Bugfix: cpu: Correct results found by scrypt algorithm

- Fix scanhash_scrypt prototype in driver-cpu.c
- Always iterate over nonces in big-endian (since scrypt implementation works with big endian ints, this is faster)
- Always swap big-endian nonce to little-endian for "data" storage (expected format); thanks to Dmitry Eremin-Solenikov for reporting this issue

driver-cpu.c

@@ -130,9 +130,7 @@ extern bool scanhash_sse2_32(struct thr_info*, const unsigned char *pmidstate, u
 	uint32_t max_nonce, uint32_t *last_nonce,
 	uint32_t nonce);
 
-extern bool scanhash_scrypt(struct thr_info *thr, int thr_id, unsigned char *pdata, unsigned char *scratchbuf,
-	const unsigned char *ptarget,
-	uint32_t max_nonce, unsigned long *hashes_done);
+extern bool scanhash_scrypt(struct thr_info *, const unsigned char *pmidstate, unsigned char *pdata, unsigned char *phash1, unsigned char __maybe_unused *phash, const unsigned char *ptarget, uint32_t max_nonce, uint32_t *last_nonce, uint32_t nonce);
 
 
 

scrypt.c

@@ -465,27 +465,33 @@ bool scanhash_scrypt(struct thr_info *thr, const unsigned char __maybe_unused *p
 		return ret;
 	}
 
+	// we always hash in big endian
+	n = htobe32(n);
+	
 	while(1) {
 		uint32_t ostate[8];
 
-		*nonce = ++n;
-		data[19] = htobe32(n);
+		data[19] = n;
 		scrypt_1024_1_1_256_sp(data, scratchbuf, ostate);
 		tmp_hash7 = be32toh(ostate[7]);
 
 		if (unlikely(tmp_hash7 <= Htarg)) {
-			((uint32_t *)pdata)[19] = htobe32(n);
-			*last_nonce = n;
+			// nonce passed in data is always little-endian, while we are always hashing in big endian
+			*nonce = swab32(n);
 			ret = true;
 			break;
 		}
 
 		if (unlikely((n >= max_nonce) || thr->work_restart)) {
-			*last_nonce = n;
 			break;
 		}
+		
+		++n;
 	}
 
-	free(scratchbuf);;
+	// last_nonce is expected to be host-endian
+	*last_nonce = be32toh(n);
+	
+	free(scratchbuf);
 	return ret;
 }