unsafe int GetBytes(ReadOnlySpan<char> chars, Span<byte> bytes)
             }
         }
 
-        // TODO https://github.com/dotnet/runtime/issues/84425: Make this public.
-        /// <summary>Encodes into a span of bytes a set of characters from the specified read-only span if the destination is large enough.</summary>
-        /// <param name="chars">The span containing the set of characters to encode.</param>
-        /// <param name="bytes">The byte span to hold the encoded bytes.</param>
-        /// <param name="bytesWritten">Upon successful completion of the operation, the number of bytes encoded into <paramref name="bytes"/>.</param>
-        /// <returns><see langword="true"/> if all of the characters were encoded into the destination; <see langword="false"/> if the destination was too small to contain all the encoded bytes.</returns>
-        internal override unsafe bool TryGetBytes(ReadOnlySpan<char> chars, Span<byte> bytes, out int bytesWritten)
+        /// <inheritdoc/>
+        public override unsafe bool TryGetBytes(ReadOnlySpan<char> chars, Span<byte> bytes, out int bytesWritten)
         {
             fixed (char* charsPtr = &MemoryMarshal.GetReference(chars))
             fixed (byte* bytesPtr = &MemoryMarshal.GetReference(bytes))
@@ -534,6 +529,23 @@ public override unsafe int GetChars(ReadOnlySpan<byte> bytes, Span<char> chars)
             }
         }
 
+        /// <inheritdoc/>
+        public override unsafe bool TryGetChars(ReadOnlySpan<byte> bytes, Span<char> chars, out int charsWritten)
+        {
+            if (bytes.Length <= chars.Length)
+            {
+                fixed (byte* bytesPtr = &MemoryMarshal.GetReference(bytes))
+                fixed (char* charsPtr = &MemoryMarshal.GetReference(chars))
+                {
+                    charsWritten = GetCharsCommon(bytesPtr, bytes.Length, charsPtr, chars.Length);
+                    return true;
+                }
+            }
+
+            charsWritten = 0;
+            return false;
+        }
+
         public override unsafe string GetString(byte[] bytes)
         {
             if (bytes is null)

src/libraries/System.Private.CoreLib/src/System/Text/UTF8Encoding.Sealed.cs

@@ -147,9 +147,9 @@ private unsafe string GetStringForSmallInput(byte[] bytes)
                 return new string(new ReadOnlySpan<char>(ref *pDestination, charsWritten)); // this overload of ROS ctor doesn't validate length
             }
 
-            // TODO https://github.com/dotnet/runtime/issues/84425: Make this public.
             // TODO: Make this [Intrinsic] and handle JIT-time UTF8 encoding of literal `chars`.
-            internal override unsafe bool TryGetBytes(ReadOnlySpan<char> chars, Span<byte> bytes, out int bytesWritten)
+            /// <inheritdoc/>
+            public override unsafe bool TryGetBytes(ReadOnlySpan<char> chars, Span<byte> bytes, out int bytesWritten)
             {
                 return base.TryGetBytes(chars, bytes, out bytesWritten);
             }