update based on review comments

src/Microsoft.OData.Core/Json/ODataUtf8JsonWriter.cs

@@ -18,8 +18,6 @@
 using Microsoft.OData.Edm;
 using System.Text.Unicode;
 using System.Buffers.Text;
-using System.Net.NetworkInformation;
-using System.Data.Common;
 
 namespace Microsoft.OData.Json
 {
@@ -86,6 +84,11 @@ internal sealed class ODataUtf8JsonWriter : IJsonWriter, IDisposable, IJsonWrite
         /// </summary>
         private bool isWritingAtStartOfArray = false;
         /// <summary>
+        /// Whether we're about to write the first element in array. This helps
+        /// decide whether we should manually write a separator.
+        /// </summary>
+        private bool isWritinglargeByteArrayAtStartOfArray = false;
+        /// <summary>
         /// Whether we're currently writing a raw value at the start of an array
         /// or preceeded by a sequence of consecutive raw values at the start of
         /// an array e.g. ["rawValue1", "rawValue2", "rawValue3"
@@ -401,9 +404,15 @@ public void WriteValue(string value)
         /// </remarks>
         private void WriteStringValueInChunks(ReadOnlySpan<char> value)
         {
-            this.CommitUtf8JsonWriterContentsToBuffer(); 
-            this.bufferWriter.Write(doubleQuote.Slice(0, 1).Span);
+            this.CommitUtf8JsonWriterContentsToBuffer();
             this.Flush();
+            if (IsInArray() && !isWritingAtStartOfArray)
+            {
+                // Place a separator before the raw value if
+                // this is an array, unless this is the first item in the array.
+                this.bufferWriter.Write(itemSeparator.Slice(0, 1).Span);
+            }
+            this.bufferWriter.Write(doubleQuote.Slice(0, 1).Span);
 
             int chunkSize = 2048;
 
@@ -442,6 +451,82 @@ private void WriteStringValueInChunks(ReadOnlySpan<char> value)
             // since we bypass the Utf8JsonWriter, we need to signal to other
             // Write methods that a separator should be written first
             CheckIfSeparatorNeeded();
+
+            if (this.isWritingAtStartOfArray || this.isWritingConsecutiveRawValuesAtStartOfArray)
+            {
+                this.isWritingConsecutiveRawValuesAtStartOfArray = true;
+            }
+
+            this.isWritingAtStartOfArray = false;
+        }
+
+        /// <summary>
+        /// Writes a string value into the buffer in chunks asynchronously, handling escaping if necessary.
+        /// </summary>
+        /// <param name="value">The string value to write.</param>
+        /// <remarks>
+        /// This method writes the provided string value into the buffer in manageable chunks to avoid
+        /// excessive memory allocations and buffer overflows. If the string requires escaping, it is
+        /// processed accordingly to ensure correct JSON formatting.
+        /// </remarks>
+        private async ValueTask WriteStringValueInChunksAsync(ReadOnlyMemory<char> value)
+        {
+            this.CommitUtf8JsonWriterContentsToBuffer();
+            await this.FlushAsync();
+
+            if (IsInArray() && !isWritingAtStartOfArray)
+            {
+                // Place a separator before the raw value if
+                // this is an array, unless this is the first item in the array.
+                this.bufferWriter.Write(itemSeparator.Slice(0, 1).Span);
+            }
+
+            this.bufferWriter.Write(doubleQuote.Slice(0, 1).Span);
+
+            int chunkSize = 2048;
+
+            for (int i = 0; i < value.Length; i += chunkSize)
+            {
+                int remainingChars = Math.Min(chunkSize, value.Length - i);
+                bool isFinalBlock = (i + remainingChars) == value.Length;
+                int bytesWritten = 0;
+
+                ReadOnlyMemory<char> chunk = value.Slice(i, remainingChars);
+
+                int firstIndexToEscape = NeedsEscaping(chunk.Span);
+
+                Debug.Assert(firstIndexToEscape >= -1 && firstIndexToEscape < value.Length);
+
+                if (firstIndexToEscape != -1)
+                {
+                    if (bytesWritten > 0 && bytesWritten < chunk.Length)
+                    {
+                        chunk = value.Slice(i - bytesWritten, bytesWritten + chunkSize);
+                    }
+
+                    WriteEscapedStringChunk(chunk.Span, firstIndexToEscape, isFinalBlock, out bytesWritten);
+                }
+                else
+                {
+                    WriteStringChunk(chunk.Span, isFinalBlock);
+                }
+
+                // Flush the buffer if needed
+                await this.FlushIfBufferThresholdReachedAsync();
+            }
+
+            this.bufferWriter.Write(doubleQuote.Slice(0, 1).Span);
+
+            // since we bypass the Utf8JsonWriter, we need to signal to other
+            // Write methods that a separator should be written first
+            CheckIfSeparatorNeeded();
+
+            if (this.isWritingAtStartOfArray || this.isWritingConsecutiveRawValuesAtStartOfArray)
+            {
+                this.isWritingConsecutiveRawValuesAtStartOfArray = true;
+            }
+
+            this.isWritingAtStartOfArray = false;
         }
 
         /// <summary>
@@ -587,7 +672,7 @@ public void WriteValue(byte[] value)
             {
                 this.utf8JsonWriter.WriteBase64StringValue(value);
             }
-            
+
             this.FlushIfBufferThresholdReached();
         }
 
@@ -598,9 +683,17 @@ public void WriteValue(byte[] value)
         private void WriteByteValueInChunks(ReadOnlySpan<byte> value)
         {
             this.CommitUtf8JsonWriterContentsToBuffer();
-            this.bufferWriter.Write(doubleQuote.Slice(0, 1).Span);
             this.Flush();
 
+            if (IsInArray() && !isWritingAtStartOfArray)
+            {
+                // Place a separator before the raw value if
+                // this is an array, unless this is the first item in the array.
+                this.bufferWriter.Write(itemSeparator.Slice(0, 1).Span);
+            }
+
+            this.bufferWriter.Write(doubleQuote.Slice(0, 1).Span);
+
             int chunkSize = 2732;
 
             int prevBytesNotWritten = 0;
@@ -622,6 +715,61 @@ private void WriteByteValueInChunks(ReadOnlySpan<byte> value)
             // since we bypass the Utf8JsonWriter, we need to signal to other
             // Write methods that a separator should be written first
             CheckIfSeparatorNeeded();
+
+            if (this.isWritingAtStartOfArray || this.isWritingConsecutiveRawValuesAtStartOfArray)
+            {
+                this.isWritingConsecutiveRawValuesAtStartOfArray = true;
+            }
+
+            this.isWritingAtStartOfArray = false;
+        }
+
+        /// <summary>
+        /// Writes the byte value represented by the provided ReadOnlySpan in chunks using Base64 encoding.
+        /// </summary>
+        /// <param name="value">The ReadOnlySpan containing the byte value to be written.</param>
+        private async ValueTask WriteByteValueInChunksAsync(ReadOnlyMemory<byte> value)
+        {
+            this.CommitUtf8JsonWriterContentsToBuffer();
+            await FlushAsync().ConfigureAwait(false);
+
+            if (IsInArray() && !isWritingAtStartOfArray)
+            {
+                // Place a separator before the raw value if
+                // this is an array, unless this is the first item in the array.
+                this.bufferWriter.Write(itemSeparator.Slice(0, 1).Span);
+            }
+
+            this.bufferWriter.Write(doubleQuote.Slice(0, 1).Span);
+
+            int chunkSize = 2732;
+
+            int prevBytesNotWritten = 0;
+
+            for (int i = 0; i < value.Length; i += chunkSize)
+            {
+                int remainingChars = Math.Min(chunkSize, value.Length - i);
+                bool isFinalBlock = (i + remainingChars) == value.Length;
+
+                ReadOnlyMemory<byte> chunk = value.Slice(i - prevBytesNotWritten, remainingChars + prevBytesNotWritten);
+
+                Base64EncodeAndWriteChunk(chunk.Span, isFinalBlock, out prevBytesNotWritten);
+
+                await FlushIfBufferThresholdReachedAsync().ConfigureAwait(false);
+            }
+
+            this.bufferWriter.Write(doubleQuote.Slice(0, 1).Span);
+
+            // since we bypass the Utf8JsonWriter, we need to signal to other
+            // Write methods that a separator should be written first
+            CheckIfSeparatorNeeded();
+
+            if (this.isWritingAtStartOfArray || this.isWritingConsecutiveRawValuesAtStartOfArray)
+            {
+                this.isWritingConsecutiveRawValuesAtStartOfArray = true;
+            }
+
+            this.isWritingAtStartOfArray = false;
         }
 
         /// <summary>
@@ -746,6 +894,7 @@ private void EnterArrayScope()
         {
             this.isWritingConsecutiveRawValuesAtStartOfArray = false;
             this.isWritingAtStartOfArray = true;
+            this.isWritinglargeByteArrayAtStartOfArray = true;
             this.bitStack.PushFalse();
         }
 
@@ -1045,17 +1194,18 @@ public async Task WriteValueAsync(sbyte value)
 
         public async Task WriteValueAsync(string value)
         {
-            this.WriteSeparatorIfNecessary();
             if (value == null)
             {
+                this.WriteSeparatorIfNecessary();
                 this.utf8JsonWriter.WriteNullValue();
             }
             else if (value.Length > bufferWriter.FreeCapacity)
             {
-                WriteStringValueInChunks(value.AsSpan());
+                await WriteStringValueInChunksAsync(value.AsMemory());
             }
             else
             {
+                this.WriteSeparatorIfNecessary();
                 this.utf8JsonWriter.WriteStringValue(value.ToString());
             }
 
@@ -1064,17 +1214,18 @@ public async Task WriteValueAsync(string value)
 
         public async Task WriteValueAsync(byte[] value)
         {
-            this.WriteSeparatorIfNecessary();
             if (value == null)
             {
+                this.WriteSeparatorIfNecessary();
                 this.utf8JsonWriter.WriteNullValue();
             }
             else if (value.Length > bufferWriter.Capacity)
             {
-                WriteByteValueInChunks(value.AsSpan());
+                await WriteByteValueInChunksAsync(value);
             }
             else
             {
+                this.WriteSeparatorIfNecessary();
                 this.utf8JsonWriter.WriteBase64StringValue(value);
             }