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package bytes
import (
crand "crypto/rand"
"github.com/savsgio/gotils/strconv"
"github.com/valyala/bytebufferpool"
)
var randBytesPool = bytebufferpool.Pool{}
// Rand returns dst with a cryptographically secure string random bytes.
//
// NOTE: Make sure that dst has the length you need.
func Rand(dst []byte) []byte {
buf := randBytesPool.Get()
buf.B = Extend(buf.B, len(dst))
if _, err := crand.Read(buf.B); err != nil {
panic(err)
}
size := len(dst)
for i, j := 0, 0; i < size; j++ {
// Mask bytes to get an index into the character slice.
if idx := int(buf.B[j%size] & charsetIdxMask); idx < len(charset) {
dst[i] = charset[idx]
i++
}
}
randBytesPool.Put(buf)
return dst
}
// Copy returns a copy of byte slice in a new pointer.
func Copy(b []byte) []byte {
return []byte(strconv.B2S(b))
}
// Equal reports whether a and b
// are the same length and contain the same bytes.
// A nil argument is equivalent to an empty slice.
func Equal(a, b []byte) bool {
return strconv.B2S(a) == strconv.B2S(b)
}
// Extend extends b to needLen bytes.
func Extend(b []byte, needLen int) []byte {
b = b[:cap(b)]
if n := needLen - cap(b); n > 0 {
b = append(b, make([]byte, n)...)
}
return b[:needLen]
}
// Prepend prepends bytes into a given byte slice.
func Prepend(dst []byte, src ...byte) []byte {
dstLen := len(dst)
srcLen := len(src)
dst = Extend(dst, dstLen+srcLen)
copy(dst[srcLen:], dst[:dstLen])
copy(dst[:srcLen], src)
return dst
}
// PrependString prepends a string into a given byte slice.
func PrependString(dst []byte, src string) []byte {
return Prepend(dst, strconv.S2B(src)...)
}
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