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|
package imagestore
import (
"crypto/rand"
"log"
)
type HashGenerator struct {
hashGetter chan string
length int
store ImageStore
}
func (this *HashGenerator) init() {
go func() {
storeObj := &StoreObject{
"",
"",
"original",
"",
}
for {
str := ""
for len(str) < this.length {
c := 10
bArr := make([]byte, c)
_, err := rand.Read(bArr)
if err != nil {
log.Println("error:", err)
break
}
for _, b := range bArr {
if len(str) == this.length {
break
}
/**
* Each byte will be in [0, 256), but we only care about:
*
* [48, 57] 0-9
* [65, 90] A-Z
* [97, 122] a-z
*
* Which means that the highest bit will always be zero, since the last byte with high bit
* zero is 01111111 = 127 which is higher than 122. Lower our odds of having to re-roll a byte by
* dividing by two (right bit shift of 1).
*/
b = b >> 1
// The byte is any of 0-9 A-Z a-z
byteIsAllowable := (b >= 48 && b <= 57) || (b >= 65 && b <= 90) || (b >= 97 && b <= 122)
if byteIsAllowable {
str += string(b)
}
}
}
storeObj.Name = str
exists, _ := this.store.Exists(storeObj)
if !exists {
this.hashGetter <- str
}
}
}()
}
func (this *HashGenerator) Get() string {
return <-this.hashGetter
}
|
