return 0, err
	}
	if fd.IsStream && len(p) > maxRW {
		p = p[:maxRW]
	}
	for {
		n, err := ignoringEINTRIO(syscall.Read, fd.Sysfd, p)
		if err != nil {
			n = 0
			if err == syscall.EAGAIN && fd.pd.pollable() {
				if err = fd.pd.waitRead(fd.isFile); err == nil {
					continue
				}
			}
		}
		err = fd.eofError(n, err)
		return n, err
	}
}

#include <sys/rtprio.h>
#include <sys/signal.h>
#include <sys/unistd.h>
#include <errno.h>
#include <signal.h>
*/
import "C"

const (
	EINTR     = C.EINTR
	EFAULT    = C.EFAULT
	EBUSY     = C.EBUSY
	EAGAIN    = C.EAGAIN
	ETIMEDOUT = C.ETIMEDOUT

	O_WRONLY   = C.O_WRONLY
	O_NONBLOCK = C.O_NONBLOCK
	O_CREAT    = C.O_CREAT
	O_TRUNC    = C.O_TRUNC
	O_CLOEXEC  = C.O_CLOEXEC

	PROT_NONE  = C.PROT_NONE

			n = int(remain)
		}
		pos1 := pos
		n, err = syscall.Sendfile(dst, src, &pos1, n)
		if err == syscall.EAGAIN || err == syscall.EINTR {
			// partial write may have occurred
			n = int(pos1 - pos)
		}
		if n > 0 {
			pos += int64(n)
			written += int64(n)
			remain -= int64(n)
			continue
		} else if err != syscall.EAGAIN && err != syscall.EINTR {
			// This includes syscall.ENOSYS (no kernel

#include <sys/event.h>
#include <sys/time.h>
#include <sys/ucontext.h>
#include <sys/unistd.h>
#include <errno.h>
#include <signal.h>
*/
import "C"

const (
	EINTR  = C.EINTR
	EFAULT = C.EFAULT
	EAGAIN = C.EAGAIN

	O_WRONLY   = C.O_WRONLY
	O_NONBLOCK = C.O_NONBLOCK
	O_CREAT    = C.O_CREAT
	O_TRUNC    = C.O_TRUNC
	O_CLOEXEC  = C.O_CLOEXEC

	PROT_NONE  = C.PROT_NONE
	PROT_READ  = C.PROT_READ

	_CPU_LEVEL_WHICH = C.CPU_LEVEL_WHICH // Actual mask/id for which.
	_CPU_WHICH_PID   = C.CPU_WHICH_PID   // Specifies a process id.
)

const (
	EINTR     = C.EINTR
	EFAULT    = C.EFAULT
	EAGAIN    = C.EAGAIN
	ETIMEDOUT = C.ETIMEDOUT

	O_WRONLY   = C.O_WRONLY
	O_NONBLOCK = C.O_NONBLOCK
	O_CREAT    = C.O_CREAT
	O_TRUNC    = C.O_TRUNC
	O_CLOEXEC  = C.O_CLOEXEC

	PROT_NONE  = C.PROT_NONE

#include <errno.h>
#include <signal.h>
#include <sys/event.h>
#include <sys/mman.h>
#include <pthread.h>
#include <fcntl.h>
*/
import "C"

const (
	EINTR     = C.EINTR
	EFAULT    = C.EFAULT
	EAGAIN    = C.EAGAIN
	ETIMEDOUT = C.ETIMEDOUT

	PROT_NONE  = C.PROT_NONE
	PROT_READ  = C.PROT_READ
	PROT_WRITE = C.PROT_WRITE
	PROT_EXEC  = C.PROT_EXEC

	MAP_ANON    = C.MAP_ANON
	MAP_PRIVATE = C.MAP_PRIVATE

		// don't implement sendfile), and other errors.
		// We should end the loop when there is no error
		// returned from sendfile(2) or it is not a retryable error.
		if err != syscall.EAGAIN {
			break
		}
		if err = dstFD.pd.waitWrite(dstFD.isFile); err != nil {
			break
		}
	}
	handled = written != 0 || (err != syscall.ENOSYS && err != syscall.EINVAL)
	return

		if int64(n) > remain {
			n = int(remain)
		}
		n, err = syscall.Sendfile(dst, src, nil, n)
		if n > 0 {
			written += int64(n)
			remain -= int64(n)
			continue
		} else if err != syscall.EAGAIN && err != syscall.EINTR {
			// This includes syscall.ENOSYS (no kernel
			// support) and syscall.EINVAL (fd types which
			// don't implement sendfile), and other errors.
			// We should end the loop when there is no error

			// will wake up a goroutine waiting to write;
			// that goroutine will try the write again,
			// and the appropriate thing will happen based
			// on what that write returns (success, EPIPE, EAGAIN).
			if ev.flags&_EV_EOF != 0 {
				mode += 'w'
			}
		case _EVFILT_WRITE:
			mode += 'w'
		}
		if mode != 0 {
			var pd *pollDesc
			var tag uintptr
			if goarch.PtrSize == 4 {

	if err := fd.incref(); err != nil {
		return 0, err
	}
	defer fd.decref()
	for {
		n, err := syscall.ReadDir(fd.Sysfd, buf, cookie)
		if err != nil {
			n = 0
			if err == syscall.EAGAIN && fd.pd.pollable() {
				if err = fd.pd.waitRead(fd.isFile); err == nil {
					continue
				}
			}
		}
		// Do not call eofError; caller does not expect to see io.EOF.
		return n, err
	}
}