Convert scrypt C code to Go

ltcutil/scrypt/scrypt.go

@@ -1,16 +1,127 @@
 package scrypt
 
-// void scrypt_aux(unsigned char*);
-import "C"
-
 import (
 	"crypto/sha256"
+	"math/bits"
+	"unsafe"
 
 	"golang.org/x/crypto/pbkdf2"
 )
 
 func Scrypt(x []byte) []byte {
 	X := pbkdf2.Key(x, x, 1, 128, sha256.New)
-	C.scrypt_aux((*C.uchar)(&X[0]))
+	scrypt((*[32]uint32)(unsafe.Pointer(&X[0])))
 	return pbkdf2.Key(x, X, 1, 32, sha256.New)
 }
+
+func scrypt(X *[32]uint32) {
+	var (
+		V [1024][32]uint32
+		A = (*[16]uint32)(X[:16])
+		B = (*[16]uint32)(X[16:])
+	)
+
+	for i := 0; i < len(V); i++ {
+		V[i] = *X
+		salsa8(A, B)
+		salsa8(B, A)
+	}
+
+	for i := 0; i < len(V); i++ {
+		j := X[16] % uint32(len(V))
+		for k := 0; k < len(X); k++ {
+			X[k] ^= V[j][k]
+		}
+		salsa8(A, B)
+		salsa8(B, A)
+	}
+}
+
+func rotl(x uint32, k int) uint32 {
+	return uint32(bits.RotateLeft64(uint64(x), k))
+}
+
+func salsa8(A, B *[16]uint32) {
+	A[0] ^= B[0]
+	A[1] ^= B[1]
+	A[2] ^= B[2]
+	A[3] ^= B[3]
+	A[4] ^= B[4]
+	A[5] ^= B[5]
+	A[6] ^= B[6]
+	A[7] ^= B[7]
+	A[8] ^= B[8]
+	A[9] ^= B[9]
+	A[10] ^= B[10]
+	A[11] ^= B[11]
+	A[12] ^= B[12]
+	A[13] ^= B[13]
+	A[14] ^= B[14]
+	A[15] ^= B[15]
+
+	x00, x01, x02, x03 := A[0], A[1], A[2], A[3]
+	x04, x05, x06, x07 := A[4], A[5], A[6], A[7]
+	x08, x09, x10, x11 := A[8], A[9], A[10], A[11]
+	x12, x13, x14, x15 := A[12], A[13], A[14], A[15]
+
+	for i := 0; i < 4; i++ {
+		// Columns
+		x04 ^= rotl(x00+x12, 7)
+		x09 ^= rotl(x05+x01, 7)
+		x14 ^= rotl(x10+x06, 7)
+		x03 ^= rotl(x15+x11, 7)
+
+		x08 ^= rotl(x04+x00, 9)
+		x13 ^= rotl(x09+x05, 9)
+		x02 ^= rotl(x14+x10, 9)
+		x07 ^= rotl(x03+x15, 9)
+
+		x12 ^= rotl(x08+x04, 13)
+		x01 ^= rotl(x13+x09, 13)
+		x06 ^= rotl(x02+x14, 13)
+		x11 ^= rotl(x07+x03, 13)
+
+		x00 ^= rotl(x12+x08, 18)
+		x05 ^= rotl(x01+x13, 18)
+		x10 ^= rotl(x06+x02, 18)
+		x15 ^= rotl(x11+x07, 18)
+
+		// Rows
+		x01 ^= rotl(x00+x03, 7)
+		x06 ^= rotl(x05+x04, 7)
+		x11 ^= rotl(x10+x09, 7)
+		x12 ^= rotl(x15+x14, 7)
+
+		x02 ^= rotl(x01+x00, 9)
+		x07 ^= rotl(x06+x05, 9)
+		x08 ^= rotl(x11+x10, 9)
+		x13 ^= rotl(x12+x15, 9)
+
+		x03 ^= rotl(x02+x01, 13)
+		x04 ^= rotl(x07+x06, 13)
+		x09 ^= rotl(x08+x11, 13)
+		x14 ^= rotl(x13+x12, 13)
+
+		x00 ^= rotl(x03+x02, 18)
+		x05 ^= rotl(x04+x07, 18)
+		x10 ^= rotl(x09+x08, 18)
+		x15 ^= rotl(x14+x13, 18)
+	}
+
+	A[0] += x00
+	A[1] += x01
+	A[2] += x02
+	A[3] += x03
+	A[4] += x04
+	A[5] += x05
+	A[6] += x06
+	A[7] += x07
+	A[8] += x08
+	A[9] += x09
+	A[10] += x10
+	A[11] += x11
+	A[12] += x12
+	A[13] += x13
+	A[14] += x14
+	A[15] += x15
+}