Split the writing and reading part of section data

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/ObjectWriter/CodeView/CodeViewFileTableBuilder.cs

@@ -54,21 +54,14 @@ public uint GetFileIndex(string fileName)
             }
         }
 
-        public void Write(Stream sectionStream)
+        public void Write(SectionWriter sectionWriter)
         {
-            Span<byte> subsectionHeader = stackalloc byte[sizeof(uint) + sizeof(uint)];
-
-            BinaryPrimitives.WriteUInt32LittleEndian(subsectionHeader, (uint)DebugSymbolsSubsectionType.FileChecksums);
-            BinaryPrimitives.WriteUInt32LittleEndian(subsectionHeader.Slice(4), (uint)_fileTableWriter.Length);
-            sectionStream.Write(subsectionHeader);
-            _fileTableWriter.Position = 0;
-            _fileTableWriter.CopyTo(sectionStream);
-
-            BinaryPrimitives.WriteUInt32LittleEndian(subsectionHeader, (uint)DebugSymbolsSubsectionType.StringTable);
-            BinaryPrimitives.WriteUInt32LittleEndian(subsectionHeader.Slice(4), (uint)_stringTableWriter.Length);
-            sectionStream.Write(subsectionHeader);
-            _stringTableWriter.Position = 0;
-            _stringTableWriter.CopyTo(sectionStream);
+            sectionWriter.WriteLittleEndian<uint>((uint)DebugSymbolsSubsectionType.FileChecksums);
+            sectionWriter.WriteLittleEndian<uint>((uint)_fileTableWriter.Length);
+            sectionWriter.EmitData(_fileTableWriter.GetBuffer().AsMemory(0, (int)_fileTableWriter.Length));
+            sectionWriter.WriteLittleEndian<uint>((uint)DebugSymbolsSubsectionType.StringTable);
+            sectionWriter.WriteLittleEndian<uint>((uint)_stringTableWriter.Length);
+            sectionWriter.EmitData(_stringTableWriter.GetBuffer().AsMemory(0, (int)_stringTableWriter.Length));
         }
     }
 }

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/ObjectWriter/CodeView/CodeViewSymbolsBuilder.cs

@@ -51,7 +51,7 @@ public CodeViewSymbolsBuilder(TargetArchitecture targetArchitecture, SectionWrit
             // Write CodeView version header
             Span<byte> versionBuffer = stackalloc byte[sizeof(uint)];
             BinaryPrimitives.WriteUInt32LittleEndian(versionBuffer, 4);
-            sectionWriter.Stream.Write(versionBuffer);
+            sectionWriter.Write(versionBuffer);
         }
 
         // Maps an ICorDebugInfo register number to the corresponding CodeView
@@ -310,7 +310,7 @@ public void Dispose()
                 Span<byte> subsectionHeader = stackalloc byte[sizeof(uint) + sizeof(uint)];
                 BinaryPrimitives.WriteUInt32LittleEndian(subsectionHeader, (uint)_kind);
                 BinaryPrimitives.WriteUInt32LittleEndian(subsectionHeader.Slice(4), _size);
-                _sectionWriter.Stream.Write(subsectionHeader);
+                _sectionWriter.Write(subsectionHeader);
 
                 foreach (var (offset, relocType, symbolName) in _relocations)
                 {
@@ -324,7 +324,7 @@ public void Dispose()
 
                 foreach (byte[] data in _data)
                 {
-                    _sectionWriter.Stream.Write(data);
+                    _sectionWriter.Write(data);
                 }
 
                 _sectionWriter.EmitAlignment(4);

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/ObjectWriter/CodeView/CodeViewTypesBuilder.cs

@@ -39,7 +39,7 @@ namespace ILCompiler.ObjectWriter
     internal sealed class CodeViewTypesBuilder : ITypesDebugInfoWriter
     {
         private NameMangler _nameMangler;
-        private Stream _outputStream;
+        private SectionWriter _sectionWriter;
         private int _targetPointerSize;
 
         private uint _classVTableTypeIndex;
@@ -50,10 +50,10 @@ internal sealed class CodeViewTypesBuilder : ITypesDebugInfoWriter
 
         public IList<(string, uint)> UserDefinedTypes => _userDefinedTypes;
 
-        public CodeViewTypesBuilder(NameMangler nameMangler, TargetArchitecture targetArchitecture, Stream outputStream)
+        public CodeViewTypesBuilder(NameMangler nameMangler, TargetArchitecture targetArchitecture, SectionWriter sectionWriter)
         {
             _nameMangler = nameMangler;
-            _outputStream = outputStream;
+            _sectionWriter = sectionWriter;
             _targetPointerSize = targetArchitecture switch
             {
                 TargetArchitecture.ARM => 4,
@@ -64,7 +64,7 @@ public CodeViewTypesBuilder(NameMangler nameMangler, TargetArchitecture targetAr
             // Write CodeView version header
             Span<byte> versionBuffer = stackalloc byte[sizeof(uint)];
             BinaryPrimitives.WriteUInt32LittleEndian(versionBuffer, 4);
-            _outputStream.Write(versionBuffer);
+            _sectionWriter.Write(versionBuffer);
 
             // We pretend that the MethodTable pointer in System.Object is VTable shape.
             // We use the same "Vtable" for all types because the vtable shape debug
@@ -418,9 +418,9 @@ public void Dispose()
                 Debug.Assert(length <= ushort.MaxValue);
                 Span<byte> lengthBuffer = stackalloc byte[sizeof(ushort)];
                 BinaryPrimitives.WriteUInt16LittleEndian(lengthBuffer, (ushort)(length + padding - sizeof(ushort)));
-                _debugTypesBuilder._outputStream.Write(lengthBuffer);
-                _debugTypesBuilder._outputStream.Write(_bufferWriter.WrittenSpan);
-                _debugTypesBuilder._outputStream.Write(stackalloc byte[padding]);
+                _debugTypesBuilder._sectionWriter.Write(lengthBuffer);
+                _debugTypesBuilder._sectionWriter.Write(_bufferWriter.WrittenSpan);
+                _debugTypesBuilder._sectionWriter.Write(stackalloc byte[padding]);
                 _bufferWriter.Clear();
             }
 
@@ -517,11 +517,9 @@ public void EndListEntry()
                     // Flush the current record up to _lastListMemberStart and write LF_INDEX to reference it.
                     int length = sizeof(ushort) + _lastListMemberStart;
                     int padding = ((length + 3) & ~3) - length;
-                    Span<byte> lengthBuffer = stackalloc byte[sizeof(ushort)];
-                    BinaryPrimitives.WriteUInt16LittleEndian(lengthBuffer, (ushort)(length + padding - sizeof(ushort)));
-                    _debugTypesBuilder._outputStream.Write(lengthBuffer);
-                    _debugTypesBuilder._outputStream.Write(_bufferWriter.WrittenSpan.Slice(0, _lastListMemberStart));
-                    _debugTypesBuilder._outputStream.Write(stackalloc byte[padding]);
+                    _debugTypesBuilder._sectionWriter.WriteLittleEndian<ushort>((ushort)(length + padding - sizeof(ushort)));
+                    _debugTypesBuilder._sectionWriter.Write(_bufferWriter.WrittenSpan.Slice(0, _lastListMemberStart));
+                    _debugTypesBuilder._sectionWriter.Write(stackalloc byte[padding]);
                     byte[] overflow = _bufferWriter.WrittenSpan.Slice(_lastListMemberStart).ToArray();
                     _bufferWriter.Clear();
 

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/ObjectWriter/CoffObjectWriter.cs

@@ -274,11 +274,9 @@ protected override void EmitSymbolTable(
                 // Create section with control flow guard symbols
                 SectionWriter gfidsSectionWriter = GetOrCreateSection(GfidsSection);
 
-                Span<byte> tempBuffer = stackalloc byte[4];
                 foreach (var symbolName in _referencedMethods)
                 {
-                    BinaryPrimitives.WriteUInt32LittleEndian(tempBuffer, _symbolNameToIndex[symbolName]);
-                    gfidsSectionWriter.Stream.Write(tempBuffer);
+                    gfidsSectionWriter.WriteLittleEndian<uint>(_symbolNameToIndex[symbolName]);
                 }
 
                 // Emit the feat.00 symbol that controls various linker behaviors
@@ -436,13 +434,13 @@ protected override void EmitUnwindInfo(
                     xdataSectionWriter.EmitSymbolDefinition(unwindSymbolName);
 
                     // Emit UNWIND_INFO
-                    xdataSectionWriter.Stream.Write(blob);
+                    xdataSectionWriter.Write(blob);
 
                     FrameInfoFlags flags = frameInfo.Flags;
 
                     if (i != 0)
                     {
-                        xdataSectionWriter.Stream.WriteByte((byte)flags);
+                        xdataSectionWriter.WriteByte((byte)flags);
                     }
                     else
                     {
@@ -452,7 +450,7 @@ protected override void EmitUnwindInfo(
                         flags |= ehInfo != null ? FrameInfoFlags.HasEHInfo : 0;
                         flags |= associatedDataNode != null ? FrameInfoFlags.HasAssociatedData : 0;
 
-                        xdataSectionWriter.Stream.WriteByte((byte)flags);
+                        xdataSectionWriter.WriteByte((byte)flags);
 
                         if (associatedDataNode != null)
                         {
@@ -468,7 +466,7 @@ protected override void EmitUnwindInfo(
 
                         if (nodeWithCodeInfo.GCInfo != null)
                         {
-                            xdataSectionWriter.Stream.Write(nodeWithCodeInfo.GCInfo);
+                            xdataSectionWriter.Write(nodeWithCodeInfo.GCInfo);
                         }
                     }
 
@@ -614,7 +612,7 @@ protected override ITypesDebugInfoWriter CreateDebugInfoBuilder()
             _debugTypesSectionWriter.EmitAlignment(4);
             _debugTypesBuilder = new CodeViewTypesBuilder(
                 _nodeFactory.NameMangler, _nodeFactory.Target.Architecture,
-                _debugTypesSectionWriter.Stream);
+                _debugTypesSectionWriter);
             return _debugTypesBuilder;
         }
 
@@ -665,7 +663,7 @@ protected override void EmitDebugFunctionInfo(
         protected override void EmitDebugSections(IDictionary<string, SymbolDefinition> definedSymbols)
         {
             _debugSymbolsBuilder.WriteUserDefinedTypes(_debugTypesBuilder.UserDefinedTypes);
-            _debugFileTableBuilder.Write(_debugSymbolSectionWriter.Stream);
+            _debugFileTableBuilder.Write(_debugSymbolSectionWriter);
         }
 
         private sealed class CoffHeader

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/ObjectWriter/Dwarf/DwarfAbbrev.cs

@@ -22,32 +22,32 @@ public DwarfAbbrev(ushort[] definition)
 
         public int AbbreviationCode { get; set; }
 
-        public void Write(ObjectWriterStream stream, int targetPointerSize)
+        public void Write(SectionWriter writer, int targetPointerSize)
         {
-            stream.WriteULEB128((ulong)AbbreviationCode);
-            stream.WriteULEB128(Tag);
-            stream.WriteULEB128(HasChildren ? DW_CHILDREN_yes : DW_CHILDREN_no);
+            writer.WriteULEB128((ulong)AbbreviationCode);
+            writer.WriteULEB128(Tag);
+            writer.WriteULEB128(HasChildren ? DW_CHILDREN_yes : DW_CHILDREN_no);
 
             for (int i = 2; i < _definition.Length; i++)
             {
                 // Attribute
-                stream.WriteULEB128(_definition[i++]);
+                writer.WriteULEB128(_definition[i++]);
                 // Form
                 if (_definition[i] != DW_FORM_size)
                 {
-                    stream.WriteULEB128(_definition[i]);
+                    writer.WriteULEB128(_definition[i]);
                 }
                 else if (targetPointerSize == 8)
                 {
-                    stream.WriteULEB128(DW_FORM_data8);
+                    writer.WriteULEB128(DW_FORM_data8);
                 }
                 else if (targetPointerSize == 4)
                 {
-                    stream.WriteULEB128(DW_FORM_data4);
+                    writer.WriteULEB128(DW_FORM_data4);
                 }
             }
 
-            stream.Write([0, 0]);
+            writer.Write([0, 0]);
         }
 
         public static DwarfAbbrev CompileUnit = new([

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/ObjectWriter/Dwarf/DwarfBuilder.cs

@@ -122,13 +122,13 @@ public void WriteInfoTable(
         {
             // Length
             byte[] sizeBuffer = new byte[sizeof(uint)];
-            infoSectionWriter.Stream.AppendData(sizeBuffer);
+            infoSectionWriter.EmitData(sizeBuffer);
             // Version
-            infoSectionWriter.Stream.WriteLittleEndian<ushort>((ushort)(_useDwarf5 ? 5u : 4u));
+            infoSectionWriter.WriteLittleEndian<ushort>((ushort)(_useDwarf5 ? 5u : 4u));
             if (_useDwarf5)
             {
                 // Unit type, Address Size
-                infoSectionWriter.Stream.Write([DW_UT_compile, _targetPointerSize]);
+                infoSectionWriter.Write([DW_UT_compile, _targetPointerSize]);
                 // Abbrev offset
                 infoSectionWriter.EmitSymbolReference(RelocType.IMAGE_REL_BASED_HIGHLOW, ".debug_abbrev", 0);
             }
@@ -137,12 +137,12 @@ public void WriteInfoTable(
                 // Abbrev offset
                 infoSectionWriter.EmitSymbolReference(RelocType.IMAGE_REL_BASED_HIGHLOW, ".debug_abbrev", 0);
                 // Address Size
-                infoSectionWriter.Stream.Write([_targetPointerSize]);
+                infoSectionWriter.Write([_targetPointerSize]);
             }
 
             using (DwarfInfoWriter dwarfInfoWriter = new(
                 infoSectionWriter,
-                stringSectionWriter.Stream,
+                stringSectionWriter,
                 abbrevSectionWriter,
                 locSectionWriter,
                 rangeSectionWriter,
@@ -199,10 +199,10 @@ public void WriteInfoTable(
             }
 
             // End of compile unit
-            infoSectionWriter.Stream.Write([(byte)0]);
+            infoSectionWriter.WriteByte(0);
 
             // Update the size
-            BinaryPrimitives.WriteUInt32LittleEndian(sizeBuffer, (uint)(infoSectionWriter.Stream.Length - sizeof(uint)));
+            BinaryPrimitives.WriteUInt32LittleEndian(sizeBuffer, (uint)(infoSectionWriter.Position - sizeof(uint)));
         }
 
         private void WriteLineInfoTable(SectionWriter lineSectionWriter)
@@ -225,28 +225,28 @@ private void WriteAddressRangeTable(SectionWriter arangeSectionWriter)
         {
             // Length
             var sizeBuffer = new byte[sizeof(uint)];
-            arangeSectionWriter.Stream.AppendData(sizeBuffer);
+            arangeSectionWriter.EmitData(sizeBuffer);
             // Version
-            arangeSectionWriter.Stream.WriteLittleEndian<ushort>(2);
+            arangeSectionWriter.WriteLittleEndian<ushort>(2);
             // Debug Info Offset
             arangeSectionWriter.EmitSymbolReference(RelocType.IMAGE_REL_BASED_HIGHLOW, ".debug_info", 0);
             // Address size, Segment selector size
-            arangeSectionWriter.Stream.Write([_targetPointerSize, 0]);
+            arangeSectionWriter.Write([_targetPointerSize, 0]);
             // Ranges have to be aligned
             arangeSectionWriter.EmitAlignment(_targetPointerSize * 2);
             foreach (var sectionInfo in _sections)
             {
                 arangeSectionWriter.EmitSymbolReference(_codeRelocType, sectionInfo.SectionSymbolName, 0);
                 switch (_targetPointerSize)
                 {
-                    case 8: arangeSectionWriter.Stream.WriteLittleEndian<ulong>(sectionInfo.Size); break;
-                    case 4: arangeSectionWriter.Stream.WriteLittleEndian<uint>((uint)sectionInfo.Size); break;
+                    case 8: arangeSectionWriter.WriteLittleEndian<ulong>(sectionInfo.Size); break;
+                    case 4: arangeSectionWriter.WriteLittleEndian<uint>((uint)sectionInfo.Size); break;
                     default: throw new NotSupportedException();
                 }
             }
-            arangeSectionWriter.Stream.Write(stackalloc byte[_targetPointerSize * 2]);
+            arangeSectionWriter.Write(stackalloc byte[_targetPointerSize * 2]);
             // Update the size
-            BinaryPrimitives.WriteUInt32LittleEndian(sizeBuffer, (uint)(arangeSectionWriter.Stream.Length - sizeof(uint)));
+            BinaryPrimitives.WriteUInt32LittleEndian(sizeBuffer, (uint)(arangeSectionWriter.Position - sizeof(uint)));
         }
 
         public uint GetPrimitiveTypeIndex(TypeDesc type)