1 files changed, 42 insertions, 0 deletions
diff --git a/src/libstddjb/fd_catn.c b/src/libstddjb/fd_catn.c
new file mode 100644
index 0000000..ca78546
--- /dev/null
+++ b/src/libstddjb/fd_catn.c
@@ -0,0 +1,42 @@
+/* ISC license. */
+
+#include <errno.h>
+#include <skalibs/allreadwrite.h>
+#include <skalibs/iobuffer.h>
+#include <skalibs/djbunix.h>
+
+unsigned int fd_catn (int from, int to, unsigned int n)
+{
+  unsigned int w = 0 ;
+  if (n >= IOBUFFER_SIZE)
+  {
+    iobuffer b ;
+    if (!iobuffer_init(&b, from, to)) return 0 ;
+    while (n >= IOBUFFER_SIZE)
+    {
+      register int r = iobuffer_fill(&b) ;
+      if (r <= 0)
+      {
+        iobuffer_finish(&b) ;
+        if (!r) errno = EPIPE ;
+        return w ;
+      }
+      if (!iobuffer_flush(&b))
+      {
+        iobuffer_finish(&b) ;
+        return w ;
+      }
+      n -= r ; w += r ;
+    }
+    iobuffer_finish(&b) ;
+  }
+
+  {
+    char buf[n] ;
+    unsigned int r = allread(from, buf, n) ;
+    unsigned int v = 0 ;
+    if (r) v = allwrite(to, buf, r) ;
+    w += v ;
+  }
+  return w ;
+}