trace_processor: clean up SystraceParser

The systrace line parser accumulated too much technical debt
and became a source of bugs. Refactor it to keep more readable.
Deliberate behavioral changes:
- Don't parse the counter value as double. ctrace seems to
  support only int values. Double can lose precision with
  pointers or anything larger than 2**53.
- Relax the parsing of "category groups" for counters, allow
  parsing of "C|543|foo|". We ignore the last arg anyways.

Also fix a borderline behavior I spotted in StringView. When
constructing a StringView(end(), 0), data_ is NOT nullptr even
though the string is empty. For that case, when calling
ToStdString() check the size_ not data_ nullity. data_ nullity
relies on std::string ctor to have a defined behavior when
calling std::string(out_of_bounds_ptr, 0). I couldn't find
any confirmation about this.

Change-Id: Ied7cd806c7f740e2cfad5e1854f956e1e4b4ef72
Bug: 189804795
5 files changed
tree: 68014bfc19156f5d88f974d8de3ebbdb08cf9d34
  1. .github/
  2. bazel/
  3. build_overrides/
  4. buildtools/
  5. debian/
  6. docs/
  7. examples/
  8. gn/
  9. include/
  10. infra/
  11. protos/
  12. src/
  13. test/
  14. tools/
  15. ui/
  16. .clang-format
  17. .clang-tidy
  18. .gitattributes
  19. .gitignore
  20. .gn
  21. .style.yapf
  22. Android.bp
  23. Android.bp.extras
  24. BUILD
  25. BUILD.extras
  26. BUILD.gn
  27. CHANGELOG
  28. codereview.settings
  29. DIR_METADATA
  30. heapprofd.rc
  31. LICENSE
  32. meson.build
  33. METADATA
  34. MODULE_LICENSE_APACHE2
  35. OWNERS
  36. perfetto.rc
  37. PerfettoIntegrationTests.xml
  38. PRESUBMIT.py
  39. README.chromium
  40. README.md
  41. TEST_MAPPING
  42. traced_perf.rc
  43. WORKSPACE
README.md

Perfetto - System profiling, app tracing and trace analysis

Perfetto is a production-grade open-source stack for performance instrumentation and trace analysis. It offers services and libraries and for recording system-level and app-level traces, native + java heap profiling, a library for analyzing traces using SQL and a web-based UI to visualize and explore multi-GB traces.

See https://perfetto.dev/docs or the /docs/ directory for documentation.