of_string s creates a source from a complete string. Useful for testing streaming code paths with known input.

of_channel ?buf_size ic creates a source that reads from ic. buf_size controls the internal read buffer (default 4096).

of_function read creates a source that calls read buf off len to obtain up to len bytes starting at offset off in buf. Must return the number of bytes actually read; return 0 to signal EOF.

This is the low-level escape hatch for byte sources that fill a pre-allocated buffer, such as Unix.read or Unix.recv. For most use cases, prefer of_chunks or of_seq.

of_chunks read creates a source that calls read () to obtain the next chunk of input. Return Some s with a non-empty string for data, or None to signal EOF. Empty strings (Some "") are silently skipped.

This is the recommended way to wrap effectful or callback-based data sources:

(* Eio promise *)
let fetched = ref false in
let source = Source.of_chunks (fun () ->
    if !fetched then None
    else begin
      fetched := true;
      Some (Promise.await_exn promise)
    end)

of_seq seq creates a source from a lazy sequence of string chunks. Each element is a chunk of input; the sequence ending (Seq.Nil) signals EOF.

let source = Source.of_seq (List.to_seq [ "chunk1"; "chunk2"; "chunk3" ])