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pak_symbols.md

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Pak Symbols

Pak symbols are those with a section of:

  • .pak.nontranslated (entries in resources.pak, chrome_100_percent.pak)
  • .pak.translations (entries in en_US.pak, fr.pak, etc)
  • There is one symbols for each GRIT ID. The size of the symbol is the sum of the size of all pak entries with that ID across all .pak files.

Algorithm

During builds:

  • Grit records the originating .grd file, textual ID, and numeric ID for each entry that it processes during a grit() step into a .pak.info file.
  • These .pak.info files are merged during repack and APK / App Bundle steps into a single $output_dir/size-info/Foo.apk.pak.info.

During supersize archive:

  1. When native symbols are created using linker_map mode, a map of pak_id -> source_path is created by looking for symbols named ui::AllowlistedResource<$PAK_ID>().
  2. Pak files are extracted and turned into dicts using grit.
  3. The size of each pak entry is summed with other entries of the same ID.
  4. Symbol aliases are created for pak entries with different IDs, but that refer to the same data (the .pak file format supports this).
  5. Entry names ("textual IDs"), and the original .grd file paths are stored in the full_name of each symbol by using the information in the $outdir/size-info/Foo.pak.info file.
  6. Path information is added to the symbols using the map from Step 1.