Round #893

Use Memory<byte> and ArrayPool<byte>.Shared to read a file in 4KB chunks without re-allocating buffers per iteration. No async.

**Reading a File in 4KB Chunks using Memory<byte> and ArrayPool<byte>.Shared** Below is an example of how to read a file in 4KB chunks without re-allocating buffers per iteration using `Memory<byte>` and `ArrayPool<byte>.Shared` in C#. ```csharp using System; using System.IO; using System.Buffers; public class FileChunkReader { private const int ChunkSize = 4096; // 4KB public static void ReadFileInChunks(string filePath) { using var fileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read); var buffer = ArrayPool<byte>.Shared.Rent(ChunkSize); try { var bytesRead = 0; while ((bytesRead = fileStream.Read(buffer, 0, ChunkSize)) > 0) { var chunk = new Memory<byte>(buffer, 0, bytesRead); ProcessChunk(chunk); } } finally { ArrayPool<byte>.Shared.Return(buffer); } } private static void ProcessChunk(Memory<byte> chunk) { // Process the chunk as needed Console.WriteLine($"Read {chunk.Length} bytes"); } public static void Main(string[] args) { ReadFileInChunks("path_to_your_file.txt"); } } ``` **Explanation** 1. We define a constant `ChunkSize` for the size of each chunk (4KB in this case). 2. We create a `FileStream` to read the file and rent a buffer from `ArrayPool<byte>.Shared` with the specified `ChunkSize`. 3. We read the file in chunks using a `while` loop, where we read up to `ChunkSize` bytes into the rented buffer. 4. We create a `Memory<byte>` instance to represent the chunk, using the rented buffer and the number of bytes actually read. 5. We process the chunk as needed (in this example, we simply print the number of bytes read). 6. Finally, we return the rented buffer to the pool when we're done with it, regardless of whether an exception is thrown or not. **Benefits** * Using `ArrayPool<byte>.Shared` reduces memory allocation and garbage collection overhead, as the same buffer is reused across iterations. * Using `Memory<byte>` provides a safe and efficient way to work with the rented buffer, without having to worry about buffer overflows or invalid memory access.

```csharp using System; using System.Buffers; using System.IO; public class FileChunkReader { public static void ReadFileInChunks(string filePath) { using var fileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read); var buffer = ArrayPool<byte>.Shared.Rent(4096); try { var bytesRead = 0; while ((bytesRead = fileStream.Read(buffer, 0, 4096)) > 0) { var chunk = buffer.AsMemory(0, bytesRead); // Process the chunk ProcessChunk(chunk); } } finally { ArrayPool<byte>.Shared.Return(buffer); } } private static void ProcessChunk(Memory<byte> chunk) { // Replace with actual processing logic Console.WriteLine($"Read {chunk.Length} bytes"); } } ``` This implementation uses `ArrayPool<byte>.Shared` to rent a buffer of 4KB, which is then used to read the file in chunks. The `Read` method of the `FileStream` is used to read the file, and the `AsMemory` method is used to create a `Memory<byte>` instance from the rented buffer, which represents the actual chunk of data read from the file. The `ProcessChunk` method is a placeholder for the actual processing logic. After the file has been fully read, the rented buffer is returned to the pool using `ArrayPool<byte>.Shared.Return`.