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82 lines
1.5 KiB
82 lines
1.5 KiB
package utils
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import (
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"encoding/hex"
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"math/big"
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)
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// use to look up number of 1 bit in 4 bits
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var halfByteLookup = [16]int{0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4}
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// FromHex returns the bytes represented by the hexadecimal string s.
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// s may be prefixed with "0x".
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func FromHex(s string) []byte {
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if len(s) > 1 {
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if s[0:2] == "0x" || s[0:2] == "0X" {
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s = s[2:]
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}
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}
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if len(s)%2 == 1 {
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s = "0" + s
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}
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return Hex2Bytes(s)
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}
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// Hex2Bytes returns the bytes represented by the hexadecimal string str.
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func Hex2Bytes(str string) []byte {
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h, _ := hex.DecodeString(str)
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return h
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}
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// counts number of one bits in a byte
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func countOneBitsInByte(by byte) int {
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return halfByteLookup[by&0x0F] + halfByteLookup[by>>4]
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}
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// CountOneBits counts the number of 1 bit in byte array
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func CountOneBits(arr []byte) int64 {
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if arr == nil {
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return 0
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}
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if len(arr) == 0 {
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return 0
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}
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count := 0
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for i := range arr {
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count += countOneBitsInByte(arr[i])
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}
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return int64(count)
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}
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func BytesMiddle(a, b []byte) []byte {
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if a == nil && b == nil {
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return []byte{128}
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}
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if len(a) > len(b) {
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tmp := make([]byte, len(a))
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if b == nil {
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for i, _ := range tmp {
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tmp[i] = 255
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}
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}
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copy(tmp, b)
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b = tmp
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} else if len(a) < len(b) {
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tmp := make([]byte, len(b))
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if a == nil {
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for i, _ := range tmp {
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tmp[i] = 0
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}
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}
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copy(tmp, a)
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a = tmp
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}
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aI := big.NewInt(0).SetBytes(a)
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bI := big.NewInt(0).SetBytes(b)
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aI.Add(aI, bI)
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aI.Div(aI, big.NewInt(2))
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return aI.Bytes()
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}
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