--- a/src/fs.c	Mon Dec 17 16:55:22 2018 +0900
+++ b/src/fs.c	Thu Jan 17 19:11:19 2019 +0900
@@ -453,6 +453,37 @@
     st->size = ip->size;
 }
 
+__code cbc_readi (struct inode *ip, char *dst, uint off, uint n, __code (*next)(int ret))
+{
+    uint tot, m;
+    struct buf *bp;
+
+    if (ip->type == T_DEV) {
+        if (ip->major < 0 || ip->major >= NDEV || !devsw[ip->major].read) {
+            goto next(-1);
+        }
+
+        goto cbc_devsw[ip->major].read(ip, dst, n);
+    }
+
+    if (off > ip->size || off + n < off) {
+        goto next(-1);
+    }
+
+    if (off + n > ip->size) {
+        n = ip->size - off;
+    }
+
+    for (tot = 0; tot < n; tot += m, off += m, dst += m) {
+        bp = bread(ip->dev, bmap(ip, off / BSIZE));
+        m = min(n - tot, BSIZE - off%BSIZE);
+        memmove(dst, bp->data + off % BSIZE, m);
+        brelse(bp);
+    }
+
+    goto next(n);
+}
+
 //PAGEBREAK!
 // Read data from inode.
 int readi (struct inode *ip, char *dst, uint off, uint n)