fd_unixjs.go

     1  // Copyright 2023 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  //go:build unix || (js && wasm)
     6  
     7  package poll
     8  
     9  import "syscall"
    10  
    11  type SysFile struct {
    12  	// Writev cache.
    13  	iovecs *[]syscall.Iovec
    14  }
    15  
    16  func (s *SysFile) init() {}
    17  
    18  func (s *SysFile) destroy(fd int) error {
    19  	// We don't use ignoringEINTR here because POSIX does not define
    20  	// whether the descriptor is closed if close returns EINTR.
    21  	// If the descriptor is indeed closed, using a loop would race
    22  	// with some other goroutine opening a new descriptor.
    23  	// (The Linux kernel guarantees that it is closed on an EINTR error.)
    24  	return CloseFunc(fd)
    25  }
    26  
    27  // dupCloseOnExecOld is the traditional way to dup an fd and
    28  // set its O_CLOEXEC bit, using two system calls.
    29  func dupCloseOnExecOld(fd int) (int, string, error) {
    30  	syscall.ForkLock.RLock()
    31  	defer syscall.ForkLock.RUnlock()
    32  	newfd, err := syscall.Dup(fd)
    33  	if err != nil {
    34  		return -1, "dup", err
    35  	}
    36  	syscall.CloseOnExec(newfd)
    37  	return newfd, "", nil
    38  }
    39  
    40  // Fchdir wraps syscall.Fchdir.
    41  func (fd *FD) Fchdir() error {
    42  	if err := fd.incref(); err != nil {
    43  		return err
    44  	}
    45  	defer fd.decref()
    46  	return syscall.Fchdir(fd.Sysfd)
    47  }
    48  
    49  // ReadDirent wraps syscall.ReadDirent.
    50  // We treat this like an ordinary system call rather than a call
    51  // that tries to fill the buffer.
    52  func (fd *FD) ReadDirent(buf []byte) (int, error) {
    53  	if err := fd.incref(); err != nil {
    54  		return 0, err
    55  	}
    56  	defer fd.decref()
    57  	for {
    58  		n, err := ignoringEINTRIO(syscall.ReadDirent, fd.Sysfd, buf)
    59  		if err != nil {
    60  			n = 0
    61  			if err == syscall.EAGAIN && fd.pd.pollable() {
    62  				if err = fd.pd.waitRead(fd.isFile); err == nil {
    63  					continue
    64  				}
    65  			}
    66  		}
    67  		// Do not call eofError; caller does not expect to see io.EOF.
    68  		return n, err
    69  	}
    70  }
    71  
    72  // Seek wraps syscall.Seek.
    73  func (fd *FD) Seek(offset int64, whence int) (int64, error) {
    74  	if err := fd.incref(); err != nil {
    75  		return 0, err
    76  	}
    77  	defer fd.decref()
    78  	return syscall.Seek(fd.Sysfd, offset, whence)
    79  }
    80
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