[kangdaeun1022]

Summary

• centralize the string-equivalent checksum loop in MessageUtils
• reuse the allocation-free CharSequence path from Message#setChecksum and FieldMap#calculateChecksum
• preserve byte-based checksum calculation for multibyte charsets
• add regression coverage for the StringBuilder fast path, UTF-8 encoded bytes, and repeating-group checksum consistency

Optimization rationale

The shared helper accepts CharSequence, so Message#setChecksum operates directly on its existing StringBuilder without creating a String or byte[]. String-equivalent charsets continue to use direct character traversal, while non-string-equivalent charsets continue to calculate the checksum from encoded bytes.

Testing

• ./mvnw -pl quickfixj-base -Dtest=FieldMapTest,MessageUtilsTest test -Dmaven.javadoc.skip=true -PskipBundlePlugin (16 tests)
• ./mvnw -pl quickfixj-base test -Dmaven.javadoc.skip=true -PskipBundlePlugin (170 tests)

Fixes #1283

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.00%. Comparing base (db43e4d) to head (d4313d2).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1309      +/-   ##
============================================
+ Coverage     70.80%   71.00%   +0.19%     
- Complexity     2271     2276       +5     
============================================
  Files           161      161              
  Lines          9077     9073       -4     
  Branches       1192     1189       -3     
============================================
+ Hits           6427     6442      +15     
+ Misses         2197     2175      -22     
- Partials        453      456       +3     

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

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[the-thing]

Looks good.