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  	"internal/stringslite"
    10  	"io"
    11  	"sync"
    12  	"syscall"
    13  	"time"
    14  )
    15  
    16  type FD struct {
    17  	// Lock sysfd and serialize access to Read and Write methods.
    18  	fdmu fdMutex
    19  
    20  	Destroy func()
    21  
    22  	// deadlines
    23  	rmu       sync.Mutex
    24  	wmu       sync.Mutex
    25  	raio      *asyncIO
    26  	waio      *asyncIO
    27  	rtimer    *time.Timer
    28  	wtimer    *time.Timer
    29  	rtimedout bool // set true when read deadline has been reached
    30  	wtimedout bool // set true when write deadline has been reached
    31  
    32  	// Whether this is a normal file.
    33  	// On Plan 9 we do not use this package for ordinary files,
    34  	// so this is always false, but the field is present because
    35  	// shared code in fd_mutex.go checks it.
    36  	isFile bool
    37  }
    38  
    39  // We need this to close out a file descriptor when it is unlocked,
    40  // but the real implementation has to live in the net package because
    41  // it uses os.File's.
    42  func (fd *FD) destroy() error {
    43  	if fd.Destroy != nil {
    44  		fd.Destroy()
    45  	}
    46  	return nil
    47  }
    48  
    49  // Close handles the locking for closing an FD. The real operation
    50  // is in the net package.
    51  func (fd *FD) Close() error {
    52  	if !fd.fdmu.increfAndClose() {
    53  		return errClosing(fd.isFile)
    54  	}
    55  	return nil
    56  }
    57  
    58  // Read implements io.Reader.
    59  func (fd *FD) Read(fn func([]byte) (int, error), b []byte) (int, error) {
    60  	if err := fd.readLock(); err != nil {
    61  		return 0, err
    62  	}
    63  	defer fd.readUnlock()
    64  	if len(b) == 0 {
    65  		return 0, nil
    66  	}
    67  	fd.rmu.Lock()
    68  	if fd.rtimedout {
    69  		fd.rmu.Unlock()
    70  		return 0, ErrDeadlineExceeded
    71  	}
    72  	fd.raio = newAsyncIO(fn, b)
    73  	fd.rmu.Unlock()
    74  	n, err := fd.raio.Wait()
    75  	fd.raio = nil
    76  	if isHangup(err) {
    77  		err = io.EOF
    78  	}
    79  	if isInterrupted(err) {
    80  		err = ErrDeadlineExceeded
    81  	}
    82  	return n, err
    83  }
    84  
    85  // Write implements io.Writer.
    86  func (fd *FD) Write(fn func([]byte) (int, error), b []byte) (int, error) {
    87  	if err := fd.writeLock(); err != nil {
    88  		return 0, err
    89  	}
    90  	defer fd.writeUnlock()
    91  	fd.wmu.Lock()
    92  	if fd.wtimedout {
    93  		fd.wmu.Unlock()
    94  		return 0, ErrDeadlineExceeded
    95  	}
    96  	fd.waio = newAsyncIO(fn, b)
    97  	fd.wmu.Unlock()
    98  	n, err := fd.waio.Wait()
    99  	fd.waio = nil
   100  	if isInterrupted(err) {
   101  		err = ErrDeadlineExceeded
   102  	}
   103  	return n, err
   104  }
   105  
   106  // SetDeadline sets the read and write deadlines associated with fd.
   107  func (fd *FD) SetDeadline(t time.Time) error {
   108  	return setDeadlineImpl(fd, t, 'r'+'w')
   109  }
   110  
   111  // SetReadDeadline sets the read deadline associated with fd.
   112  func (fd *FD) SetReadDeadline(t time.Time) error {
   113  	return setDeadlineImpl(fd, t, 'r')
   114  }
   115  
   116  // SetWriteDeadline sets the write deadline associated with fd.
   117  func (fd *FD) SetWriteDeadline(t time.Time) error {
   118  	return setDeadlineImpl(fd, t, 'w')
   119  }
   120  
   121  func setDeadlineImpl(fd *FD, t time.Time, mode int) error {
   122  	d := t.Sub(time.Now())
   123  	if mode == 'r' || mode == 'r'+'w' {
   124  		fd.rmu.Lock()
   125  		defer fd.rmu.Unlock()
   126  		if fd.rtimer != nil {
   127  			fd.rtimer.Stop()
   128  			fd.rtimer = nil
   129  		}
   130  		fd.rtimedout = false
   131  	}
   132  	if mode == 'w' || mode == 'r'+'w' {
   133  		fd.wmu.Lock()
   134  		defer fd.wmu.Unlock()
   135  		if fd.wtimer != nil {
   136  			fd.wtimer.Stop()
   137  			fd.wtimer = nil
   138  		}
   139  		fd.wtimedout = false
   140  	}
   141  	if !t.IsZero() && d > 0 {
   142  		// Interrupt I/O operation once timer has expired
   143  		if mode == 'r' || mode == 'r'+'w' {
   144  			var timer *time.Timer
   145  			timer = time.AfterFunc(d, func() {
   146  				fd.rmu.Lock()
   147  				defer fd.rmu.Unlock()
   148  				if fd.rtimer != timer {
   149  					// deadline was changed
   150  					return
   151  				}
   152  				fd.rtimedout = true
   153  				if fd.raio != nil {
   154  					fd.raio.Cancel()
   155  				}
   156  			})
   157  			fd.rtimer = timer
   158  		}
   159  		if mode == 'w' || mode == 'r'+'w' {
   160  			var timer *time.Timer
   161  			timer = time.AfterFunc(d, func() {
   162  				fd.wmu.Lock()
   163  				defer fd.wmu.Unlock()
   164  				if fd.wtimer != timer {
   165  					// deadline was changed
   166  					return
   167  				}
   168  				fd.wtimedout = true
   169  				if fd.waio != nil {
   170  					fd.waio.Cancel()
   171  				}
   172  			})
   173  			fd.wtimer = timer
   174  		}
   175  	}
   176  	if !t.IsZero() && d <= 0 {
   177  		// Interrupt current I/O operation
   178  		if mode == 'r' || mode == 'r'+'w' {
   179  			fd.rtimedout = true
   180  			if fd.raio != nil {
   181  				fd.raio.Cancel()
   182  			}
   183  		}
   184  		if mode == 'w' || mode == 'r'+'w' {
   185  			fd.wtimedout = true
   186  			if fd.waio != nil {
   187  				fd.waio.Cancel()
   188  			}
   189  		}
   190  	}
   191  	return nil
   192  }
   193  
   194  // On Plan 9 only, expose the locking for the net code.
   195  
   196  // ReadLock wraps FD.readLock.
   197  func (fd *FD) ReadLock() error {
   198  	return fd.readLock()
   199  }
   200  
   201  // ReadUnlock wraps FD.readUnlock.
   202  func (fd *FD) ReadUnlock() {
   203  	fd.readUnlock()
   204  }
   205  
   206  func isHangup(err error) bool {
   207  	return err != nil && stringslite.HasSuffix(err.Error(), "Hangup")
   208  }
   209  
   210  func isInterrupted(err error) bool {
   211  	return err != nil && stringslite.HasSuffix(err.Error(), "interrupted")
   212  }
   213  
   214  // IsPollDescriptor reports whether fd is the descriptor being used by the poller.
   215  // This is only used for testing.
   216  func IsPollDescriptor(fd uintptr) bool {
   217  	return false
   218  }
   219  
   220  // RawControl invokes the user-defined function f for a non-IO
   221  // operation.
   222  func (fd *FD) RawControl(f func(uintptr)) error {
   223  	return errors.New("not implemented")
   224  }
   225  
   226  // RawRead invokes the user-defined function f for a read operation.
   227  func (fd *FD) RawRead(f func(uintptr) bool) error {
   228  	return errors.New("not implemented")
   229  }
   230  
   231  // RawWrite invokes the user-defined function f for a write operation.
   232  func (fd *FD) RawWrite(f func(uintptr) bool) error {
   233  	return errors.New("not implemented")
   234  }
   235  
   236  func DupCloseOnExec(fd int) (int, string, error) {
   237  	nfd, err := syscall.Dup(int(fd), -1)
   238  	if err != nil {
   239  		return 0, "dup", err
   240  	}
   241  	// Plan9 has no syscall.CloseOnExec but
   242  	// its forkAndExecInChild closes all fds
   243  	// not related to the fork+exec.
   244  	return nfd, "", nil
   245  }
   246
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