FFI Design

Expert skill for designing and implementing foreign function interfaces to native code

509 stars

bya5c-ai

View on GitHub Installation ↓

Best use case

FFI Design is best used when you need a repeatable AI agent workflow instead of a one-off prompt.

Expert skill for designing and implementing foreign function interfaces to native code

Teams using FFI Design should expect a more consistent output, faster repeated execution, less prompt rewriting.

When to use this skill

You want a reusable workflow that can be run more than once with consistent structure.

When not to use this skill

You only need a quick one-off answer and do not need a reusable workflow.
You cannot install or maintain the underlying files, dependencies, or repository context.

Installation

Claude Code / Cursor / Codex

$curl -o ~/.claude/skills/ffi-design/SKILL.md --create-dirs "https://raw.githubusercontent.com/a5c-ai/babysitter/main/library/specializations/programming-languages/skills/ffi-design/SKILL.md"

Manual Installation

Download SKILL.md from GitHub
Place it in .claude/skills/ffi-design/SKILL.md inside your project
Restart your AI agent — it will auto-discover the skill

How FFI Design Compares

Feature / Agent	FFI Design	Standard Approach
Platform Support	Not specified	Limited / Varies
Context Awareness	High	Baseline
Installation Complexity	Unknown	N/A

Frequently Asked Questions

What does this skill do?

Expert skill for designing and implementing foreign function interfaces to native code

Where can I find the source code?

You can find the source code on GitHub using the link provided at the top of the page.

SKILL.md Source

# FFI Design Skill

## Overview

Expert skill for designing and implementing foreign function interfaces to native code.

## Capabilities

- Design FFI declaration syntax
- Implement type marshaling between languages
- Handle C calling conventions (cdecl, stdcall, fastcall)
- Implement callback support (native calling managed)
- Handle string encoding conversions
- Implement struct layout matching (padding, alignment)
- Design memory ownership transfer rules
- Support dynamic library loading

## Target Processes

- ffi-implementation.js
- interpreter-implementation.js
- bytecode-vm-implementation.js
- code-generation-llvm.js

## Dependencies

- libffi
- Platform ABI documentation

## Usage Guidelines

1. **Safety**: Design safe wrappers around unsafe FFI calls
2. **Marshaling**: Document type marshaling rules explicitly
3. **Ownership**: Make memory ownership clear at FFI boundaries
4. **Callbacks**: Handle callback lifetimes carefully
5. **Strings**: Handle string encoding conversions correctly (UTF-8, UTF-16)

## Output Schema

```json
{
  "type": "object",
  "properties": {
    "callingConventions": {
      "type": "array",
      "items": { "type": "string" }
    },
    "marshalingRules": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "sourceType": { "type": "string" },
          "targetType": { "type": "string" }
        }
      }
    },
    "callbackSupport": { "type": "boolean" },
    "generatedFiles": {
      "type": "array",
      "items": { "type": "string" }
    }
  }
}
```

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