syscall.go (3093B)
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 //go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris || zos 6 // +build aix darwin dragonfly freebsd linux netbsd openbsd solaris zos 7 8 // Package unix contains an interface to the low-level operating system 9 // primitives. OS details vary depending on the underlying system, and 10 // by default, godoc will display OS-specific documentation for the current 11 // system. If you want godoc to display OS documentation for another 12 // system, set $GOOS and $GOARCH to the desired system. For example, if 13 // you want to view documentation for freebsd/arm on linux/amd64, set $GOOS 14 // to freebsd and $GOARCH to arm. 15 // 16 // The primary use of this package is inside other packages that provide a more 17 // portable interface to the system, such as "os", "time" and "net". Use 18 // those packages rather than this one if you can. 19 // 20 // For details of the functions and data types in this package consult 21 // the manuals for the appropriate operating system. 22 // 23 // These calls return err == nil to indicate success; otherwise 24 // err represents an operating system error describing the failure and 25 // holds a value of type syscall.Errno. 26 package unix // import "golang.org/x/sys/unix" 27 28 import ( 29 "bytes" 30 "strings" 31 "unsafe" 32 33 "golang.org/x/sys/internal/unsafeheader" 34 ) 35 36 // ByteSliceFromString returns a NUL-terminated slice of bytes 37 // containing the text of s. If s contains a NUL byte at any 38 // location, it returns (nil, EINVAL). 39 func ByteSliceFromString(s string) ([]byte, error) { 40 if strings.IndexByte(s, 0) != -1 { 41 return nil, EINVAL 42 } 43 a := make([]byte, len(s)+1) 44 copy(a, s) 45 return a, nil 46 } 47 48 // BytePtrFromString returns a pointer to a NUL-terminated array of 49 // bytes containing the text of s. If s contains a NUL byte at any 50 // location, it returns (nil, EINVAL). 51 func BytePtrFromString(s string) (*byte, error) { 52 a, err := ByteSliceFromString(s) 53 if err != nil { 54 return nil, err 55 } 56 return &a[0], nil 57 } 58 59 // ByteSliceToString returns a string form of the text represented by the slice s, with a terminating NUL and any 60 // bytes after the NUL removed. 61 func ByteSliceToString(s []byte) string { 62 if i := bytes.IndexByte(s, 0); i != -1 { 63 s = s[:i] 64 } 65 return string(s) 66 } 67 68 // BytePtrToString takes a pointer to a sequence of text and returns the corresponding string. 69 // If the pointer is nil, it returns the empty string. It assumes that the text sequence is terminated 70 // at a zero byte; if the zero byte is not present, the program may crash. 71 func BytePtrToString(p *byte) string { 72 if p == nil { 73 return "" 74 } 75 if *p == 0 { 76 return "" 77 } 78 79 // Find NUL terminator. 80 n := 0 81 for ptr := unsafe.Pointer(p); *(*byte)(ptr) != 0; n++ { 82 ptr = unsafe.Pointer(uintptr(ptr) + 1) 83 } 84 85 var s []byte 86 h := (*unsafeheader.Slice)(unsafe.Pointer(&s)) 87 h.Data = unsafe.Pointer(p) 88 h.Len = n 89 h.Cap = n 90 91 return string(s) 92 } 93 94 // Single-word zero for use when we need a valid pointer to 0 bytes. 95 var _zero uintptr