fd_plan9.go

Documentation: internal/poll

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package poll
     6  
     7  import (
     8  	"errors"
     9  	"io"
    10  	"sync"
    11  	"time"
    12  )
    13  
    14  type FD struct {
    15  	// Lock sysfd and serialize access to Read and Write methods.
    16  	fdmu fdMutex
    17  
    18  	Destroy func()
    19  
    20  	// deadlines
    21  	rmu       sync.Mutex
    22  	wmu       sync.Mutex
    23  	raio      *asyncIO
    24  	waio      *asyncIO
    25  	rtimer    *time.Timer
    26  	wtimer    *time.Timer
    27  	rtimedout bool // set true when read deadline has been reached
    28  	wtimedout bool // set true when write deadline has been reached
    29  
    30  	// Whether this is a normal file.
    31  	// On Plan 9 we do not use this package for ordinary files,
    32  	// so this is always false, but the field is present because
    33  	// shared code in fd_mutex.go checks it.
    34  	isFile bool
    35  }
    36  
    37  // We need this to close out a file descriptor when it is unlocked,
    38  // but the real implementation has to live in the net package because
    39  // it uses os.File's.
    40  func (fd *FD) destroy() error {
    41  	if fd.Destroy != nil {
    42  		fd.Destroy()
    43  	}
    44  	return nil
    45  }
    46  
    47  // Close handles the locking for closing an FD. The real operation
    48  // is in the net package.
    49  func (fd *FD) Close() error {
    50  	if !fd.fdmu.increfAndClose() {
    51  		return errClosing(fd.isFile)
    52  	}
    53  	return nil
    54  }
    55  
    56  // Read implements io.Reader.
    57  func (fd *FD) Read(fn func([]byte) (int, error), b []byte) (int, error) {
    58  	if err := fd.readLock(); err != nil {
    59  		return 0, err
    60  	}
    61  	defer fd.readUnlock()
    62  	if len(b) == 0 {
    63  		return 0, nil
    64  	}
    65  	fd.rmu.Lock()
    66  	if fd.rtimedout {
    67  		fd.rmu.Unlock()
    68  		return 0, ErrDeadlineExceeded
    69  	}
    70  	fd.raio = newAsyncIO(fn, b)
    71  	fd.rmu.Unlock()
    72  	n, err := fd.raio.Wait()
    73  	fd.raio = nil
    74  	if isHangup(err) {
    75  		err = io.EOF
    76  	}
    77  	if isInterrupted(err) {
    78  		err = ErrDeadlineExceeded
    79  	}
    80  	return n, err
    81  }
    82  
    83  // Write implements io.Writer.
    84  func (fd *FD) Write(fn func([]byte) (int, error), b []byte) (int, error) {
    85  	if err := fd.writeLock(); err != nil {
    86  		return 0, err
    87  	}
    88  	defer fd.writeUnlock()
    89  	fd.wmu.Lock()
    90  	if fd.wtimedout {
    91  		fd.wmu.Unlock()
    92  		return 0, ErrDeadlineExceeded
    93  	}
    94  	fd.waio = newAsyncIO(fn, b)
    95  	fd.wmu.Unlock()
    96  	n, err := fd.waio.Wait()
    97  	fd.waio = nil
    98  	if isInterrupted(err) {
    99  		err = ErrDeadlineExceeded
   100  	}
   101  	return n, err
   102  }
   103  
   104  // SetDeadline sets the read and write deadlines associated with fd.
   105  func (fd *FD) SetDeadline(t time.Time) error {
   106  	return setDeadlineImpl(fd, t, 'r'+'w')
   107  }
   108  
   109  // SetReadDeadline sets the read deadline associated with fd.
   110  func (fd *FD) SetReadDeadline(t time.Time) error {
   111  	return setDeadlineImpl(fd, t, 'r')
   112  }
   113  
   114  // SetWriteDeadline sets the write deadline associated with fd.
   115  func (fd *FD) SetWriteDeadline(t time.Time) error {
   116  	return setDeadlineImpl(fd, t, 'w')
   117  }
   118  
   119  func setDeadlineImpl(fd *FD, t time.Time, mode int) error {
   120  	d := t.Sub(time.Now())
   121  	if mode == 'r' || mode == 'r'+'w' {
   122  		fd.rmu.Lock()
   123  		defer fd.rmu.Unlock()
   124  		if fd.rtimer != nil {
   125  			fd.rtimer.Stop()
   126  			fd.rtimer = nil
   127  		}
   128  		fd.rtimedout = false
   129  	}
   130  	if mode == 'w' || mode == 'r'+'w' {
   131  		fd.wmu.Lock()
   132  		defer fd.wmu.Unlock()
   133  		if fd.wtimer != nil {
   134  			fd.wtimer.Stop()
   135  			fd.wtimer = nil
   136  		}
   137  		fd.wtimedout = false
   138  	}
   139  	if !t.IsZero() && d > 0 {
   140  		// Interrupt I/O operation once timer has expired
   141  		if mode == 'r' || mode == 'r'+'w' {
   142  			var timer *time.Timer
   143  			timer = time.AfterFunc(d, func() {
   144  				fd.rmu.Lock()
   145  				defer fd.rmu.Unlock()
   146  				if fd.rtimer != timer {
   147  					// deadline was changed
   148  					return
   149  				}
   150  				fd.rtimedout = true
   151  				if fd.raio != nil {
   152  					fd.raio.Cancel()
   153  				}
   154  			})
   155  			fd.rtimer = timer
   156  		}
   157  		if mode == 'w' || mode == 'r'+'w' {
   158  			var timer *time.Timer
   159  			timer = time.AfterFunc(d, func() {
   160  				fd.wmu.Lock()
   161  				defer fd.wmu.Unlock()
   162  				if fd.wtimer != timer {
   163  					// deadline was changed
   164  					return
   165  				}
   166  				fd.wtimedout = true
   167  				if fd.waio != nil {
   168  					fd.waio.Cancel()
   169  				}
   170  			})
   171  			fd.wtimer = timer
   172  		}
   173  	}
   174  	if !t.IsZero() && d <= 0 {
   175  		// Interrupt current I/O operation
   176  		if mode == 'r' || mode == 'r'+'w' {
   177  			fd.rtimedout = true
   178  			if fd.raio != nil {
   179  				fd.raio.Cancel()
   180  			}
   181  		}
   182  		if mode == 'w' || mode == 'r'+'w' {
   183  			fd.wtimedout = true
   184  			if fd.waio != nil {
   185  				fd.waio.Cancel()
   186  			}
   187  		}
   188  	}
   189  	return nil
   190  }
   191  
   192  // On Plan 9 only, expose the locking for the net code.
   193  
   194  // ReadLock wraps FD.readLock.
   195  func (fd *FD) ReadLock() error {
   196  	return fd.readLock()
   197  }
   198  
   199  // ReadUnlock wraps FD.readUnlock.
   200  func (fd *FD) ReadUnlock() {
   201  	fd.readUnlock()
   202  }
   203  
   204  func isHangup(err error) bool {
   205  	return err != nil && stringsHasSuffix(err.Error(), "Hangup")
   206  }
   207  
   208  func isInterrupted(err error) bool {
   209  	return err != nil && stringsHasSuffix(err.Error(), "interrupted")
   210  }
   211  
   212  // IsPollDescriptor reports whether fd is the descriptor being used by the poller.
   213  // This is only used for testing.
   214  func IsPollDescriptor(fd uintptr) bool {
   215  	return false
   216  }
   217  
   218  // RawControl invokes the user-defined function f for a non-IO
   219  // operation.
   220  func (fd *FD) RawControl(f func(uintptr)) error {
   221  	return errors.New("not implemented")
   222  }
   223  
   224  // RawRead invokes the user-defined function f for a read operation.
   225  func (fd *FD) RawRead(f func(uintptr) bool) error {
   226  	return errors.New("not implemented")
   227  }
   228  
   229  // RawWrite invokes the user-defined function f for a write operation.
   230  func (fd *FD) RawWrite(f func(uintptr) bool) error {
   231  	return errors.New("not implemented")
   232  }
   233
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