lib/scanner, vendor: Update github.com/chmduquesne/rollinghash (fixes #5334) (#5335)

Updates the package and fixes a test that depended on the old behavior
of Write() being equivalent to Reset()+Write() which is no longer the
case. The scanner already did resets after each block write, so this is
fine.

vendor/github.com/chmduquesne/rollinghash/roll/main.go

@@ -3,9 +3,11 @@ package main
 import (
 	"flag"
 	"fmt"
+	"hash"
 	"io"
 	"log"
 	"os"
+	"runtime/pprof"
 	"time"
 
 	"code.cloudfoundry.org/bytefmt"
@@ -33,7 +35,10 @@ func genMasks() (res []uint64) {
 	return
 }
 
-func hash2uint64(s []byte) (res uint64) {
+// Gets the hash sum as a uint64
+func sum64(h hash.Hash) (res uint64) {
+	buf := make([]byte, 0, 8)
+	s := h.Sum(buf)
 	for _, b := range s {
 		res <<= 8
 		res |= uint64(b)
@@ -42,18 +47,27 @@ func hash2uint64(s []byte) (res uint64) {
 }
 
 func main() {
+	cpuprofile := flag.String("cpuprofile", "", "write cpu profile to file")
 	dostats := flag.Bool("stats", false, "Do some stats about the rolling sum")
 	size := flag.String("size", "256M", "How much data to read")
 	flag.Parse()
 
+	if *cpuprofile != "" {
+		f, err := os.Create(*cpuprofile)
+		if err != nil {
+			log.Fatal(err)
+		}
+		pprof.StartCPUProfile(f)
+		defer pprof.StopCPUProfile()
+	}
+
 	fileSize, err := bytefmt.ToBytes(*size)
 	if err != nil {
 		log.Fatal(err)
 	}
 
 	bufsize := 16 * MiB
-	rbuf := make([]byte, bufsize)
-	hbuf := make([]byte, 0, 8)
+	buf := make([]byte, bufsize)
 	t := time.Now()
 
 	f, err := os.Open("/dev/urandom")
@@ -66,10 +80,10 @@ func main() {
 		}
 	}()
 
-	io.ReadFull(f, rbuf)
+	io.ReadFull(f, buf)
 
 	roll := rollsum.New()
-	roll.Write(rbuf[:64])
+	roll.Write(buf[:64])
 
 	masks := genMasks()
 	hits := make(map[uint64]uint64)
@@ -97,15 +111,15 @@ func main() {
 				fmt.Printf(status)
 				fmt.Printf("\r")
 			}
-			_, err := io.ReadFull(f, rbuf)
+			_, err := io.ReadFull(f, buf)
 			if err != nil {
 				panic(err)
 			}
 			k = 0
 		}
-		roll.Roll(rbuf[k])
+		roll.Roll(buf[k])
 		if *dostats {
-			s := hash2uint64(roll.Sum(hbuf))
+			s := sum64(roll)
 			for _, m := range masks {
 				if s&m == m {
 					hits[m] += 1