usb-ks

USB Killswitch
git clone git://git.laack.co/usb-ks.git
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syscall_darwin.1_13.go (2759B)

      1 // Copyright 2019 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 darwin && go1.13
      6 // +build darwin,go1.13
      7 
      8 package unix
      9 
     10 import (
     11 	"unsafe"
     12 
     13 	"golang.org/x/sys/internal/unsafeheader"
     14 )
     15 
     16 //sys	closedir(dir uintptr) (err error)
     17 //sys	readdir_r(dir uintptr, entry *Dirent, result **Dirent) (res Errno)
     18 
     19 func fdopendir(fd int) (dir uintptr, err error) {
     20 	r0, _, e1 := syscall_syscallPtr(libc_fdopendir_trampoline_addr, uintptr(fd), 0, 0)
     21 	dir = uintptr(r0)
     22 	if e1 != 0 {
     23 		err = errnoErr(e1)
     24 	}
     25 	return
     26 }
     27 
     28 var libc_fdopendir_trampoline_addr uintptr
     29 
     30 //go:cgo_import_dynamic libc_fdopendir fdopendir "/usr/lib/libSystem.B.dylib"
     31 
     32 func Getdirentries(fd int, buf []byte, basep *uintptr) (n int, err error) {
     33 	// Simulate Getdirentries using fdopendir/readdir_r/closedir.
     34 	// We store the number of entries to skip in the seek
     35 	// offset of fd. See issue #31368.
     36 	// It's not the full required semantics, but should handle the case
     37 	// of calling Getdirentries or ReadDirent repeatedly.
     38 	// It won't handle assigning the results of lseek to *basep, or handle
     39 	// the directory being edited underfoot.
     40 	skip, err := Seek(fd, 0, 1 /* SEEK_CUR */)
     41 	if err != nil {
     42 		return 0, err
     43 	}
     44 
     45 	// We need to duplicate the incoming file descriptor
     46 	// because the caller expects to retain control of it, but
     47 	// fdopendir expects to take control of its argument.
     48 	// Just Dup'ing the file descriptor is not enough, as the
     49 	// result shares underlying state. Use Openat to make a really
     50 	// new file descriptor referring to the same directory.
     51 	fd2, err := Openat(fd, ".", O_RDONLY, 0)
     52 	if err != nil {
     53 		return 0, err
     54 	}
     55 	d, err := fdopendir(fd2)
     56 	if err != nil {
     57 		Close(fd2)
     58 		return 0, err
     59 	}
     60 	defer closedir(d)
     61 
     62 	var cnt int64
     63 	for {
     64 		var entry Dirent
     65 		var entryp *Dirent
     66 		e := readdir_r(d, &entry, &entryp)
     67 		if e != 0 {
     68 			return n, errnoErr(e)
     69 		}
     70 		if entryp == nil {
     71 			break
     72 		}
     73 		if skip > 0 {
     74 			skip--
     75 			cnt++
     76 			continue
     77 		}
     78 
     79 		reclen := int(entry.Reclen)
     80 		if reclen > len(buf) {
     81 			// Not enough room. Return for now.
     82 			// The counter will let us know where we should start up again.
     83 			// Note: this strategy for suspending in the middle and
     84 			// restarting is O(n^2) in the length of the directory. Oh well.
     85 			break
     86 		}
     87 
     88 		// Copy entry into return buffer.
     89 		var s []byte
     90 		hdr := (*unsafeheader.Slice)(unsafe.Pointer(&s))
     91 		hdr.Data = unsafe.Pointer(&entry)
     92 		hdr.Cap = reclen
     93 		hdr.Len = reclen
     94 		copy(buf, s)
     95 
     96 		buf = buf[reclen:]
     97 		n += reclen
     98 		cnt++
     99 	}
    100 	// Set the seek offset of the input fd to record
    101 	// how many files we've already returned.
    102 	_, err = Seek(fd, cnt, 0 /* SEEK_SET */)
    103 	if err != nil {
    104 		return n, err
    105 	}
    106 
    107 	return n, nil
    108 }