Add APIs to BlobBuilder for customizing the underlying byte array et al.

src/libraries/System.Reflection.Metadata/ref/System.Reflection.Metadata.cs

@@ -227,8 +227,11 @@ public readonly partial struct Blob
     }
     public partial class BlobBuilder
     {
+        protected BlobBuilder(byte[] buffer, int maxChunkSize = 0) { }
         public BlobBuilder(int capacity = 256) { }
         protected internal int ChunkCapacity { get { throw null; } }
+        protected internal byte[] Buffer { get { throw null; } set { } }
+        public int Capacity { get { throw null; } set { } }
         public int Count { get { throw null; } }
         protected int FreeBytes { get { throw null; } }
         public void Align(int alignment) { }
@@ -240,6 +243,7 @@ protected virtual void FreeChunk() { }
         public System.Reflection.Metadata.BlobBuilder.Blobs GetBlobs() { throw null; }
         public void LinkPrefix(System.Reflection.Metadata.BlobBuilder prefix) { }
         public void LinkSuffix(System.Reflection.Metadata.BlobBuilder suffix) { }
+        protected virtual void OnLinking(System.Reflection.Metadata.BlobBuilder other) { }
         public void PadTo(int position) { }
         public System.Reflection.Metadata.Blob ReserveBytes(int byteCount) { throw null; }
         public byte[] ToArray() { throw null; }
@@ -255,6 +259,7 @@ public void WriteBytes(byte[] buffer) { }
         public void WriteBytes(byte[] buffer, int start, int byteCount) { }
         public void WriteBytes(System.Collections.Immutable.ImmutableArray<byte> buffer) { }
         public void WriteBytes(System.Collections.Immutable.ImmutableArray<byte> buffer, int start, int byteCount) { }
+        public void WriteBytes(System.ReadOnlySpan<byte> buffer) { }
         public void WriteCompressedInteger(int value) { }
         public void WriteCompressedSignedInteger(int value) { }
         public void WriteConstant(object? value) { }
@@ -2805,7 +2810,9 @@ public MetadataAggregator(System.Reflection.Metadata.MetadataReader baseReader,
     }
     public sealed partial class MetadataBuilder
     {
+        [System.ComponentModel.EditorBrowsableAttribute(System.ComponentModel.EditorBrowsableState.Never)]
         public MetadataBuilder(int userStringHeapStartOffset = 0, int stringHeapStartOffset = 0, int blobHeapStartOffset = 0, int guidHeapStartOffset = 0) { }
+        public MetadataBuilder(int userStringHeapStartOffset = 0, int stringHeapStartOffset = 0, int blobHeapStartOffset = 0, int guidHeapStartOffset = 0, System.Func<int, System.Reflection.Metadata.BlobBuilder>? createBlobBuilderFunc = null) { }
         public System.Reflection.Metadata.AssemblyDefinitionHandle AddAssembly(System.Reflection.Metadata.StringHandle name, System.Version version, System.Reflection.Metadata.StringHandle culture, System.Reflection.Metadata.BlobHandle publicKey, System.Reflection.AssemblyFlags flags, System.Reflection.AssemblyHashAlgorithm hashAlgorithm) { throw null; }
         public System.Reflection.Metadata.AssemblyFileHandle AddAssemblyFile(System.Reflection.Metadata.StringHandle name, System.Reflection.Metadata.BlobHandle hashValue, bool containsMetadata) { throw null; }
         public System.Reflection.Metadata.AssemblyReferenceHandle AddAssemblyReference(System.Reflection.Metadata.StringHandle name, System.Version version, System.Reflection.Metadata.StringHandle culture, System.Reflection.Metadata.BlobHandle publicKeyOrToken, System.Reflection.AssemblyFlags flags, System.Reflection.Metadata.BlobHandle hashValue) { throw null; }
@@ -3265,6 +3272,7 @@ internal CorHeader() { }
     public sealed partial class DebugDirectoryBuilder
     {
         public DebugDirectoryBuilder() { }
+        public DebugDirectoryBuilder(System.Reflection.Metadata.BlobBuilder blobBuilder) { }
         public void AddCodeViewEntry(string pdbPath, System.Reflection.Metadata.BlobContentId pdbContentId, ushort portablePdbVersion) { }
         public void AddCodeViewEntry(string pdbPath, System.Reflection.Metadata.BlobContentId pdbContentId, ushort portablePdbVersion, int age) { }
         public void AddEmbeddedPortablePdbEntry(System.Reflection.Metadata.BlobBuilder debugMetadata, ushort portablePdbVersion) { }
@@ -3358,6 +3366,7 @@ public partial class ManagedPEBuilder : System.Reflection.PortableExecutable.PEB
         public const int ManagedResourcesDataAlignment = 8;
         public const int MappedFieldDataAlignment = 8;
         public ManagedPEBuilder(System.Reflection.PortableExecutable.PEHeaderBuilder header, System.Reflection.Metadata.Ecma335.MetadataRootBuilder metadataRootBuilder, System.Reflection.Metadata.BlobBuilder ilStream, System.Reflection.Metadata.BlobBuilder? mappedFieldData = null, System.Reflection.Metadata.BlobBuilder? managedResources = null, System.Reflection.PortableExecutable.ResourceSectionBuilder? nativeResources = null, System.Reflection.PortableExecutable.DebugDirectoryBuilder? debugDirectoryBuilder = null, int strongNameSignatureSize = 128, System.Reflection.Metadata.MethodDefinitionHandle entryPoint = default(System.Reflection.Metadata.MethodDefinitionHandle), System.Reflection.PortableExecutable.CorFlags flags = System.Reflection.PortableExecutable.CorFlags.ILOnly, System.Func<System.Collections.Generic.IEnumerable<System.Reflection.Metadata.Blob>, System.Reflection.Metadata.BlobContentId>? deterministicIdProvider = null) : base (default(System.Reflection.PortableExecutable.PEHeaderBuilder), default(System.Func<System.Collections.Generic.IEnumerable<System.Reflection.Metadata.Blob>, System.Reflection.Metadata.BlobContentId>)) { }
+        protected virtual System.Reflection.Metadata.BlobBuilder CreateBlobBuilder(int minimumSize = 0) { throw null; }
         protected override System.Collections.Immutable.ImmutableArray<System.Reflection.PortableExecutable.PEBuilder.Section> CreateSections() { throw null; }
         protected internal override System.Reflection.PortableExecutable.PEDirectoriesBuilder GetDirectories() { throw null; }
         protected override System.Reflection.Metadata.BlobBuilder SerializeSection(string name, System.Reflection.PortableExecutable.SectionLocation location) { throw null; }

src/libraries/System.Reflection.Metadata/src/System/Reflection/Internal/Utilities/BlobUtilities.cs

@@ -5,6 +5,13 @@
 using System.Diagnostics;
 using System.Reflection.Internal;
 using System.Runtime.CompilerServices;
+#if NET
+using System.Buffers;
+using System.Text.Unicode;
+#else
+using System.Runtime.InteropServices;
+using System.Text;
+#endif
 
 namespace System.Reflection
 {
@@ -61,125 +68,135 @@ public static void WriteGuid(this byte[] buffer, int start, Guid value)
             Debug.Assert(written);
         }
 
-        public static unsafe void WriteUTF8(this byte[] buffer, int start, char* charPtr, int charCount, int byteCount, bool allowUnpairedSurrogates)
+#if NET
+        public static void WriteUtf8(ReadOnlySpan<char> source, Span<byte> destination, out int charsRead, out int bytesWritten, bool allowUnpairedSurrogates)
         {
-            Debug.Assert(byteCount >= charCount);
-            const char ReplacementCharacter = '\uFFFD';
+            int sourceLength = source.Length;
+            int destinationLength = destination.Length;
 
-            char* strEnd = charPtr + charCount;
-            fixed (byte* bufferPtr = &buffer[0])
+            while (true)
             {
-                byte* ptr = bufferPtr + start;
+                OperationStatus status = Utf8.FromUtf16(source, destination, out int consumed, out int written, replaceInvalidSequences: !allowUnpairedSurrogates, isFinalBlock: true);
+                source = source.Slice(consumed);
+                destination = destination.Slice(written);
 
-                if (byteCount == charCount)
+                if (status <= OperationStatus.DestinationTooSmall)
                 {
-                    while (charPtr < strEnd)
-                    {
-                        Debug.Assert(*charPtr <= 0x7f);
-                        *ptr++ = unchecked((byte)*charPtr++);
-                    }
+                    break;
                 }
-                else
+
+                // NeedsMoreData is not expected because isFinalBlock is set to true.
+                Debug.Assert(status == OperationStatus.InvalidData);
+                // If we don't allow unpaired surrogates, they should have been replaced by FromUtf16.
+                Debug.Assert(allowUnpairedSurrogates);
+                char c = source[0];
+                Debug.Assert(char.IsSurrogate(c));
+                if (destination.Length < 3)
                 {
-                    while (charPtr < strEnd)
-                    {
-                        char c = *charPtr++;
+                    break;
+                }
+                destination[0] = (byte)(((c >> 12) & 0xF) | 0xE0);
+                destination[1] = (byte)(((c >> 6) & 0x3F) | 0x80);
+                destination[2] = (byte)((c & 0x3F) | 0x80);
+                source = source.Slice(1);
+                destination = destination.Slice(3);
+            }
 
+            charsRead = sourceLength - source.Length;
+            bytesWritten = destinationLength - destination.Length;
+        }
+#else
+        public static void WriteUtf8(ReadOnlySpan<char> source, Span<byte> destination, out int charsRead, out int bytesWritten, bool allowUnpairedSurrogates)
+        {
+            const char ReplacementCharacter = '\uFFFD';
+
+            int sourceLength = source.Length;
+            int destinationLength = destination.Length;
+
+            unsafe
+            {
+                fixed (char* pSource = &MemoryMarshal.GetReference(source))
+                fixed (byte* pDestination = &MemoryMarshal.GetReference(destination))
+                {
+                    char* src = pSource, srcEnd = pSource + source.Length;
+                    byte* dst = pDestination, dstEnd = pDestination + destination.Length;
+
+                    while (src < srcEnd)
+                    {
+                        char c = *src;
                         if (c < 0x80)
                         {
-                            *ptr++ = (byte)c;
-                            continue;
+                            if (dstEnd - dst < 1)
+                            {
+                                break;
+                            }
+                            *dst++ = (byte)c;
+                            src++;
                         }
-
-                        if (c < 0x800)
+                        else if (c < 0x800)
                         {
-                            ptr[0] = (byte)(((c >> 6) & 0x1F) | 0xC0);
-                            ptr[1] = (byte)((c & 0x3F) | 0x80);
-                            ptr += 2;
-                            continue;
+                            if (dstEnd - dst < 2)
+                            {
+                                break;
+                            }
+                            *dst++ = (byte)((c >> 6) | 0xC0);
+                            *dst++ = (byte)((c & 0x3F) | 0x80);
+                            src++;
                         }
-
-                        if (char.IsSurrogate(c))
+                        else
                         {
-                            // surrogate pair
-                            if (char.IsHighSurrogate(c) && charPtr < strEnd && char.IsLowSurrogate(*charPtr))
+                            if (char.IsSurrogate(c))
                             {
-                                int highSurrogate = c;
-                                int lowSurrogate = *charPtr++;
-                                int codepoint = (((highSurrogate - 0xd800) << 10) + lowSurrogate - 0xdc00) + 0x10000;
-                                ptr[0] = (byte)(((codepoint >> 18) & 0x7) | 0xF0);
-                                ptr[1] = (byte)(((codepoint >> 12) & 0x3F) | 0x80);
-                                ptr[2] = (byte)(((codepoint >> 6) & 0x3F) | 0x80);
-                                ptr[3] = (byte)((codepoint & 0x3F) | 0x80);
-                                ptr += 4;
-                                continue;
+                                // surrogate pair
+                                if (char.IsHighSurrogate(c) && srcEnd - src >= 2 && src[1] is char cLow && char.IsLowSurrogate(cLow))
+                                {
+                                    if (dstEnd - dst < 4)
+                                    {
+                                        break;
+                                    }
+                                    int codepoint = ((c - 0xd800) << 10) + cLow - 0xdc00 + 0x10000;
+                                    *dst++ = (byte)((codepoint >> 18) | 0xF0);
+                                    *dst++ = (byte)(((codepoint >> 12) & 0x3F) | 0x80);
+                                    *dst++ = (byte)(((codepoint >> 6) & 0x3F) | 0x80);
+                                    *dst++ = (byte)((codepoint & 0x3F) | 0x80);
+                                    src += 2;
+                                    continue;
+                                }
+
+                                // unpaired high/low surrogate
+                                if (!allowUnpairedSurrogates)
+                                {
+                                    c = ReplacementCharacter;
+                                }
                             }
 
-                            // unpaired high/low surrogate
-                            if (!allowUnpairedSurrogates)
+                            if (dstEnd - dst < 3)
                             {
-                                c = ReplacementCharacter;
+                                break;
                             }
+                            *dst++ = (byte)((c >> 12) | 0xE0);
+                            *dst++ = (byte)(((c >> 6) & 0x3F) | 0x80);
+                            *dst++ = (byte)((c & 0x3F) | 0x80);
+                            src++;
                         }
-
-                        ptr[0] = (byte)(((c >> 12) & 0xF) | 0xE0);
-                        ptr[1] = (byte)(((c >> 6) & 0x3F) | 0x80);
-                        ptr[2] = (byte)((c & 0x3F) | 0x80);
-                        ptr += 3;
                     }
-                }
 
-                Debug.Assert(ptr == bufferPtr + start + byteCount);
-                Debug.Assert(charPtr == strEnd);
+                    charsRead = (int)(src - pSource);
+                    bytesWritten = (int)(dst - pDestination);
+                }
             }
         }
+#endif
 
-        internal static unsafe int GetUTF8ByteCount(char* str, int charCount)
+#if !NET
+        internal static unsafe int GetByteCount(this Encoding encoding, ReadOnlySpan<char> str)
         {
-            return GetUTF8ByteCount(str, charCount, int.MaxValue, out _);
-        }
-
-        internal static unsafe int GetUTF8ByteCount(char* str, int charCount, int byteLimit, out char* remainder)
-        {
-            char* end = str + charCount;
-
-            char* ptr = str;
-            int byteCount = 0;
-            while (ptr < end)
+            fixed (char* ptr = &MemoryMarshal.GetReference(str))
             {
-                int characterSize;
-                char c = *ptr++;
-                if (c < 0x80)
-                {
-                    characterSize = 1;
-                }
-                else if (c < 0x800)
-                {
-                    characterSize = 2;
-                }
-                else if (char.IsHighSurrogate(c) && ptr < end && char.IsLowSurrogate(*ptr))
-                {
-                    // surrogate pair:
-                    characterSize = 4;
-                    ptr++;
-                }
-                else
-                {
-                    characterSize = 3;
-                }
-
-                if (byteCount + characterSize > byteLimit)
-                {
-                    ptr -= (characterSize < 4) ? 1 : 2;
-                    break;
-                }
-
-                byteCount += characterSize;
+                return encoding.GetByteCount(ptr, str.Length);
             }
-
-            remainder = ptr;
-            return byteCount;
         }
+#endif
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         internal static void ValidateRange(int bufferLength, int start, int byteCount, string byteCountParameterName)