;; WASI I/O.
;;
;; Some content here is derived from [CloudABI](https://github.com/NuxiNL/cloudabi).
;;
;; This is a `witx` file. See [here](https://github.com/WebAssembly/WASI/tree/master/docs/witx.md)
;; for an explanation of what that means.

(use "typenames.witx")

(module $wasi_ephemeral_fd
  ;;; Linear memory to be accessed by WASI functions that need it.
  (import "memory" (memory))

  ;;; Provide file advisory information on a file descriptor.
  ;;; Note: This is similar to `posix_fadvise` in POSIX.
  (@interface func (export "advise")
    (param $fd $fd)
    ;;; The offset within the file to which the advisory applies.
    (param $offset $filesize)
    ;;; The length of the region to which the advisory applies.
    (param $len $filesize)
    ;;; The advice.
    (param $advice $advice)
    (result $error $errno)
  )

  ;;; Force the allocation of space in a file.
  ;;; Note: This is similar to `posix_fallocate` in POSIX.
  (@interface func (export "allocate")
    (param $fd $fd)
    ;;; The offset at which to start the allocation.
    (param $offset $filesize)
    ;;; The length of the area that is allocated.
    (param $len $filesize)
    (result $error $errno)
  )

  ;;; Close a file descriptor.
  ;;; Note: This is similar to `close` in POSIX.
  (@interface func (export "close")
    (param $fd $fd)
    (result $error $errno)
  )

  ;;; Synchronize the data of a file to disk.
  ;;; Note: This is similar to `fdatasync` in POSIX.
  (@interface func (export "datasync")
    (param $fd $fd)
    (result $error $errno)
  )

  ;;; Get the attributes of a file descriptor.
  ;;; Note: This returns similar flags to `fsync(fd, F_GETFL)` in POSIX, as well as additional fields.
  (@interface func (export "fdstat_get")
    (param $fd $fd)
    (result $error $errno)
    ;;; The buffer where the file descriptor's attributes are stored.
    (result $stat $fdstat)
  )

  ;;; Adjust the flags associated with a file descriptor.
  ;;; Note: This is similar to `fcntl(fd, F_SETFL, flags)` in POSIX.
  (@interface func (export "fdstat_set_flags")
    (param $fd $fd)
    ;;; The desired values of the file descriptor flags.
    (param $flags $fdflags)
    (result $error $errno)
  )

  ;;; Adjust the rights associated with a file descriptor.
  ;;; This can only be used to remove rights, and returns `errno::notcapable` if called in a way that would attempt to add rights
  (@interface func (export "fdstat_set_rights")
    (param $fd $fd)
    ;;; The desired rights of the file descriptor.
    (param $fs_rights_base $rights)
    (param $fs_rights_inheriting $rights)
    (result $error $errno)
  )

  ;;; Return the attributes of an open file.
  (@interface func (export "filestat_get")
    (param $fd $fd)
    (result $error $errno)
    ;;; The buffer where the file's attributes are stored.
    (result $buf $filestat)
  )

  ;;; Adjust the size of an open file. If this increases the file's size, the extra bytes are filled with zeros.
  ;;; Note: This is similar to `ftruncate` in POSIX.
  (@interface func (export "filestat_set_size")
    (param $fd $fd)
    ;;; The desired file size.
    (param $size $filesize)
    (result $error $errno)
  )

  ;;; Adjust the timestamps of an open file or directory.
  ;;; Note: This is similar to `futimens` in POSIX.
  (@interface func (export "filestat_set_times")
    (param $fd $fd)
    ;;; The desired values of the data access timestamp.
    (param $atim $timestamp)
    ;;; The desired values of the data modification timestamp.
    (param $mtim $timestamp)
    ;;; A bitmask indicating which timestamps to adjust.
    (param $fst_flags $fstflags)
    (result $error $errno)
  )

  ;;; Set the permissions of a file or directory.
  ;;;
  ;;; This sets the permissions associated with a file or directory in
  ;;; a filesystem at the time it is called. The ability to actually access
  ;;; a file or directory may depend on additional permissions not reflected
  ;;; here.
  ;;;
  ;;; Note: This is similar `fchmod` in POSIX.
  ;;;
  ;;; Unlike POSIX, this doesn't expose a user/group/other distinction;
  ;;; implementations in POSIX environments are suggested to consult the
  ;;; umask to determine which of the user/group/other flags to modify.
  (@interface func (export "permissions_set")
    (param $fd $fd)
    ;;; The permissions associated with the file.
    (param $permissions $permissions)
    (result $error $errno)
  )

  ;;; Read from a file descriptor, without using and updating the file descriptor's offset.
  ;;; Note: This is similar to `preadv` in POSIX.
  (@interface func (export "pread")
    (param $fd $fd)
    ;;; List of scatter/gather vectors in which to store data.
    (param $iovs $iovec_array)
    ;;; The offset within the file at which to read.
    (param $offset $filesize)
    (result $error $errno)
    ;;; The number of bytes read.
    (result $nread $size)
  )

  ;;; Return a description of the given preopened file descriptor.
  (@interface func (export "prestat_get")
    (param $fd $fd)
    (result $error $errno)
    ;;; The buffer where the description is stored.
    (result $buf $prestat)
  )

  ;;; Return a description of the given preopened file descriptor.
  (@interface func (export "prestat_dir_name")
    (param $fd $fd)
    ;;; A buffer into which to write the preopened directory name.
    (param $path (@witx pointer char8))
    (param $path_len $size)
    (result $error $errno)
  )

  ;;; Write to a file descriptor, without using and updating the file descriptor's offset.
  ;;; Note: This is similar to `pwritev` in POSIX.
  (@interface func (export "pwrite")
    (param $fd $fd)
    ;;; List of scatter/gather vectors from which to retrieve data.
    (param $iovs $ciovec_array)
    ;;; The offset within the file at which to write.
    (param $offset $filesize)
    (result $error $errno)
    ;;; The number of bytes written.
    (result $nwritten $size)
  )

  ;;; Read from a file descriptor.
  ;;; Note: This is similar to `readv` in POSIX.
  (@interface func (export "read")
    (param $fd $fd)
    ;;; List of scatter/gather vectors to which to store data.
    (param $iovs $iovec_array)
    (result $error $errno)
    ;;; The number of bytes read.
    (result $nread $size)
  )

  ;;; Read directory entries from a directory.
  ;;; When successful, the contents of the output buffer consist of a sequence of
  ;;; directory entries. Each directory entry consists of a `dirent` object,
  ;;; followed by `dirent::d_namlen` bytes holding the name of the directory
  ;;; entry.
  ;;
  ;;; This function fills the output buffer as much as possible, potentially
  ;;; truncating the last directory entry. This allows the caller to grow its
  ;;; read buffer size in case it's too small to fit a single large directory
  ;;; entry, or skip the oversized directory entry.
  (@interface func (export "readdir")
    (param $fd $fd)
    ;;; The buffer where directory entries are stored
    (param $buf (@witx pointer u8))
    (param $buf_len $size)
    ;;; The location within the directory to start reading
    (param $cookie $dircookie)
    (result $error $errno)
    ;;; The number of bytes stored in the read buffer. If less than the size of the read buffer, the end of the directory has been reached.
    (result $bufused $size)
  )

  ;;; Atomically replace a file descriptor by renumbering another file descriptor.
  ;;
  ;;; Due to the strong focus on thread safety, this environment does not provide
  ;;; a mechanism to duplicate or renumber a file descriptor to an arbitrary
  ;;; number, like `dup2()`. This would be prone to race conditions, as an actual
  ;;; file descriptor with the same number could be allocated by a different
  ;;; thread at the same time.
  ;;
  ;;; This function provides a way to atomically renumber file descriptors, which
  ;;; would disappear if `dup2()` were to be removed entirely.
  (@interface func (export "renumber")
    (param $fd $fd)
    ;;; The file descriptor to overwrite.
    (param $to $fd)
    (result $error $errno)
  )

  ;;; Move the offset of a file descriptor.
  ;;; Note: This is similar to `lseek` in POSIX.
  (@interface func (export "seek")
    (param $fd $fd)
    ;;; The number of bytes to move.
    (param $offset $filedelta)
    ;;; The base from which the offset is relative.
    (param $whence $whence)
    (result $error $errno)
    ;;; The new offset of the file descriptor, relative to the start of the file.
    (result $newoffset $filesize)
  )

  ;;; Synchronize the data and metadata of a file to disk.
  ;;; Note: This is similar to `fsync` in POSIX.
  (@interface func (export "sync")
    (param $fd $fd)
    (result $error $errno)
  )

  ;;; Return the current offset of a file descriptor.
  ;;; Note: This is similar to `lseek(fd, 0, SEEK_CUR)` in POSIX.
  (@interface func (export "tell")
    (param $fd $fd)
    (result $error $errno)
    ;;; The current offset of the file descriptor, relative to the start of the file.
    (result $offset $filesize)
  )

  ;;; Write to a file descriptor.
  ;;; Note: This is similar to `writev` in POSIX.
  (@interface func (export "write")
    (param $fd $fd)
    ;;; List of scatter/gather vectors from which to retrieve data.
    (param $iovs $ciovec_array)
    (result $error $errno)
    ;;; The number of bytes written.
    (result $nwritten $size)
  )
)