/usr/share/gocode/src/golang.org/x/crypto/cryptobyte/string.go is in golang-golang-x-crypto-dev 1:0.0~git20170629.0.5ef0053-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 | // Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package cryptobyte implements building and parsing of byte strings for
// DER-encoded ASN.1 and TLS messages. See the examples for the Builder and
// String types to get started.
package cryptobyte // import "golang.org/x/crypto/cryptobyte"
// String represents a string of bytes. It provides methods for parsing
// fixed-length and length-prefixed values from it.
type String []byte
// read advances a String by n bytes and returns them. If less than n bytes
// remain, it returns nil.
func (s *String) read(n int) []byte {
if len(*s) < n {
return nil
}
v := (*s)[:n]
*s = (*s)[n:]
return v
}
// Skip advances the String by n byte and reports whether it was successful.
func (s *String) Skip(n int) bool {
return s.read(n) != nil
}
// ReadUint8 decodes an 8-bit value into out and advances over it. It
// returns true on success and false on error.
func (s *String) ReadUint8(out *uint8) bool {
v := s.read(1)
if v == nil {
return false
}
*out = uint8(v[0])
return true
}
// ReadUint16 decodes a big-endian, 16-bit value into out and advances over it.
// It returns true on success and false on error.
func (s *String) ReadUint16(out *uint16) bool {
v := s.read(2)
if v == nil {
return false
}
*out = uint16(v[0])<<8 | uint16(v[1])
return true
}
// ReadUint24 decodes a big-endian, 24-bit value into out and advances over it.
// It returns true on success and false on error.
func (s *String) ReadUint24(out *uint32) bool {
v := s.read(3)
if v == nil {
return false
}
*out = uint32(v[0])<<16 | uint32(v[1])<<8 | uint32(v[2])
return true
}
// ReadUint32 decodes a big-endian, 32-bit value into out and advances over it.
// It returns true on success and false on error.
func (s *String) ReadUint32(out *uint32) bool {
v := s.read(4)
if v == nil {
return false
}
*out = uint32(v[0])<<24 | uint32(v[1])<<16 | uint32(v[2])<<8 | uint32(v[3])
return true
}
func (s *String) readUnsigned(out *uint32, length int) bool {
v := s.read(length)
if v == nil {
return false
}
var result uint32
for i := 0; i < length; i++ {
result <<= 8
result |= uint32(v[i])
}
*out = result
return true
}
func (s *String) readLengthPrefixed(lenLen int, outChild *String) bool {
lenBytes := s.read(lenLen)
if lenBytes == nil {
return false
}
var length uint32
for _, b := range lenBytes {
length = length << 8
length = length | uint32(b)
}
if int(length) < 0 {
// This currently cannot overflow because we read uint24 at most, but check
// anyway in case that changes in the future.
return false
}
v := s.read(int(length))
if v == nil {
return false
}
*outChild = v
return true
}
// ReadUint8LengthPrefixed reads the content of an 8-bit length-prefixed value
// into out and advances over it. It returns true on success and false on
// error.
func (s *String) ReadUint8LengthPrefixed(out *String) bool {
return s.readLengthPrefixed(1, out)
}
// ReadUint16LengthPrefixed reads the content of a big-endian, 16-bit
// length-prefixed value into out and advances over it. It returns true on
// success and false on error.
func (s *String) ReadUint16LengthPrefixed(out *String) bool {
return s.readLengthPrefixed(2, out)
}
// ReadUint24LengthPrefixed reads the content of a big-endian, 24-bit
// length-prefixed value into out and advances over it. It returns true on
// success and false on error.
func (s *String) ReadUint24LengthPrefixed(out *String) bool {
return s.readLengthPrefixed(3, out)
}
// ReadBytes reads n bytes into out and advances over them. It returns true on
// success and false and error.
func (s *String) ReadBytes(out *[]byte, n int) bool {
v := s.read(n)
if v == nil {
return false
}
*out = v
return true
}
// CopyBytes copies len(out) bytes into out and advances over them. It returns
// true on success and false on error.
func (s *String) CopyBytes(out []byte) bool {
n := len(out)
v := s.read(n)
if v == nil {
return false
}
return copy(out, v) == n
}
// Empty reports whether the string does not contain any bytes.
func (s String) Empty() bool {
return len(s) == 0
}
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