Use memory allocator for all text chunks

Author: ynse01

src/ImageSharp/Formats/Png/PngEncoderCore.cs

@@ -739,21 +739,33 @@ private void WriteTextChunks(Stream stream, PngMetadata meta)
                     byte[] translatedKeyword = PngConstants.TranslatedEncoding.GetBytes(textData.TranslatedKeyword);
                     byte[] languageTag = PngConstants.LanguageEncoding.GetBytes(textData.LanguageTag);
 
-                    Span<byte> outputBytes = new byte[keywordBytes.Length + textBytes.Length +
-                                                      translatedKeyword.Length + languageTag.Length + 5];
-                    keywordBytes.CopyTo(outputBytes);
-                    if (textData.Value.Length > this.options.TextCompressionThreshold)
+                    int payloadLength = keywordBytes.Length + textBytes.Length + translatedKeyword.Length + languageTag.Length + 5;
+                    using (IMemoryOwner<byte> owner = this.memoryAllocator.Allocate<byte>(payloadLength))
                     {
-                        // Indicate that the text is compressed.
-                        outputBytes[keywordBytes.Length + 1] = 1;
-                    }
+                        Span<byte> outputBytes = owner.GetSpan();
+                        keywordBytes.CopyTo(outputBytes);
+                        int bytesWritten = keywordBytes.Length;
+                        outputBytes[bytesWritten++] = 0;
+                        if (textData.Value.Length > this.options.TextCompressionThreshold)
+                        {
+                            // Indicate that the text is compressed.
+                            outputBytes[bytesWritten++] = 1;
+                        }
+                        else
+                        {
+                            outputBytes[bytesWritten++] = 0;
+                        }
 
-                    int keywordStart = keywordBytes.Length + 3;
-                    languageTag.CopyTo(outputBytes.Slice(keywordStart));
-                    int translatedKeywordStart = keywordStart + languageTag.Length + 1;
-                    translatedKeyword.CopyTo(outputBytes.Slice(translatedKeywordStart));
-                    textBytes.CopyTo(outputBytes.Slice(translatedKeywordStart + translatedKeyword.Length + 1));
-                    this.WriteChunk(stream, PngChunkType.InternationalText, outputBytes.ToArray());
+                        outputBytes[bytesWritten++] = 0;
+                        languageTag.CopyTo(outputBytes.Slice(bytesWritten));
+                        bytesWritten += languageTag.Length;
+                        outputBytes[bytesWritten++] = 0;
+                        translatedKeyword.CopyTo(outputBytes.Slice(bytesWritten));
+                        bytesWritten += translatedKeyword.Length;
+                        outputBytes[bytesWritten++] = 0;
+                        textBytes.CopyTo(outputBytes.Slice(bytesWritten));
+                        this.WriteChunk(stream, PngChunkType.InternationalText, outputBytes);
+                    }
                 }
                 else
                 {
@@ -762,19 +774,32 @@ private void WriteTextChunks(Stream stream, PngMetadata meta)
                         // Write zTXt chunk.
                         byte[] compressedData =
                             this.GetCompressedTextBytes(PngConstants.Encoding.GetBytes(textData.Value));
-                        Span<byte> outputBytes = new byte[textData.Keyword.Length + compressedData.Length + 2];
-                        PngConstants.Encoding.GetBytes(textData.Keyword).CopyTo(outputBytes);
-                        compressedData.CopyTo(outputBytes.Slice(textData.Keyword.Length + 2));
-                        this.WriteChunk(stream, PngChunkType.CompressedText, outputBytes.ToArray());
+                        int payloadLength = textData.Keyword.Length + compressedData.Length + 2;
+                        using (IMemoryOwner<byte> owner = this.memoryAllocator.Allocate<byte>(payloadLength))
+                        {
+                            Span<byte> outputBytes = owner.GetSpan();
+                            PngConstants.Encoding.GetBytes(textData.Keyword).CopyTo(outputBytes);
+                            int bytesWritten = textData.Keyword.Length;
+                            outputBytes[bytesWritten++] = 0;
+                            outputBytes[bytesWritten++] = 0;
+                            compressedData.CopyTo(outputBytes.Slice(bytesWritten));
+                            this.WriteChunk(stream, PngChunkType.CompressedText, outputBytes.ToArray());
+                        }
                     }
                     else
                     {
                         // Write tEXt chunk.
-                        Span<byte> outputBytes = new byte[textData.Keyword.Length + textData.Value.Length + 1];
-                        PngConstants.Encoding.GetBytes(textData.Keyword).CopyTo(outputBytes);
-                        PngConstants.Encoding.GetBytes(textData.Value)
-                            .CopyTo(outputBytes.Slice(textData.Keyword.Length + 1));
-                        this.WriteChunk(stream, PngChunkType.Text, outputBytes.ToArray());
+                        int payloadLength = textData.Keyword.Length + textData.Value.Length + 1;
+                        using (IMemoryOwner<byte> owner = this.memoryAllocator.Allocate<byte>(payloadLength))
+                        {
+                            Span<byte> outputBytes = owner.GetSpan();
+                            PngConstants.Encoding.GetBytes(textData.Keyword).CopyTo(outputBytes);
+                            int bytesWritten = textData.Keyword.Length;
+                            outputBytes[bytesWritten++] = 0;
+                            PngConstants.Encoding.GetBytes(textData.Value)
+                                .CopyTo(outputBytes.Slice(bytesWritten));
+                            this.WriteChunk(stream, PngChunkType.Text, outputBytes.ToArray());
+                        }
                     }
                 }
             }