Add string_truncate utility function

[devin-ai-integration]

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Summary

Adds a new string_truncate utility function to the common library that truncates strings to a maximum length with ellipsis ("...") appended when truncation occurs.

Changes

• Added string_truncate(const std::string & str, size_t max_len) function to common/common.cpp
• Added corresponding declaration to common/common.h
• Added comprehensive Doxygen documentation with @brief, @param, @return, @note, and @example tags

Behavior

• Returns original string if length <= max_len
• If max_len < 3, returns truncated string without ellipsis
• Otherwise, returns first (max_len - 3) characters + "..."

Updates Since Last Revision

• Added Doxygen-style documentation for the function per reviewer request

Human Review Checklist

• Remove test comment: There's a ##testing if devin picks up changes line at the top of common/common.cpp that appears to be a test artifact and should be removed before merge
• Verify this function will be used (currently not called anywhere)
• Consider UTF-8 multi-byte character handling - current implementation may truncate in the middle of a multi-byte character (documented in @note)
• Consider adding unit tests for edge cases

---

Link to Devin run: https://app.devin.ai/sessions/5e245aad12d74691a4288601a0c20619
Requested by: Jake Cosme (jake@cognition.ai) (@jakexcosme)

[devin-ai-integration]

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[devin-ai-integration]

API Consistency Issue: The function signature uses const std::string & while similar string utility functions in this same file use std::string_view:

// Existing functions use string_view:
bool string_ends_with(const std::string_view & str, const std::string_view & suffix);
bool string_remove_suffix(std::string & str, const std::string_view & suffix);
size_t string_find_partial_stop(const std::string_view & str, const std::string_view & stop);

// New function uses string:
std::string string_truncate(const std::string & str, size_t max_len);

Recommendation: For consistency with the existing codebase conventions and to avoid forcing callers to materialize a std::string when they have a string_view or string literal, consider changing the signature to:

std::string string_truncate(std::string_view str, size_t max_len);

Additionally, since the PR description already notes the UTF-8 truncation concern, it would be helpful to clarify in the doc comment that max_len is a byte count, not a character count. For example:

// Truncate a string to a maximum byte length, adding ellipsis if truncated

This makes the behavior explicit and avoids surprising callers who might expect character-based truncation.

[jakexcosme]

Devin - add something similar to docstrings for this change so we can understand what was added

[devin-ai-integration]

Done! I've added Doxygen-style documentation for the string_truncate function including:

• @brief description
• @param documentation for both parameters
• @return documentation explaining all return cases
• @note about UTF-8 byte-level operation
• @example with usage examples

See commit c5e26d4.

[devin-ai-integration]

Build Blocker: This line is not valid C++ syntax and will cause compilation to fail with an error like stray '##' in program.

This appears to be a test comment that should be removed before merging. If you intended to add a comment, use // for single-line comments:

// testing if devin picks up changes

Or simply remove this line entirely since it seems to be for testing purposes only.

[devin-ai-integration]

Build Error: This line causes a compilation failure:

/home/ubuntu/repos/llama.cpp/common/common.cpp:1:1: error: stray '##' in program
    1 | ##testing if devin picks up changes
      | ^~
/home/ubuntu/repos/llama.cpp/common/common.cpp:1:3: error: 'testing' does not name a type

## is not a valid C++ comment syntax. This appears to be a test artifact that must be removed before merge. Use // for single-line comments or /* */ for multi-line comments in C++.

[devin-ai-integration]

Code Convention: Consider using std::string_view instead of const std::string & for consistency with nearby string utility functions in this file.

For example, string_ends_with and string_find_partial_stop (lines 586-588 in common.h) already use std::string_view:

bool string_ends_with(const std::string_view & str, const std::string_view & suffix);
size_t string_find_partial_stop(const std::string_view & str, const std::string_view & stop);

Suggested change:

std::string string_truncate(std::string_view str, size_t max_len);

This avoids forcing callers to allocate a std::string just to truncate, and maintains consistency with the existing API style in this module.