libgo/go/syscall/dirent.go

   1 // Copyright 2009 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 // +build aix darwin dragonfly freebsd hurd js,wasm linux netbsd openbsd solaris
   6
   7 package syscall
   8
   9 import "unsafe"
  10
  11 // readInt returns the size-bytes unsigned integer in native byte order at offset off.
  12 func readInt(b []byte, off, size uintptr) (u uint64, ok bool) {
  13         if len(b) < int(off+size) {
  14                 return 0, false
  15         }
  16         if isBigEndian {
  17                 return readIntBE(b[off:], size), true
  18         }
  19         return readIntLE(b[off:], size), true
  20 }
  21
  22 func readIntBE(b []byte, size uintptr) uint64 {
  23         switch size {
  24         case 1:
  25                 return uint64(b[0])
  26         case 2:
  27                 _ = b[1] // bounds check hint to compiler; see golang.org/issue/14808
  28                 return uint64(b[1]) | uint64(b[0])<<8
  29         case 4:
  30                 _ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
  31                 return uint64(b[3]) | uint64(b[2])<<8 | uint64(b[1])<<16 | uint64(b[0])<<24
  32         case 8:
  33                 _ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
  34                 return uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
  35                         uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
  36         default:
  37                 panic("syscall: readInt with unsupported size")
  38         }
  39 }
  40
  41 func readIntLE(b []byte, size uintptr) uint64 {
  42         switch size {
  43         case 1:
  44                 return uint64(b[0])
  45         case 2:
  46                 _ = b[1] // bounds check hint to compiler; see golang.org/issue/14808
  47                 return uint64(b[0]) | uint64(b[1])<<8
  48         case 4:
  49                 _ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
  50                 return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24
  51         case 8:
  52                 _ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
  53                 return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
  54                         uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56
  55         default:
  56                 panic("syscall: readInt with unsupported size")
  57         }
  58 }
  59
  60 // ParseDirent parses up to max directory entries in buf,
  61 // appending the names to names. It returns the number of
  62 // bytes consumed from buf, the number of entries added
  63 // to names, and the new names slice.
  64 func ParseDirent(buf []byte, max int, names []string) (consumed int, count int, newnames []string) {
  65         origlen := len(buf)
  66         count = 0
  67         for max != 0 && len(buf) > 0 {
  68                 reclen, ok := direntReclen(buf)
  69                 if !ok || reclen > uint64(len(buf)) {
  70                         return origlen, count, names
  71                 }
  72                 rec := buf[:reclen]
  73                 buf = buf[reclen:]
  74                 ino, ok := direntIno(rec)
  75                 if !ok {
  76                         break
  77                 }
  78                 if ino == 0 { // File absent in directory.
  79                         continue
  80                 }
  81                 const namoff = uint64(unsafe.Offsetof(Dirent{}.Name))
  82                 namlen, ok := direntNamlen(rec)
  83                 if !ok || namoff+namlen > uint64(len(rec)) {
  84                         break
  85                 }
  86                 name := rec[namoff : namoff+namlen]
  87                 for i, c := range name {
  88                         if c == 0 {
  89                                 name = name[:i]
  90                                 break
  91                         }
  92                 }
  93                 // Check for useless names before allocating a string.
  94                 if string(name) == "." || string(name) == ".." {
  95                         continue
  96                 }
  97                 max--
  98                 count++
  99                 names = append(names, string(name))
 100         }
 101         return origlen - len(buf), count, names
 102 }