We have created a Macintosh file system library which is portable to a variety of operating systems and platforms. It presents a programming interface sufficient for creating a user level API as well as file system drivers for operating systems that support them. We implemented and tested such a user level API and utility programs based on it as well as an experimental Unix Virtual File System. We describe the Macintosh Hierarchical File System and our implementation and note that the design is

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... not well suited to reentrancy and that its complex data structures can lead to slow implementations in multiprogrammed environments. Performance measurements show that our implementation is faster than the native Macintosh implementation at creating, deleting, reading and writing files with small request sizes, but slower than the Berkeley Fast File System (FFS.) However, the native Macintosh implementation can perform large read and write operations faster that either our implementation or FFS.