The following revision refers to this bug:
  https://chromium.googlesource.com/aosp/platform/system/update_engine/+/ee6d9a1067175ab94de080feaf4db937eda43442

commit ee6d9a1067175ab94de080feaf4db937eda43442
Author: Amin Hassani <ahassani@google.com>
Date: Mon Sep 25 22:52:39 2017

update_engine: Add ExtentReader

Currently Each operation in DeltaPerformer has the responsibility of
reading from the source device by itself. Adding an
ExtentReader (similar to ExtentWriter) aggregates all these
responsibilities on DeltaPerformer.source_fd_. This simplifies the
design as each operation does not need to invent is own open/read/close
etc. This specially will be used in conjunction with bspatch and puffin.

BUG= chromium:761138 
TEST=FEATURES="test" emerge-amd64-generic update_engine;

Change-Id: I2c7a21a02bd1df06bbaa7ebf374a13f654768721
Reviewed-on: https://chromium-review.googlesource.com/651336
Commit-Ready: Amin Hassani <ahassani@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Andrew de los Reyes <adlr@chromium.org>
Reviewed-by: Sen Jiang <senj@chromium.org>

[modify] https://crrev.com/ee6d9a1067175ab94de080feaf4db937eda43442/update_engine.gyp
[modify] https://crrev.com/ee6d9a1067175ab94de080feaf4db937eda43442/Android.mk
[add] https://crrev.com/ee6d9a1067175ab94de080feaf4db937eda43442/payload_consumer/extent_reader.h
[add] https://crrev.com/ee6d9a1067175ab94de080feaf4db937eda43442/payload_consumer/extent_reader_unittest.cc
[add] https://crrev.com/ee6d9a1067175ab94de080feaf4db937eda43442/payload_consumer/extent_reader.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/aosp/platform/system/update_engine/+/db56be971d5c1adb405858e24ca772b5f3290099

commit db56be971d5c1adb405858e24ca772b5f3290099
Author: Amin Hassani <ahassani@google.com>
Date: Mon Sep 25 22:52:39 2017

update_engine: Use ExtentReader

Updates CopyAndHashExtents to use the new ExtentReader.

Adds CalculateAndValidatffeSourceHash() to DeltaPerformer to be used in both
SOURCE_BSDIFF and PUFFDIFF.

BUG= chromium:761138 
TEST=FEATURES="test" emerge-amd64-generic update_engine; brillo_update_payload verify

Change-Id: I2e0c10fe0078c5a1ab4cd646a91d42893b6b691b
Reviewed-on: https://chromium-review.googlesource.com/653478
Commit-Ready: Amin Hassani <ahassani@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>
Reviewed-by: Sen Jiang <senj@chromium.org>

[modify] https://crrev.com/db56be971d5c1adb405858e24ca772b5f3290099/payload_consumer/delta_performer.cc
[modify] https://crrev.com/db56be971d5c1adb405858e24ca772b5f3290099/payload_consumer/delta_performer.h
[modify] https://crrev.com/db56be971d5c1adb405858e24ca772b5f3290099/payload_consumer/file_descriptor_utils_unittest.cc
[modify] https://crrev.com/db56be971d5c1adb405858e24ca772b5f3290099/common/utils.h
[modify] https://crrev.com/db56be971d5c1adb405858e24ca772b5f3290099/payload_consumer/file_descriptor_utils.cc