github.com/v2fly/tools@v0.100.0/internal/fastwalk/fastwalk_dirent_namlen_linux.go (about)

     1  // Copyright 2018 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 linux && !appengine
     6  // +build linux,!appengine
     7  
     8  package fastwalk
     9  
    10  import (
    11  	"bytes"
    12  	"syscall"
    13  	"unsafe"
    14  )
    15  
    16  func direntNamlen(dirent *syscall.Dirent) uint64 {
    17  	const fixedHdr = uint16(unsafe.Offsetof(syscall.Dirent{}.Name))
    18  	nameBuf := (*[unsafe.Sizeof(dirent.Name)]byte)(unsafe.Pointer(&dirent.Name[0]))
    19  	const nameBufLen = uint16(len(nameBuf))
    20  	limit := dirent.Reclen - fixedHdr
    21  	if limit > nameBufLen {
    22  		limit = nameBufLen
    23  	}
    24  	nameLen := bytes.IndexByte(nameBuf[:limit], 0)
    25  	if nameLen < 0 {
    26  		panic("failed to find terminating 0 byte in dirent")
    27  	}
    28  	return uint64(nameLen)
    29  }