rawio
import "toolman.org/io/rawio"
Overview
Package rawio provides utilities for performing cancellable I/O operations.
Install
go get toolman.org/io/rawioIndex
Package files
epoll.go fd.go latch.go reader.go
Variables
var ErrNoFD = errors.New("no manner to discern file descriptor from object")ErrNoFD indicates that no file descriptor could be extracted.
var NotifySignal = syscall.SIGIONotifySignal is the signal that will be used to interrupt a blocked Read operation.
func ExtractFD
func ExtractFD(x interface{}) (int, error)ExtractFD attempts to extract a usable file descriptor from x -- which must be either an *os.File or an object with a method having a signature of "File() (*os.File, error)", such as most implementations of net.Conn. If x is something else, ErrNoFD is returned.
If x is an *os.File, its Fd method is called -- otherwise, an *os.File is aquired from the aforementioned File method and its Fd method is called. In either case, a file descriptor is acquired then duped and the duplicate file descriptor is returned.
Prior to returning, Close is called on the *os.File used to acquire the original file descriptor and, if x is not an *os.File but is an io.Closer, x will also be closed. If any of these close operations result in an error, the duped file descriptor is also closed and an error is returned.
On success, a usable file descriptor and a nil error are returned and the object from which it was extracted will be closed and no longer usable.
Note: We dupe the file descriptor before returning it because os.File has a finalizer routine which calls Close when the object is garbage collected. This also closes the file descriptor returned by its Fd method.
Deprecated: With the advent of the syscall.RawConn interface introduced in Go v1.12, ExtractFD is no longer necessary.
func IsEAGAIN
func IsEAGAIN(err error) boolIsEAGAIN returns true if err represents a system error indicating that an operation should be tried again.
type RawReader
type RawReader struct {
sync.RWMutex
// contains filtered or unexported fields
}A RawReader performs read operations that may be cancelled -- either by closing the reader from a separate goroutine or, through its ReadContext method, if the context is cancelled.
func NewRawReader
func NewRawReader(fd int) (*RawReader, error)NewRawReader creates a new RawReader from fd or nil and an error if the RawReader cannot be created.
func (*RawReader) Close
func (r *RawReader) Close() errorClose will close the RawReader. Any concurrently blocked read operations will return io.EOF. Close implements io.Closer.
func (*RawReader) Fd
func (r *RawReader) Fd() intFd returns the file descriptor assocated with this RawReader.
func (*RawReader) Read
func (r *RawReader) Read(p []byte) (int, error)Read implements io.Reader. If Read is blocked and r is closed in a separate goroutine, Read will return 0 and io.EOF.
func (*RawReader) ReadContext
func (r *RawReader) ReadContext(ctx context.Context, p []byte) (int, error)ReadContext behaves similar to Read but may also be cancelled through the given context. If ctx is cancelled, then ReadContext will return ctx.Err().