lib: random_fill() - Optimize away memmove()

We just need to track the position of how far the random_next buffer has
been used.

diff --git a/src/lib/randgen.c b/src/lib/randgen.c
index c56c01a718b3d0f26618f01fc233e87b56d70aac..f6b2da9c9902d0419783f76cb94584da3820541a 100644 (file)
--- a/src/lib/randgen.c
+++ b/src/lib/randgen.c
@@ -70,6 +70,7 @@ static int urandom_fd = -1;
    too large anyway so we don't unnecessarily waste CPU and memory. */
 #define RANDOM_READ_BUFFER_SIZE 32
 static unsigned char random_next[RANDOM_READ_BUFFER_SIZE];
+static size_t random_next_pos = 0;
 static size_t random_next_size = 0;
 
 static void random_open_urandom(void)
@@ -152,17 +153,19 @@ void random_fill(void *buf, size_t size)
                } else {
                        /* Asking for a little randomness. Read via a larger
                           buffer to reduce the number of syscalls. */
-                       if (random_next_size > 0)
-                               ret = random_next_size;
-                       else
+                       if (random_next_size > random_next_pos)
+                               ret = random_next_size - random_next_pos;
+                       else {
+                               random_next_pos = 0;
                                ret = random_read(random_next,
                                                  sizeof(random_next));
+                               random_next_size = ret < 0 ? 0 : ret;
+                       }
                        if (ret > 0) {
                                size_t used = I_MIN(size - pos, (size_t)ret);
-                               memcpy(PTR_OFFSET(buf, pos), random_next, used);
-                               random_next_size = ret - used;
-                               memmove(random_next, random_next + used,
-                                       random_next_size);
+                               memcpy(PTR_OFFSET(buf, pos),
+                                      random_next + random_next_pos, used);
+                               random_next_pos += used;
                                pos += used;
                        }
                }