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Source file src/syscall/dirent.go

  // Copyright 2009 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  // +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris
  
  package syscall
  
  import "unsafe"
  
  // readInt returns the size-bytes unsigned integer in native byte order at offset off.
  func readInt(b []byte, off, size uintptr) (u uint64, ok bool) {
  	if len(b) < int(off+size) {
  		return 0, false
  	}
  	if isBigEndian {
  		return readIntBE(b[off:], size), true
  	}
  	return readIntLE(b[off:], size), true
  }
  
  func readIntBE(b []byte, size uintptr) uint64 {
  	switch size {
  	case 1:
  		return uint64(b[0])
  	case 2:
  		_ = b[1] // bounds check hint to compiler; see golang.org/issue/14808
  		return uint64(b[1]) | uint64(b[0])<<8
  	case 4:
  		_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
  		return uint64(b[3]) | uint64(b[2])<<8 | uint64(b[1])<<16 | uint64(b[0])<<24
  	case 8:
  		_ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
  		return uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
  			uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
  	default:
  		panic("syscall: readInt with unsupported size")
  	}
  }
  
  func readIntLE(b []byte, size uintptr) uint64 {
  	switch size {
  	case 1:
  		return uint64(b[0])
  	case 2:
  		_ = b[1] // bounds check hint to compiler; see golang.org/issue/14808
  		return uint64(b[0]) | uint64(b[1])<<8
  	case 4:
  		_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
  		return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24
  	case 8:
  		_ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
  		return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
  			uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56
  	default:
  		panic("syscall: readInt with unsupported size")
  	}
  }
  
  // ParseDirent parses up to max directory entries in buf,
  // appending the names to names. It returns the number of
  // bytes consumed from buf, the number of entries added
  // to names, and the new names slice.
  func ParseDirent(buf []byte, max int, names []string) (consumed int, count int, newnames []string) {
  	origlen := len(buf)
  	count = 0
  	for max != 0 && len(buf) > 0 {
  		reclen, ok := direntReclen(buf)
  		if !ok || reclen > uint64(len(buf)) {
  			return origlen, count, names
  		}
  		rec := buf[:reclen]
  		buf = buf[reclen:]
  		ino, ok := direntIno(rec)
  		if !ok {
  			break
  		}
  		if ino == 0 { // File absent in directory.
  			continue
  		}
  		const namoff = uint64(unsafe.Offsetof(Dirent{}.Name))
  		namlen, ok := direntNamlen(rec)
  		if !ok || namoff+namlen > uint64(len(rec)) {
  			break
  		}
  		name := rec[namoff : namoff+namlen]
  		for i, c := range name {
  			if c == 0 {
  				name = name[:i]
  				break
  			}
  		}
  		// Check for useless names before allocating a string.
  		if string(name) == "." || string(name) == ".." {
  			continue
  		}
  		max--
  		count++
  		names = append(names, string(name))
  	}
  	return origlen - len(buf), count, names
  }
  

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