github.com/megatontech/mynoteforgo@v0.0.0-20200507084910-5d0c6ea6e890/源码/os/dir_unix.go (about) 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,!arm,!arm64 dragonfly freebsd js,wasm linux nacl netbsd openbsd solaris 6 7 package os 8 9 import ( 10 "io" 11 "runtime" 12 "syscall" 13 ) 14 15 // Auxiliary information if the File describes a directory 16 type dirInfo struct { 17 buf []byte // buffer for directory I/O 18 nbuf int // length of buf; return value from Getdirentries 19 bufp int // location of next record in buf. 20 } 21 22 const ( 23 // More than 5760 to work around https://golang.org/issue/24015. 24 blockSize = 8192 25 ) 26 27 func (d *dirInfo) close() {} 28 29 func (f *File) readdirnames(n int) (names []string, err error) { 30 // If this file has no dirinfo, create one. 31 if f.dirinfo == nil { 32 f.dirinfo = new(dirInfo) 33 // The buffer must be at least a block long. 34 f.dirinfo.buf = make([]byte, blockSize) 35 } 36 d := f.dirinfo 37 38 size := n 39 if size <= 0 { 40 size = 100 41 n = -1 42 } 43 44 names = make([]string, 0, size) // Empty with room to grow. 45 for n != 0 { 46 // Refill the buffer if necessary 47 if d.bufp >= d.nbuf { 48 d.bufp = 0 49 var errno error 50 d.nbuf, errno = f.pfd.ReadDirent(d.buf) 51 runtime.KeepAlive(f) 52 if errno != nil { 53 return names, wrapSyscallError("readdirent", errno) 54 } 55 if d.nbuf <= 0 { 56 break // EOF 57 } 58 } 59 60 // Drain the buffer 61 var nb, nc int 62 nb, nc, names = syscall.ParseDirent(d.buf[d.bufp:d.nbuf], n, names) 63 d.bufp += nb 64 n -= nc 65 } 66 if n >= 0 && len(names) == 0 { 67 return names, io.EOF 68 } 69 return names, nil 70 }