@@ -3,74 +3,56 @@ package gonanoid
33import (
44 "crypto/rand"
55 "errors"
6- "fmt"
76 "math"
87)
98
9+ // defaultAlphabet is the alphabet used for ID characters by default.
1010var defaultAlphabet = []rune ("_-0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ" )
11+
1112const (
12- defaultSize = 21
13- defaultMaskSize = 5
13+ defaultSize = 21
1414)
1515
16- // Generator function
17- type Generator func ([]byte ) (int , error )
18-
19- // BytesGenerator is the default bytes generator
20- var BytesGenerator Generator = rand .Read
21-
22- func initMasks (params ... int ) []uint {
23- var size int
24- if len (params ) == 0 {
25- size = defaultMaskSize
26- } else {
27- size = params [0 ]
28- }
29- masks := make ([]uint , size )
30- for i := 0 ; i < size ; i ++ {
31- shift := 3 + i
32- masks [i ] = (2 << uint (shift )) - 1
33- }
34- return masks
35- }
36-
37- func getMask (alphabet []rune , masks []uint ) int {
38- for i := 0 ; i < len (masks ); i ++ {
39- curr := int (masks [i ])
40- if curr >= len (alphabet )- 1 {
41- return curr
16+ // getMask generates bit mask used to obtain bits from the random bytes that are used to get index of random character
17+ // from the alphabet. Example: if the alphabet has 6 = (110)_2 characters it is sufficient to use mask 7 = (111)_2
18+ func getMask (alphabetSize int ) int {
19+ for i := 1 ; i <= 8 ; i ++ {
20+ mask := (2 << uint (i )) - 1
21+ if mask >= alphabetSize - 1 {
22+ return mask
4223 }
4324 }
4425 return 0
4526}
4627
4728// Generate is a low-level function to change alphabet and ID size.
48- func Generate (rawAlphabet string , size int ) (string , error ) {
49- alphabet := []rune (rawAlphabet )
29+ func Generate (alphabet string , size int ) (string , error ) {
30+ chars := []rune (alphabet )
5031
5132 if len (alphabet ) == 0 || len (alphabet ) > 255 {
52- return "" , fmt . Errorf ("alphabet must not empty and contain no more than 255 chars. Current len is %d" , len ( alphabet ) )
33+ return "" , errors . New ("alphabet must not be empty and contain no more than 255 chars" )
5334 }
5435 if size <= 0 {
55- return "" , fmt . Errorf ("size must be positive integer" )
36+ return "" , errors . New ("size must be positive integer" )
5637 }
5738
58- masks := initMasks (size )
59- mask := getMask (alphabet , masks )
39+ mask := getMask (len (chars ))
40+ // estimate how many random bytes we will need for the ID, we might actually need more but this is tradeoff
41+ // between average case and worst case
6042 ceilArg := 1.6 * float64 (mask * size ) / float64 (len (alphabet ))
6143 step := int (math .Ceil (ceilArg ))
6244
6345 id := make ([]rune , size )
6446 bytes := make ([]byte , step )
6547 for j := 0 ; ; {
66- _ , err := BytesGenerator (bytes )
48+ _ , err := rand . Read (bytes )
6749 if err != nil {
6850 return "" , err
6951 }
7052 for i := 0 ; i < step ; i ++ {
7153 currByte := bytes [i ] & byte (mask )
72- if currByte < byte (len (alphabet )) {
73- id [j ] = alphabet [currByte ]
54+ if currByte < byte (len (chars )) {
55+ id [j ] = chars [currByte ]
7456 j ++
7557 if j == size {
7658 return string (id [:size ]), nil
@@ -80,22 +62,32 @@ func Generate(rawAlphabet string, size int) (string, error) {
8062 }
8163}
8264
83- // Nanoid generates secure URL-friendly unique ID.
84- func Nanoid (param ... int ) (string , error ) {
65+ // MustGenerate is the same as Generate but panics on error.
66+ func MustGenerate (alphabet string , size int ) string {
67+ id , err := Generate (alphabet , size )
68+ if err != nil {
69+ panic (err )
70+ }
71+ return id
72+ }
73+
74+ // New generates secure URL-friendly unique ID.
75+ // Accepts optional parameter - length of the ID to be generated (21 by default).
76+ func New (l ... int ) (string , error ) {
8577 var size int
8678 switch {
87- case len (param ) == 0 :
79+ case len (l ) == 0 :
8880 size = defaultSize
89- case len (param ) == 1 :
90- size = param [0 ]
81+ case len (l ) == 1 :
82+ size = l [0 ]
9183 if size < 0 {
9284 return "" , errors .New ("negative id length" )
9385 }
9486 default :
9587 return "" , errors .New ("unexpected parameter" )
9688 }
9789 bytes := make ([]byte , size )
98- _ , err := BytesGenerator (bytes )
90+ _ , err := rand . Read (bytes )
9991 if err != nil {
10092 return "" , err
10193 }
@@ -106,24 +98,9 @@ func Nanoid(param ...int) (string, error) {
10698 return string (id [:size ]), nil
10799}
108100
109- // ID provides more golang idiomatic interface for generating IDs.
110- // Calling ID is shorter yet still clear `gonanoid.ID(20)` and it requires the lengths parameter by default.
111- func ID (l int ) (string , error ) {
112- return Nanoid (l )
113- }
114-
115- // MustID is the same as ID but panics on error.
116- func MustID (l int ) string {
117- id , err := Nanoid (l )
118- if err != nil {
119- panic (err )
120- }
121- return id
122- }
123-
124- // MustGenerate is the same as Generate but panics on error.
125- func MustGenerate (rawAlphabet string , size int ) string {
126- id , err := Generate (rawAlphabet , size )
101+ // Must is the same as New but panics on error.
102+ func Must (l ... int ) string {
103+ id , err := New (l ... )
127104 if err != nil {
128105 panic (err )
129106 }
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