[Libguestfs] [PATCH v5] v2v: Add --print-estimate option to print copy size estimate.

[Pino Toscano]

On Thursday, 23 August 2018 20:13:21 CEST Richard W.M. Jones wrote:
> 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
> 1 1047920640
> total 1047920640

Maybe having a slightly more user friendly output in non-machine
readable mode would be nice...

> +  let json = Filename.temp_file "v2vmeasure" ".json" in
> +  unlink_on_exit json;
> +
> +  let fd = Unix.openfile json [O_WRONLY; O_CREAT; O_TRUNC] 0o600 in

  let chan, json = Filename.open_temp_file "v2vmeasure" ".json" in
  unlink_on_exit json;
  let fd = Unix.descr_of_out_channel chan in
  
> +  let json = read_whole_file json in
> +  debug "qemu-img measure output: %s" json;
> +  let json = json_parser_tree_parse json in

I just pushed json_parser_tree_parse_file, so that can be used instead
using read_whole_file.

> +echo -n "Estimate: "
> +cat $f
> +
> +# Check the output looks reasonable.
> +grep -E 'total.*[[:digit:]]+' $f

Maybe using a tool like jd to check the keys in the JSON dict would
be cleaner.

-- 
Pino Toscano
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