syscall.go

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