Re: [Libguestfs] [libnbd PATCH v4 19/25] ocaml: Add example for 64-bit extents

Since our example program for 32-bit extents is inherently limited to 32-bit lengths, it is also worth demonstrating the 64-bit extent API, including the difference in the array indexing being saner. Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; Reviewed-by: Richard W.M. Jones <rjones(a)redhat.com&gt; --- v4: no change --- ocaml/examples/Makefile.am | 1 + ocaml/examples/extents64.ml | 42 +++++++++++++++++++++++++++++++++++++ 2 files changed, 43 insertions(+) create mode 100644 ocaml/examples/extents64.ml diff --git a/ocaml/examples/Makefile.am b/ocaml/examples/Makefile.am index 28b4ab94..a4eb47a5 100644 --- a/ocaml/examples/Makefile.am +++ b/ocaml/examples/Makefile.am @@ -20,6 +20,7 @@ include $(top_srcdir)/subdir-rules.mk ml_examples = \ asynch_copy.ml \ extents.ml \ + extents64.ml \ get_size.ml \ open_qcow2.ml \ server_flags.ml \ diff --git a/ocaml/examples/extents64.ml b/ocaml/examples/extents64.ml new file mode 100644 index 00000000..8ee7e218 --- /dev/null +++ b/ocaml/examples/extents64.ml @@ -0,0 +1,42 @@ +open Printf + +let () = + NBD.with_handle ( + fun nbd -> + NBD.add_meta_context nbd "base:allocation"; + NBD.connect_command nbd + ["nbdkit"; "-s"; "--exit-with-parent"; "-r"; + "sparse-random"; "8G"]; + + (* Read the extents and print them. *) + let size = NBD.get_size nbd in + let cap = + match NBD.get_extended_headers_negotiated nbd with + | true -> size + | false -> 0x8000_0000_L in + let fetch_offset = ref 0_L in + while !fetch_offset < size do + let remaining = Int64.sub size !fetch_offset in + let fetch_size = min remaining cap in + NBD.block_status_64 nbd fetch_size !fetch_offset ( + fun meta _ entries err -> + printf "nbd_block_status callback: meta=%s err=%d\n" meta !err; + if meta = "base:allocation" then ( + printf "index\t%16s %16s %s\n" "offset" "length" "flags"; + for i = 0 to Array.length entries - 1 do + let len = fst entries.(i) + and flags = + match snd entries.(i) with + | 0_L -> "data" + | 1_L -> "hole" + | 2_L -> "zero" + | 3_L -> "hole+zero" + | unknown -> sprintf "unknown (%Ld)" unknown in + printf "%d:\t%16Ld %16Ld %s\n" i !fetch_offset len flags; + fetch_offset := Int64.add !fetch_offset len + done; + ); + 0 + ) (* NBD.block_status *) + done + )