Re: [Libguestfs] [PATCH v3 4/4] v2v: Add --print-estimate option to print copy size estimate.

This option prints the estimated size of the data that will be copied from the source disk. Currently this overestimates by the size of the qcow2 header, but for real disk images that doesn't matter much. For example: $ virt-builder fedora-27 $ virt-v2v -i disk fedora-27.img -o null --print-estimate [...] virt-v2v: This guest has virtio drivers installed. [ 44.0] Mapping filesystem data to avoid copying unused and blank areas [ 44.5] Closing the overlay 1047920640

+ let fd = Unix.openfile json [O_WRONLY; O_CREAT; O_TRUNC] 0o600 in + if run_command ~stdout_fd:fd !cmd <> 0 then + error (f_"qemu-img measure failed, see earlier errors"); + (* Note that run_command closes fd. *) + + let json = read_whole_file json in

+ (* We're expecting the tree to contain nodes: + * object [| "required", number; "fully-allocated", number |] + * Of course the array could appear in any order. + *) + match tree with + | JSON_parser_object fields -> + let fields = Array.to_list fields in + let rq = + try List.assoc "required" fields + with Not_found -> + error_unexpected_output (s_"expecting \"required\" field") json in + (match rq with + | JSON_parser_number i64 -> + i64 + | _ -> + error_unexpected_output (s_"expecting \"required\" to be an integer") + json + ) + | _ -> + error_unexpected_output (s_"expecting object at top level") json