tree 8999d3ad88f5ad403d3e6fc4b8bcec3a0f6729a3
parent a5c51c9cee2ce0ce324ac05c4a461a611fe274e2
author Akilesh Kailash <akailash@google.com> 1693813639 -0700
committer Akilesh Kailash <akailash@google.com> 1693953731 -0700

create_snapshot: Create snapshot patch comparing two partition images

This is a host based tool wherein it compares two Android images and generates snapshot patches which are similar to Android OTA format.

There are few advantages:

1: All the computation of snapshot logic is pushed onto the host.
2: Each partition can have different compression algorithm.
3: All the libsnapshot_cow changes can be tested very quickly.

Here is the test run. This compares two builds which are 24 hours apart.

```

create_snapshot --source=$ANDROID_PRODUCT_OUT/system.img --target=./images/system.img --compression="zstd" &
create_snapshot --source=$ANDROID_PRODUCT_OUT/product.img --target=./images/product.img --compression="lz4" &
create_snapshot --source=$ANDROID_PRODUCT_OUT/vendor.img --target=./images/vendor.img &
create_snapshot --source=$ANDROID_PRODUCT_OUT/system_ext.img --target=./images/system_ext.img --compression="gz" &
create_snapshot --source=$ANDROID_PRODUCT_OUT/vendor_dlkm.img --target=./images/vendor_dlkm.img &

echo "Waiting for snapshot patch creation"
wait $(jobs -p)
echo "Snapshot patch creation completed"
```

========================================
Waiting for snapshot patch creation
Snapshot patch: vendor_dlkm.patch created successfully
Snapshot patch: vendor.patch created successfully
Snapshot patch: system_ext.patch created successfully
Snapshot patch: product.patch created successfully
Snapshot patch: system.patch created successfully
Snapshot patch creation completed

real	0m3.848s
user	0m14.239s
sys	0m8.045s
========================================

It takes ~4 seconds to generate the snapshot patches on the host. Snapshot patches are named as <partition-name>.patch.

Bug: 299011882
Test: create_snapshot between two builds as mentioned above.
Change-Id: Ic87dd3349a866b5626fa03f1f879f417a8116cc2
Signed-off-by: Akilesh Kailash <akailash@google.com>