fsapi

Documentation

Index

• type File
  • func Adapt(f experimentalsys.File) File
• type Pflag

Types

type File

type File interface {
	experimentalsys.File

	// IsNonblock returns true if the file was opened with O_NONBLOCK, or
	// SetNonblock was successfully enabled on this file.
	//
	// # Notes
	//
	//   - This might not match the underlying state of the file descriptor if
	//     the file was not opened via OpenFile.
	IsNonblock() bool

	// SetNonblock toggles the non-blocking mode (O_NONBLOCK) of this file.
	//
	// # Errors
	//
	// A zero Errno is success. The below are expected otherwise:
	//   - ENOSYS: the implementation does not support this function.
	//   - EBADF: the file or directory was closed.
	//
	// # Notes
	//
	//   - This is like syscall.SetNonblock and `fcntl` with O_NONBLOCK in
	//     POSIX. See https://pubs.opengroup.org/onlinepubs/9699919799/functions/fcntl.html
	SetNonblock(enable bool) experimentalsys.Errno

	// Poll returns if the file has data ready to be read or written.
	//
	// # Parameters
	//
	// The `flag` parameter determines which event to await, such as POLLIN,
	// POLLOUT, or a combination like `POLLIN|POLLOUT`.
	//
	// The `timeoutMillis` parameter is how long to block for an event, or
	// interrupted, in milliseconds. There are two special values:
	//   - zero returns immediately
	//   - any negative value blocks any amount of time
	//
	// # Results
	//
	// `ready` means there was data ready to read or written. False can mean no
	// event was ready or `errno` is not zero.
	//
	// A zero `errno` is success. The below are expected otherwise:
	//   - ENOSYS: the implementation does not support this function.
	//   - ENOTSUP: the implementation does not the flag combination.
	//   - EINTR: the call was interrupted prior to an event.
	//
	// # Notes
	//
	//   - This is like `poll` in POSIX, for a single file.
	//     See https://pubs.opengroup.org/onlinepubs/9699919799/functions/poll.html
	//   - No-op files, such as those which read from /dev/null, should return
	//     immediately true, as data will never become available.
	//   - See /RATIONALE.md for detailed notes including impact of blocking.
	Poll(flag Pflag, timeoutMillis int32) (ready bool, errno experimentalsys.Errno)
}

File includes methods not yet ready to document for end users, notably non-blocking functionality.

Particularly, Poll is subject to debate. For example, whether a user should be able to choose how to implement timeout or not. Currently, this interface allows the user to choose to sleep or use native polling, and which choice they make impacts thread behavior as summarized here: https://github.com/tetratelabs/wazero/pull/1606#issuecomment-1665475516

func Adapt

func Adapt(f experimentalsys.File) File

type Pflag

type Pflag uint32

Pflag are bit flags used for File.Poll. Values, including zero, should not be interpreted numerically. Instead, use by constants prefixed with 'POLL'.

Notes

• This is like `pollfd.events` flags for `poll` in POSIX. See https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/poll.h.html

const (
	// POLLIN is a read event.
	POLLIN Pflag = 1 << iota

	// POLLOUT is a write event.
	POLLOUT
)

Only define bitflags we support and are needed by `poll_oneoff` in wasip1 See https://github.com/WebAssembly/WASI/blob/snapshot-01/phases/snapshot/docs.md#eventrwflags