Call native C and C++ shared libraries from JavaScript using Bun's FFI API.
npx skills add https://github.com/aicodepro/ai-agent-nexi --skill bun-ffi-aicodepro
Please help me install this Agent Skill. Skill: bun-ffi Source: https://github.com/aicodepro/ai-agent-nexi/tree/main/agent/skills/bun-ffi Command: npx skills add https://github.com/aicodepro/ai-agent-nexi --skill bun-ffi-aicodepro
bun:ffi module to load shared libraries and call native functions without any compilation toolchain. ## Core Features & Use Cases - Library Loading: Load system or custom shared libraries (.dll, .so, .dylib) with cross-platform path resolution using dlopen and suffix. - Type Mapping & Function Definitions: Map C types (integers, floats, pointers, cstrings) to FFIType definitions and declare function signatures with arguments and return types. - Memory & Pointer Operations: Work with pointers, ArrayBuffers, structs, and C strings using ptr, CString, and toArrayBuffer. - Callbacks: Pass JavaScript functions as C callbacks for operations like custom sort comparators. - Use Case: Call SQLite's C API directly from a Bun script to open a database, execute SQL, and close the connection without any ORM or native addon. ## Quick Start Show me how to call a function from a native C shared library in Bun using bun:ffi with dlopen and FFIType definitions.High-intent search queries and answers about installing and using this skill.
Use dlopen from bun:ffi to load the shared library and declare the function signature with FFIType argument and return types. Then invoke it via lib.symbols.functionName with matching arguments.
Convert the string to a null-terminated Buffer with Buffer.from("text\0") and pass it using ptr(). For strings returned from C, wrap the pointer in new CString(result) to convert it back to a JavaScript string.
Yes, bun:ffi is cross-platform. Use the exported suffix value to resolve the correct library extension: dll on Windows, so on Linux, and dylib on macOS, then build platform-specific paths as needed.
Segmentation faults usually come from invalid pointers, wrong FFIType declarations that mismatch the actual C signature, or accessing freed memory. Verify that argument and return types exactly match the C header definitions.
Yes, use the callback function from bun:ffi to wrap a JavaScript function with a C-compatible signature, then pass its ptr to the native function. Call close() on the callback when finished to release resources.
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