[FEATURE]: utilise block map (.bmap) files for faster write/verify.

[burtyb]

Is your feature request related to a problem? Please describe.

Block map (.bmap) files have been distributed alongside the Raspberry Pi OS images for around 4 months but as far as I can see they're not currently used by rpi-imager.

Describe the solution you would like to see implemented

Add support to use an optional block map file via a "url_bmap" option (or something) per OS in the JSON configuration file to help speed up writing (and verifying) media.

Describe alternatives you've considered

Whilst bmaptool can be used to write OS images using the block map data it would then require manual configuration.

Additional context

The only downside I can see is you get no "verify" on the skipped blocks to identify issues with the media but since it's most likely going to expand the partition into unwritten blocks on first boot it's minor.

Version

2.0.2 (Default)

[tdewey-rpi]

We've been separately looking at bmap & android-sparse formats, and I'm much more inclined to support android-sparse because it doesn't require a sidecar file.

For reference, rpi-sb-provisioner uses android-sparse files today, and the improvement in write times is dramatic.