github.com/alash3al/go@v0.0.0-20150827002835-d497eeb00540/src/runtime/string1.go (about)

     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  package runtime
     6  
     7  import "unsafe"
     8  
     9  //go:nosplit
    10  func findnull(s *byte) int {
    11  	if s == nil {
    12  		return 0
    13  	}
    14  	p := (*[_MaxMem/2 - 1]byte)(unsafe.Pointer(s))
    15  	l := 0
    16  	for p[l] != 0 {
    17  		l++
    18  	}
    19  	return l
    20  }
    21  
    22  func findnullw(s *uint16) int {
    23  	if s == nil {
    24  		return 0
    25  	}
    26  	p := (*[_MaxMem/2/2 - 1]uint16)(unsafe.Pointer(s))
    27  	l := 0
    28  	for p[l] != 0 {
    29  		l++
    30  	}
    31  	return l
    32  }
    33  
    34  var maxstring uintptr = 256 // a hint for print
    35  
    36  //go:nosplit
    37  func gostringnocopy(str *byte) string {
    38  	ss := stringStruct{str: unsafe.Pointer(str), len: findnull(str)}
    39  	s := *(*string)(unsafe.Pointer(&ss))
    40  	for {
    41  		ms := maxstring
    42  		if uintptr(len(s)) <= ms || casuintptr(&maxstring, ms, uintptr(len(s))) {
    43  			break
    44  		}
    45  	}
    46  	return s
    47  }
    48  
    49  func gostringw(strw *uint16) string {
    50  	var buf [8]byte
    51  	str := (*[_MaxMem/2/2 - 1]uint16)(unsafe.Pointer(strw))
    52  	n1 := 0
    53  	for i := 0; str[i] != 0; i++ {
    54  		n1 += runetochar(buf[:], rune(str[i]))
    55  	}
    56  	s, b := rawstring(n1 + 4)
    57  	n2 := 0
    58  	for i := 0; str[i] != 0; i++ {
    59  		// check for race
    60  		if n2 >= n1 {
    61  			break
    62  		}
    63  		n2 += runetochar(b[n2:], rune(str[i]))
    64  	}
    65  	b[n2] = 0 // for luck
    66  	return s[:n2]
    67  }