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by asveikau
556 days ago
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The filesystem APIs for Windows and POSIX have extremely similar semantics when you bridge their superficial differences. I don't think this is as huge an achievement as suggested. Many multiplatform projects have similar wrapper layers. Indeed the FILE* abstraction in the C standard does some of it. (But not sufficient for the functionality that sqlite needs, hence the need for another wrapper.) That's not a knock on sqlite, I consider it well implemented and one of my favorite libraries I've ever seen, used and studied. |
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This is in part because Windows and POSIX are relatives. Windows is (partly) descended from DOS, and DOS 2 deliberately borrowed a lot of ideas from Xenix (Microsoft’s Unix port). And Windows has continued to borrow ideas from POSIX since, e.g. Winsock is heavily based on Berkeley Sockets.
Compare DOS 2+ handle-based IO to CP/M: CP/M treats files as fixed length 128 byte records instead of bytes, you can only read or write a whole record at a time, and a file’s size on disk must be a whole multiple of 128 [0] - that has more in common with mainframe/minicomputer record-oriented IO than Unix-style byte-oriented filesystems
[0] later on, CP/M added an attribute in the directory entry to store how many bytes were valid in the last record of a file; but it wasn’t actually enforced by the filesystem, apps had to set/get the attribute using a separate API, a lot of apps just ignored it, and even for those who did try to use it, two completely opposite conventions of how to use it coexisted