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[api] Optimize protobuf decode loop for better performance and maintainability - #10277

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kbx81 merged 2 commits into
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decode_cleanup
Aug 18, 2025
Merged

[api] Optimize protobuf decode loop for better performance and maintainability#10277
kbx81 merged 2 commits into
devfrom
decode_cleanup

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@bdraco
@bdraco bdraco commented Aug 18, 2025
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What does this implement/fix?

Optimizes the protobuf decode loop in ProtoDecodableMessage::decode() by eliminating redundant error handling and improving control flow. The changes result in cleaner, more maintainable code with measurable performance improvements for typical API message sizes.

Key improvements:

  • Replaced error flag + break pattern with early returns, reducing branching overhead
  • Switched from index-based to pointer-based buffer traversal for better compiler optimization
  • Consolidated boundary checks for length-delimited fields
  • Improved error messages with offset reporting instead of index values
  • Reduced flash usage by 224 bytes with no RAM impact

Performance impact:

  • 7.5% faster for small messages (~100 bytes) - typical sensor updates
  • 1.2% faster for medium messages (~1KB) - device state messages
  • All ESPHome API messages are generally under 1400 bytes, so these improvements apply to all real-world usage
  • All improvements are statistically significant (p < 0.05)

Types of changes

  • Bugfix (non-breaking change which fixes an issue)
  • New feature (non-breaking change which adds functionality)
  • Breaking change (fix or feature that would cause existing functionality to not work as expected)
  • Code quality improvements to existing code or addition of tests
  • Other

Related issue or feature (if applicable):

  • Part of ongoing API performance optimization efforts

Pull request in esphome-docs with documentation (if applicable):

  • esphome/esphome-docs#

Test Environment

  • ESP32
  • ESP32 IDF
  • ESP8266
  • RP2040
  • BK72xx
  • RTL87xx
  • nRF52840

Example entry for config.yaml:

# No config changes required - internal optimization only
api:

Checklist:

  • The code change is tested and works locally.
  • Tests have been added to verify that the new code works (under tests/ folder).

If user exposed functionality or configuration variables are added/changed:

@github-actions
github-actions Bot commented Aug 18, 2025
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To use the changes from this PR as an external component, add the following to your ESPHome configuration YAML file:

external_components:
  - source: github://pr#10277
    components: [api]
    refresh: 1h

(Added by the PR bot)

@codecov-commenter
codecov-commenter commented Aug 18, 2025 •
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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.45%. Comparing base (daf8ec3) to head (a922714).
⚠️ Report is 4 commits behind head on dev.

Additional details and impacted files 
@@           Coverage Diff           @@
##              dev   #10277   +/-   ##
=======================================
  Coverage   60.45%   60.45%           
=======================================
  Files          51       51           
  Lines       10417    10417           
  Branches     1388     1388           
=======================================
  Hits         6298     6298           
  Misses       3760     3760           
  Partials      359      359

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

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@bdraco
bdraco marked this pull request as ready for review August 18, 2025 04:58
Copilot AI review requested due to automatic review settings August 18, 2025 04:58
@bdraco
bdraco requested a review from a team as a code owner August 18, 2025 04:58
Copilot AI reviewed Aug 18, 2025
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Pull Request Overview

This PR optimizes the protobuf decode loop in ProtoDecodableMessage::decode() by replacing error flag handling with early returns and switching from index-based to pointer-based buffer traversal. The changes improve performance by 1.2-7.5% for typical API message sizes while reducing flash usage by 224 bytes.

Key changes:

  • Replaced error flag + break pattern with immediate returns for cleaner control flow
  • Switched from array indexing to pointer arithmetic for better compiler optimization
  • Consolidated boundary checks and improved error messages with offset reporting

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Comment thread esphome/components/api/proto.cpp Outdated
Comment thread esphome/components/api/proto.cpp Outdated
Comment thread esphome/components/api/proto.cpp Outdated
Comment thread esphome/components/api/proto.cpp Outdated
Comment thread esphome/components/api/proto.cpp Outdated
Comment thread esphome/components/api/proto.cpp Outdated
@bdraco
bdraco marked this pull request as draft August 18, 2025 05:23
@bdraco
bdraco marked this pull request as ready for review August 18, 2025 13:31
kbx81
kbx81 approved these changes Aug 18, 2025
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Thanks! 🍻

@kbx81
kbx81 merged commit 44bd8e5 into dev Aug 18, 2025
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@kbx81
kbx81 deleted the decode_cleanup branch August 18, 2025 21:14
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