diff --git a/src/libbio/bwrite.c b/src/libbio/bwrite.c
new file mode 100644
index 0000000..2dfeaaa
--- /dev/null
+++ b/src/libbio/bwrite.c
@@ -0,0 +1,38 @@
+#include	"lib9.h"
+#include	<bio.h>
+
+long
+Bwrite(Biobuf *bp, void *ap, long count)
+{
+	long c;
+	unsigned char *p;
+	int i, n, oc;
+
+	p = ap;
+	c = count;
+	oc = bp->ocount;
+
+	while(c > 0) {
+		n = -oc;
+		if(n > c)
+			n = c;
+		if(n == 0) {
+			if(bp->state != Bwactive)
+				return Beof;
+			i = write(bp->fid, bp->bbuf, bp->bsize);
+			if(i != bp->bsize) {
+				bp->state = Binactive;
+				return Beof;
+			}
+			bp->offset += i;
+			oc = -bp->bsize;
+			continue;
+		}
+		memmove(bp->ebuf+oc, p, n);
+		oc += n;
+		c -= n;
+		p += n;
+	}
+	bp->ocount = oc;
+	return count-c;
+}