diff -r dc514a5d42a5 -r 765cf785b7fa src/utils.c
--- a/src/utils.c	Mon Apr 03 19:20:30 2023 +0200
+++ b/src/utils.c	Mon Apr 03 19:48:00 2023 +0200
@@ -84,27 +84,9 @@
         cx_write_func wfnc,
         size_t n
 ) {
-    if (n == 0) {
-        return 0;
-    }
-
-    const size_t bufsize = CX_STREAM_COPY_BUF_SIZE;
-    char lbuf[bufsize];
-    size_t ncp = 0;
-
-    size_t r;
-    size_t rn = bufsize > n ? n : bufsize;
-    while ((r = rfnc(lbuf, 1, rn, src)) != 0) {
-        r = wfnc(lbuf, 1, r, dest);
-        ncp += r;
-        n -= r;
-        rn = bufsize > n ? n : bufsize;
-        if (r == 0 || n == 0) {
-            break;
-        }
-    }
-
-    return ncp;
+    char buf[CX_STREAM_COPY_BUF_SIZE];
+    return cx_stream_bncopy(src, dest, rfnc, wfnc,
+                            buf, CX_STREAM_COPY_BUF_SIZE, n);
 }
 
 #ifndef CX_SZMUL_BUILTIN