tree 11b41e061ccf3f5b5d80790e47c1304be95d4457
parent 270524ffe9463e2d20fda43584d24cd84d4602df
author Sen Jiang <senj@google.com> 1536864176 -0700
committer Sen Jiang <senj@google.com> 1538600928 +0000

Support writing FEC.

After hash tree is written, we re-read the partition to encode FEC,
this cannot be done incrementally for each Update() like the hash
tree, because the data needed to encode each rs block are spreaded
across entire partition, and we can not afford to use that much
memory.

For each round, we encode block_size number of rs blocks, which will
produce block_size * fec_roots bytes of FEC data, this will allow us
to read one block at a time instead of one byte.

Bug: 28171891
Test: update_engine_unittests
Test: brillo_update_payload generate
Test: brillo_update_payload verify

Change-Id: I35ba7e0647b9ee5a97b972dc480deef60d813676