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Source file src/path/filepath/symlink.go

     1	// Copyright 2012 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	package filepath
     6	
     7	import (
     8		"bytes"
     9		"errors"
    10		"os"
    11	)
    12	
    13	const utf8RuneSelf = 0x80
    14	
    15	func walkSymlinks(path string) (string, error) {
    16		const maxIter = 255
    17		originalPath := path
    18		// consume path by taking each frontmost path element,
    19		// expanding it if it's a symlink, and appending it to b
    20		var b bytes.Buffer
    21		for n := 0; path != ""; n++ {
    22			if n > maxIter {
    23				return "", errors.New("EvalSymlinks: too many links in " + originalPath)
    24			}
    25	
    26			// find next path component, p
    27			var i = -1
    28			for j, c := range path {
    29				if c < utf8RuneSelf && os.IsPathSeparator(uint8(c)) {
    30					i = j
    31					break
    32				}
    33			}
    34			var p string
    35			if i == -1 {
    36				p, path = path, ""
    37			} else {
    38				p, path = path[:i], path[i+1:]
    39			}
    40	
    41			if p == "" {
    42				if b.Len() == 0 {
    43					// must be absolute path
    44					b.WriteRune(Separator)
    45				}
    46				continue
    47			}
    48	
    49			fi, err := os.Lstat(b.String() + p)
    50			if err != nil {
    51				return "", err
    52			}
    53			if fi.Mode()&os.ModeSymlink == 0 {
    54				b.WriteString(p)
    55				if path != "" || (b.Len() == 2 && len(p) == 2 && p[1] == ':') {
    56					b.WriteRune(Separator)
    57				}
    58				continue
    59			}
    60	
    61			// it's a symlink, put it at the front of path
    62			dest, err := os.Readlink(b.String() + p)
    63			if err != nil {
    64				return "", err
    65			}
    66			if IsAbs(dest) || os.IsPathSeparator(dest[0]) {
    67				b.Reset()
    68			}
    69			path = dest + string(Separator) + path
    70		}
    71		return Clean(b.String()), nil
    72	}
    73	

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