wrapper (thing)

A wrapper is a driver stub that emulates some API library and converts them to calls to another driver's API.
The common issues with such drivers are:

1. API calls are seldom mappable 1-to-1. That forces unwanted complexity and performance hit compared to the target driver or the emulated one, and introduces reliability problems.
2. When wrappers are custom-made to support certain applications, they neglect to implement API calls which are not used by the targeted application; The wrapper is then unsuitable for any other purpose.
3. By perpetuating support for deprecated APIs; they stall re-engineering of existing applications using the older APIs and stifle adoption of newer APIs.

Example of wrappers:

• VFWWDM: Provide Video for Windows API support for Video Capture hardware implemented using newer Windows Driver Model API (Issue #1,#3)
• GLiDE: Provide emulation of 3DFX API to newer 3D video cards that now use OpenGL or Direct3D. Most are custom-made to support UltraHLE (issue #2)
• DB-Library : Provide support for legacy MS-SQL and SYBASE applications by converting database interface calls to Sybase's newer CT-Library API set. (#3)