rand/rand.c: Rearrange some comparisons to avoid arithmetic overflow.

diff --git a/rand/rand.c b/rand/rand.c
index 90e8193..0d0650e 100644 (file)
--- a/rand/rand.c
+++ b/rand/rand.c
@@ -413,7 +413,7 @@ void rand_get(rand_pool *r, void *p, size_t sz)
   if (!sz)
     return;
   for (;;) {
-    if (r->o + sz <= RAND_BUFSZ) {
+    if (sz <= RAND_BUFSZ - r->o) {
       memcpy(o, r->buf + r->o, sz);
       r->o += sz;
       break;
@@ -475,7 +475,7 @@ void rand_getgood(rand_pool *r, void *p, size_t sz)
        chunk = r->obits / 8;
     }
 
-    if (chunk + r->o <= RAND_BUFSZ) {
+    if (chunk <= RAND_BUFSZ - r->o) {
       memcpy(o, r->buf + r->o, chunk);
       r->o += chunk;
     } else {