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1 // Copyright 2009 The Go Authors. All rights reserved.
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2 // Use of this source code is governed by a BSD-style
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3 // license that can be found in the LICENSE file.
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4
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5 //go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris || zos
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6 // +build aix darwin dragonfly freebsd linux netbsd openbsd solaris zos
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7
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8 // Package unix contains an interface to the low-level operating system
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9 // primitives. OS details vary depending on the underlying system, and
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10 // by default, godoc will display OS-specific documentation for the current
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11 // system. If you want godoc to display OS documentation for another
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12 // system, set $GOOS and $GOARCH to the desired system. For example, if
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13 // you want to view documentation for freebsd/arm on linux/amd64, set $GOOS
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14 // to freebsd and $GOARCH to arm.
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15 //
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16 // The primary use of this package is inside other packages that provide a more
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17 // portable interface to the system, such as "os", "time" and "net". Use
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18 // those packages rather than this one if you can.
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19 //
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20 // For details of the functions and data types in this package consult
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21 // the manuals for the appropriate operating system.
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22 //
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23 // These calls return err == nil to indicate success; otherwise
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24 // err represents an operating system error describing the failure and
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25 // holds a value of type syscall.Errno.
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26 package unix // import "golang.org/x/sys/unix"
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27
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28 import (
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29 "bytes"
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30 "strings"
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31 "unsafe"
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32
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33 "golang.org/x/sys/internal/unsafeheader"
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34 )
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35
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36 // ByteSliceFromString returns a NUL-terminated slice of bytes
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37 // containing the text of s. If s contains a NUL byte at any
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38 // location, it returns (nil, EINVAL).
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39 func ByteSliceFromString(s string) ([]byte, error) {
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40 if strings.IndexByte(s, 0) != -1 {
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41 return nil, EINVAL
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42 }
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43 a := make([]byte, len(s)+1)
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44 copy(a, s)
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45 return a, nil
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46 }
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47
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48 // BytePtrFromString returns a pointer to a NUL-terminated array of
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49 // bytes containing the text of s. If s contains a NUL byte at any
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50 // location, it returns (nil, EINVAL).
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51 func BytePtrFromString(s string) (*byte, error) {
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52 a, err := ByteSliceFromString(s)
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53 if err != nil {
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54 return nil, err
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55 }
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56 return &a[0], nil
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57 }
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58
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59 // ByteSliceToString returns a string form of the text represented by the slice s, with a terminating NUL and any
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60 // bytes after the NUL removed.
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61 func ByteSliceToString(s []byte) string {
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62 if i := bytes.IndexByte(s, 0); i != -1 {
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63 s = s[:i]
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64 }
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65 return string(s)
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66 }
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67
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68 // BytePtrToString takes a pointer to a sequence of text and returns the corresponding string.
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69 // If the pointer is nil, it returns the empty string. It assumes that the text sequence is terminated
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70 // at a zero byte; if the zero byte is not present, the program may crash.
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71 func BytePtrToString(p *byte) string {
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72 if p == nil {
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73 return ""
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74 }
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75 if *p == 0 {
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76 return ""
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77 }
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78
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79 // Find NUL terminator.
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80 n := 0
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81 for ptr := unsafe.Pointer(p); *(*byte)(ptr) != 0; n++ {
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82 ptr = unsafe.Pointer(uintptr(ptr) + 1)
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83 }
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84
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85 var s []byte
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86 h := (*unsafeheader.Slice)(unsafe.Pointer(&s))
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87 h.Data = unsafe.Pointer(p)
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88 h.Len = n
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89 h.Cap = n
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90
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91 return string(s)
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92 }
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93
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94 // Single-word zero for use when we need a valid pointer to 0 bytes.
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95 var _zero uintptr
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