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// Copyright ©2015 The Go Authors
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// Copyright ©2015 Steve Francia <[email protected]>
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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//     http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package afero
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import (
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	"bytes"
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	"io"
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	"os"
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	"path/filepath"
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	"sort"
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	"strconv"
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	"strings"
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	"sync"
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	"time"
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)
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// byName implements sort.Interface.
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type byName []os.FileInfo
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func (f byName) Len() int           { return len(f) }
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func (f byName) Less(i, j int) bool { return f[i].Name() < f[j].Name() }
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func (f byName) Swap(i, j int)      { f[i], f[j] = f[j], f[i] }
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// ReadDir reads the directory named by dirname and returns
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// a list of sorted directory entries.
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func (a Afero) ReadDir(dirname string) ([]os.FileInfo, error) {
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	return ReadDir(a.Fs, dirname)
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}
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func ReadDir(fs Fs, dirname string) ([]os.FileInfo, error) {
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	f, err := fs.Open(dirname)
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	if err != nil {
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		return nil, err
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	}
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	list, err := f.Readdir(-1)
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	f.Close()
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	if err != nil {
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		return nil, err
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	}
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	sort.Sort(byName(list))
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	return list, nil
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}
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// ReadFile reads the file named by filename and returns the contents.
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// A successful call returns err == nil, not err == EOF. Because ReadFile
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// reads the whole file, it does not treat an EOF from Read as an error
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// to be reported.
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func (a Afero) ReadFile(filename string) ([]byte, error) {
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	return ReadFile(a.Fs, filename)
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}
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func ReadFile(fs Fs, filename string) ([]byte, error) {
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	f, err := fs.Open(filename)
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	if err != nil {
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		return nil, err
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	}
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	defer f.Close()
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	// It's a good but not certain bet that FileInfo will tell us exactly how much to
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	// read, so let's try it but be prepared for the answer to be wrong.
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	var n int64
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	if fi, err := f.Stat(); err == nil {
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		// Don't preallocate a huge buffer, just in case.
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		if size := fi.Size(); size < 1e9 {
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			n = size
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		}
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	}
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	// As initial capacity for readAll, use n + a little extra in case Size is zero,
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	// and to avoid another allocation after Read has filled the buffer.  The readAll
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	// call will read into its allocated internal buffer cheaply.  If the size was
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	// wrong, we'll either waste some space off the end or reallocate as needed, but
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	// in the overwhelmingly common case we'll get it just right.
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	return readAll(f, n+bytes.MinRead)
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}
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// readAll reads from r until an error or EOF and returns the data it read
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// from the internal buffer allocated with a specified capacity.
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func readAll(r io.Reader, capacity int64) (b []byte, err error) {
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	buf := bytes.NewBuffer(make([]byte, 0, capacity))
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	// If the buffer overflows, we will get bytes.ErrTooLarge.
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	// Return that as an error. Any other panic remains.
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	defer func() {
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		e := recover()
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		if e == nil {
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			return
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		}
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		if panicErr, ok := e.(error); ok && panicErr == bytes.ErrTooLarge {
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			err = panicErr
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		} else {
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			panic(e)
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		}
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	}()
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	_, err = buf.ReadFrom(r)
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	return buf.Bytes(), err
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}
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// ReadAll reads from r until an error or EOF and returns the data it read.
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// A successful call returns err == nil, not err == EOF. Because ReadAll is
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// defined to read from src until EOF, it does not treat an EOF from Read
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// as an error to be reported.
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func ReadAll(r io.Reader) ([]byte, error) {
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	return readAll(r, bytes.MinRead)
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}
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// WriteFile writes data to a file named by filename.
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// If the file does not exist, WriteFile creates it with permissions perm;
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// otherwise WriteFile truncates it before writing.
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func (a Afero) WriteFile(filename string, data []byte, perm os.FileMode) error {
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	return WriteFile(a.Fs, filename, data, perm)
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}
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func WriteFile(fs Fs, filename string, data []byte, perm os.FileMode) error {
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	f, err := fs.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, perm)
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	if err != nil {
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		return err
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	}
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	n, err := f.Write(data)
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	if err == nil && n < len(data) {
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		err = io.ErrShortWrite
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	}
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	if err1 := f.Close(); err == nil {
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		err = err1
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	}
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	return err
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}
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// Random number state.
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// We generate random temporary file names so that there's a good
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// chance the file doesn't exist yet - keeps the number of tries in
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// TempFile to a minimum.
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var (
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	randNum uint32
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	randmu  sync.Mutex
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)
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func reseed() uint32 {
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	return uint32(time.Now().UnixNano() + int64(os.Getpid()))
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}
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func nextRandom() string {
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	randmu.Lock()
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	r := randNum
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	if r == 0 {
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		r = reseed()
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	}
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	r = r*1664525 + 1013904223 // constants from Numerical Recipes
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	randNum = r
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	randmu.Unlock()
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	return strconv.Itoa(int(1e9 + r%1e9))[1:]
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}
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// TempFile creates a new temporary file in the directory dir,
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// opens the file for reading and writing, and returns the resulting *os.File.
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// The filename is generated by taking pattern and adding a random
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// string to the end. If pattern includes a "*", the random string
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// replaces the last "*".
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// If dir is the empty string, TempFile uses the default directory
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// for temporary files (see os.TempDir).
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// Multiple programs calling TempFile simultaneously
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// will not choose the same file. The caller can use f.Name()
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// to find the pathname of the file. It is the caller's responsibility
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// to remove the file when no longer needed.
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func (a Afero) TempFile(dir, pattern string) (f File, err error) {
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	return TempFile(a.Fs, dir, pattern)
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}
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func TempFile(fs Fs, dir, pattern string) (f File, err error) {
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	if dir == "" {
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		dir = os.TempDir()
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	}
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	var prefix, suffix string
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	if pos := strings.LastIndex(pattern, "*"); pos != -1 {
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		prefix, suffix = pattern[:pos], pattern[pos+1:]
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	} else {
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		prefix = pattern
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	}
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	nconflict := 0
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	for i := 0; i < 10000; i++ {
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		name := filepath.Join(dir, prefix+nextRandom()+suffix)
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		f, err = fs.OpenFile(name, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0o600)
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		if os.IsExist(err) {
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			if nconflict++; nconflict > 10 {
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				randmu.Lock()
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				randNum = reseed()
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				randmu.Unlock()
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			}
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			continue
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		}
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		break
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	}
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	return
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}
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// TempDir creates a new temporary directory in the directory dir
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// with a name beginning with prefix and returns the path of the
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// new directory.  If dir is the empty string, TempDir uses the
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// default directory for temporary files (see os.TempDir).
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// Multiple programs calling TempDir simultaneously
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// will not choose the same directory.  It is the caller's responsibility
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// to remove the directory when no longer needed.
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func (a Afero) TempDir(dir, prefix string) (name string, err error) {
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	return TempDir(a.Fs, dir, prefix)
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}
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func TempDir(fs Fs, dir, prefix string) (name string, err error) {
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	if dir == "" {
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		dir = os.TempDir()
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	}
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	nconflict := 0
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	for i := 0; i < 10000; i++ {
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		try := filepath.Join(dir, prefix+nextRandom())
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		err = fs.Mkdir(try, 0o700)
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		if os.IsExist(err) {
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			if nconflict++; nconflict > 10 {
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				randmu.Lock()
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				randNum = reseed()
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				randmu.Unlock()
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			}
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			continue
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		}
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		if err == nil {
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			name = try
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		}
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		break
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	}
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	return
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}
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