unicode: Use the correct maximum size of Cyrillic

[cosmo0920]

CP866 should be handled as the maximum byte is 3.

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Testing
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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

Summary by CodeRabbit

• Bug Fixes
  • Improved handling of Windows-encoded text characters to support wider character widths.

[coderabbitai]

📝 Walkthrough

Walkthrough

The PR updates the Windows-866 converter configuration in the Unicode handler by increasing the max_width field from 2 to 3. This single-line change affects how the converter reports its maximum character width for the Windows-866 encoding scheme.

Changes

Win866 Converter Configuration Update

Layer / File(s)	Summary
Win866 converter max_width adjustment src/unicode/flb_utf8_and_win.c	The win866_converter global variable increases its .max_width setting from 2 to 3.

Estimated Code Review Effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Poem

A rabbit hopped through encoding lands so wide,
Found win866 with max_width of pride,
From two to three, the change so neat,
Characters broader make the codec complete! 🐰✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: updating the maximum width for Cyrillic character handling in the unicode converter from 2 to 3 bytes.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch cosmo0920-correct-max-char-width

Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 Infer (1.2.0)

src/unicode/flb_utf8_and_win.c

src/unicode/flb_utf8_and_win.c:20:10: fatal error: 'fluent-bit/flb_log.h' file not found
20 | #include <fluent-bit/flb_log.h>
| ^~~~~~~~~~~~~~~~~~~~~~
1 error generated.
Error: the following clang command did not run successfully:
/opt/infer-linux-x86_64-v1.2.0/lib/infer/facebook-clang-plugins/clang/install/bin/clang-18
@/tmp/coderabbit-infer/7fe153dfd6d3458997130172f4e5b47504197275-e27c65e894c60c01/tmp/clang_command_.tmp.84cae5.txt
++Contents of '/tmp/coderabbit-infer/7fe153dfd6d3458997130172f4e5b47504197275-e27c65e894c60c01/tmp/clang_command_.tmp.84cae5.txt':
"-cc1" "-load"
"/opt/infer-linux-x86_64-v1.2.0/lib/infer/infer/bin/../../facebook-clang-plugins/libtooling/build/FacebookClangPlugin.dylib"
"-add-plugin" "BiniouASTExporter" "-plugin-arg-BiniouASTExporter" "-"
"-plugin-arg-BiniouASTExporter" "PREPEND_CURRENT_DIR=1"
"-plugin-arg-BiniouASTExporter" "MAX_STRING_SIZE=65535" "-cc1" "-triple"
"x86_64-unknown-linux-gnu" "-emit-obj" "-

... [truncated 744 characters] ...

inux-x86_64-v1.2.0/lib/infer/facebook-clang-plugins/clang/install/lib/clang/18/include"
"-internal-isystem" "/usr/local/include" "-internal-isystem"
"/usr/lib/gcc/x86_64-linux-gnu/12/../../../../x86_64-linux-gnu/include"
"-internal-externc-isystem" "/usr/include/x86_64-linux-gnu"
"-internal-externc-isystem" "/include" "-internal-externc-isystem"
"/usr/include" "-Wno-ignored-optimization-argument" "-Wno-everything"
"-ferror-limit" "19" "-fgnuc-version=4.2.1" "-fskip-odr-check-in-gmf"
"-D__GCC_HAVE_DWARF2_CFI_ASM=1" "-o"
"/tmp/coderabbit-infer/e27c65e894c60c01/file.o" "-x" "c"
"src/unicode/flb_utf8_and_win.c" "-O0" "-fno-builtin" "-include"
"/opt/infer-linux-x86_64-v1.2.0/lib/infer/infer/bin/../lib/clang_wrappers/global_defines.h"
"-Wno-everything"

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[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@src/unicode/flb_utf8_and_win.c`:
- Line 121: Update the CP866 converter's max UTF-8 byte width to 3 by setting
the win866_converter's .max_width field to 3 (replacing the previous 2) to
prevent buffer overflows for U+2500–U+257F box-drawing and similar characters;
ensure this matches the other Windows codepage converters (e.g., the converters
defined near the .max_width entries at lines with win1250_converter,
win1251_converter, etc.), run the unicode conversion tests, and adjust any
related buffer allocation logic/comments to reflect the 3-byte UTF-8 maximum.
- Line 121: Add targeted CP866 (Win866) box-drawing coverage: extend
tests/internal/unicode.c to include test vectors covering CP866 bytes 0xB0–0xDF
mapped to U+2500+ (box-drawing) and assert correct UTF-8 conversion and
round-trip via the conversion routines used in src/unicode/flb_utf8_and_win.c
(locate the encoder/decoder functions in that file and any helpers that
reference the .max_width setting). Update
tests/runtime/data/tail/generate_generic_encoder_testing_data.py to emit the
same CP866 sequences so CI-generated test data includes box-drawing chars. After
adding tests, run Valgrind (or equivalent) against the new test suite focusing
on the conversion path to ensure no memory corruption/leaks and fix any issues
found; consider preparing the change as a backport candidate for Windows
codepage conversion safety.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 54ef58ad-51b6-4bc6-bc59-c58f92d0c45c

📥 Commits

Reviewing files that changed from the base of the PR and between 5880717 and 7fe153d.

📒 Files selected for processing (1)

• src/unicode/flb_utf8_and_win.c