toolman.org/io/rawio

rawio

import "toolman.org/io/rawio"

• Overview
• Index

Overview

Package rawio provides utilities for performing cancellable I/O operations.

Install

  go get toolman.org/io/rawio

Index

• Variables
• func ExtractFD(x interface{}) (int, error)
• func IsEAGAIN(err error) bool
• type RawReader
  • func NewRawReader(fd int) (*RawReader, error)
  • func (r *RawReader) Close() error
  • func (r *RawReader) Fd() int
  • func (r *RawReader) Read(p []byte) (int, error)
  • func (r *RawReader) ReadContext(ctx context.Context, p []byte) (int, error)

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.SIGIO

NotifySignal 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.

func IsEAGAIN

func IsEAGAIN(err error) bool

IsEAGAIN 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() error

Close will close the RawReader. Any concurrently blocked read operations will return io.EOF. Close implements io.Closer.

func (*RawReader) Fd

func (r *RawReader) Fd() int

Fd 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().