go dirent 源码
golang dirent 代码
文件路径：/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.
//go:build unix || (js && wasm)
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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