[master] b3043ce14 Optimize VRND_RandomCrypto()

[Nils Goroll]

commit b3043ce14065266fe2d94b233357cbe3e74eff3f
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Tue Jul 28 07:51:38 2020 +0200

    Optimize VRND_RandomCrypto()
    
    Try to read into the buffer in one go.
    
    closes #3366

diff --git a/lib/libvarnish/vrnd.c b/lib/libvarnish/vrnd.c
index 778c31fb2..891c40f27 100644
--- a/lib/libvarnish/vrnd.c
+++ b/lib/libvarnish/vrnd.c
@@ -168,17 +168,19 @@ int
 VRND_RandomCrypto(void *ptr, size_t len)
 {
 	int fd;
-	char *p;
+	char *p = ptr;
 	ssize_t l;
 
 	AN(ptr);
 	fd = open("/dev/urandom", O_RDONLY);
 	if (fd < 0)
 		return (-1);
-	for (p = ptr; len > 0; len--, p++) {
-		l = read(fd, p, 1);
-		if (l != 1)
+	while (len > 0) {
+		l = read(fd, p, len);
+		if (l < 0)
 			break;
+		p += l;
+		len -= l;
 	}
 	closefd(&fd);
 	return (len == 0 ? 0 : -1);