readChunked(fileHandle:fromOffset:byteCount:chunkSize:allocator:eventLoop:chunkHandler:)
Read byteCount bytes from offset fileOffset in chunks of chunkSize bytes from fileHandle in NonBlockingFileIO’s private thread pool which is separate from any EventLoop thread.
@preconcurrency func readChunked(fileHandle: NIOFileHandle, fromOffset fileOffset: Int64, byteCount: Int, chunkSize: Int = NonBlockingFileIO.defaultChunkSize, allocator: ByteBufferAllocator, eventLoop: any EventLoop, chunkHandler: @escaping (ByteBuffer) -> EventLoopFuture<Void>) -> EventLoopFuture<Void> Parameters
- fileHandle
The
NIOFileHandleto read from.- fileOffset
The offset into the file at which the read should begin.
- byteCount
The number of bytes to read from
fileHandle.- chunkSize
The size of the individual chunks to deliver.
- allocator
A
ByteBufferAllocatorused to allocate space for the chunks.- eventLoop
The
EventLoopto callchunkHandleron.- chunkHandler
Called for every chunk read. The next chunk will be read upon successful completion of the returned
EventLoopFuture. If the returnedEventLoopFuturefails, the overall operation is aborted.
Returns
An EventLoopFuture which is the result of the overall operation. If either the reading of fileHandle or chunkHandler fails, the EventLoopFuture will fail too. If the reading of fileHandle as well as chunkHandler always succeeded, the EventLoopFuture will succeed too.
chunkHandler will be called on eventLoop for every chunk that was read. Assuming byteCount is greater than zero and there are enough bytes available chunkHandler will be called 1 + |_ byteCount / chunkSize _| times, delivering chunkSize bytes each time. If less than byteCount bytes can be read from descriptor, chunkHandler will be called less often with the last invocation possibly being of less than chunkSize bytes.
The allocation and reading of a subsequent chunk will only be attempted when chunkHandler succeeds.
This method will not use the file descriptor’s seek pointer which means there is no danger of reading from the same NIOFileHandle in multiple threads.