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Make some improvements of little consequence

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Justine Tunney 2024-07-27 08:20:18 -07:00
parent 690d3df66e
commit 18a620cc1a
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11 changed files with 92 additions and 14 deletions
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57
libc/calls/statfs.c
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@ -34,6 +34,63 @@
/**
* Returns information about filesystem.
*
* The `struct statfs` returned has the following fields:
*
* - `f_fstypename` holds a NUL-terminated string identifying the file
* system type. On Linux, this will usually be "nfs". On FreeBSD, it
* will usually be "zfs". On OpenBSD and NetBSD, it's usually "ffs".
* On MacOS it's usually "apfs", and on Windows it's usually "NTFS".
*
* - `f_bsize` is the optimal transfer block size. This may be used to
* appropriately chunk your i/o operations. On local file systems it
* will usually be somewhere between 4096 and 131072 bytes. With NFS
* it may be as high as 512kb.
*
* - `f_frsize` is the fragment size of the file system. This could be
* anywhere between 512 and 4096 bytes for local filesystems usually
* although it could go higher. It should less than, or equal to the
* `f_bsize`. This fragment size is what you want to use to multiply
* other fields that count blocks into a byte count.
*
* - `f_bfree` is the number of free blocks in the filesystem. You can
* multiply this number by `f_frsize` to obtain the free byte count.
*
* - `f_bavail` is the number of free blocks in the filesystem you can
* access from userspace. It's less than or equal to `f_bfree` which
* generally has some blocks reserved for root in a pinch. You could
* multiply this by `f_frsize` to convert this number to bytes.
*
* - `f_files` is the total number of file nodes. Not every OS has it.
* On Windows for instance it's currently always `INT64_MAX`. It has
* an unspecified meaning. It should be seen as informative.
*
* - `f_fsid` is an opaque data structure that uniquely identifies the
* filesystem. We're not yet certain how reliable this is across the
* various OSes and filesystem types.
*
* - `f_namelen` is basically the same as `NAME_MAX` which seems to be
* 255 on all the OSes we've evaluated. It's the maximum length when
* it comes to individual components in a filesystem path.
*
* - `f_type` is an OS-specific file system type ID. This is just some
* magic number. No defines are provided by Cosmopolitan Libc for it
*
* - `f_flags` specifies the options used when a filesystem is mounted
* and the numbers vary across OSes. Cosmopolitan Libc polyfills the
* magic numbers somewhat consistently. If `IsWindows()` is set then
* the constants defined by Microsoft (e.g. `FILE_READ_ONLY_VOLUME`)
* should be used. Otherwise on any other UNIX system, the following
* constants are provided. You should check each constant at runtime
* before using them, to determine if they're non-zero, for support.
*
* - `ST_RDONLY` if mounted in read-only mode (works UNIX + Windows)
* - `ST_NOSUID` if setuid binaries are forbidden (all UNIX support)
* - `ST_NODEV` when device file access forbidden (all UNIX support)
* - `ST_NOEXEC` when a file executions forbidden (all UNIX support)
* - `ST_SYNCHRONOUS`, if `O_SYNC` always happens (all UNIX support)
* - `ST_NOATIME` if access timestamps aren't set (all UNIX support)
* - `ST_RELATIME` if relative acces time is used (all UNIX support)
*
* @return 0 on success, or -1 w/ errno
* @raise ECANCELED if thread was cancelled in masked mode
* @raise EINTR if signal was delivered