blob: 1adf6d2af577f28a9d2b8c09b05f330277e152d1 [file] [log] [blame]
.. _module-pw_protobuf-size_report:
pw_protobuf extended size report
pw_protobuf can impact binary size very differently depending on how it's used.
A series of examples are provided below to illustrate how much certain use cases
affect binary size.
This module includes a proto encoder, two different proto decoders (one that
operates on a ``pw::stream::StreamReader`` and another that operates on an in-
memory buffer), codegen for direct wire-format encoders/decoders, and a
table-based codegen system for constructing proto messages as in-memory structs.
Here's a brief overview of the different encoder/decoder costs:
.. include:: size_report/protobuf_overview
.. note::
There's some overhead involved in ensuring all of the encoder/decoder
functionality is pulled in. Check the per-symbol breakdown for more details.
Encoder/decoder codegen overhead
The different proto serialization/deserialization codegen methods have different
overhead. Some have a higher up-front cost, but lower complexity (and therefore
smaller compiler generated code) at the sites of usage. Others trade lower
up-front code size cost for more complexity at the proto construction and read
This example uses the following proto message to construct a variety of use
cases to illustrate how code and memory requirements can change depending on
the complexity of the proto message being encoded/decoded.
.. literalinclude:: pw_protobuf_test_protos/size_report.proto
:language: protobuf
:lines: 14-
This proto is configured with the following options file:
.. literalinclude:: pw_protobuf_test_protos/size_report.options
:lines: 14-
Trivial proto
This is a size report for encoding/decoding the ``pw.protobuf.test.ItemInfo``
message. This is a pretty trivial message with just a few integers.
.. include:: size_report/simple_codegen_size_comparison
Optional and oneof
This is a size report for encoding/decoding the
``pw.protobuf.test.ResponseInfo`` message. This is slightly more complex message
that has a few explicitly optional fields, a oneof, and a submessage.
.. include:: size_report/oneof_codegen_size_comparison