tree ab3c1c80ced95ae3979547a61206e9411a3333f8
parent f5a904e25dd9c05bc8cfab8cb74aba73c5652d83
author Sen Jiang <senj@google.com> 1540946371 -0700
committer Treehugger Robot <treehugger-gerrit@google.com> 1541192559 +0000

Consider diff operation overhead.

Storing a diff operation has more overhead over replace operation in
the manifest, we need to store an additional src_sha256_hash which is
32 bytes and not compressible, and also src_extents which could use
anywhere from a few bytes to hundreds of bytes depending on the
number of extents.

We should consider this overhead when deciding whether to use a diff
operation over a replace operation, replace operation should be
prefered if payload size is similar, because they don't rely on
existing data on disk and they could be merged with other replace
operations.

Test: brillo_update_payload generate
Test: brillo_update_payload verify
Change-Id: I850df7baf72fdd1f5b70b22506ebacadb60db58b