Add iov_clear()

Fill the spefified area with zeros.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

iov.c

@@ -62,6 +62,29 @@ size_t iov_to_buf(const struct iovec *iov, const unsigned int iov_cnt,
     return buf_off;
 }
 
+size_t iov_clear(const struct iovec *iov, const unsigned int iov_cnt,
+                 size_t iov_off, size_t size)
+{
+    size_t iovec_off, buf_off;
+    unsigned int i;
+
+    iovec_off = 0;
+    buf_off = 0;
+    for (i = 0; i < iov_cnt && size; i++) {
+        if (iov_off < (iovec_off + iov[i].iov_len)) {
+            size_t len = MIN((iovec_off + iov[i].iov_len) - iov_off , size);
+
+            memset(iov[i].iov_base + (iov_off - iovec_off), 0, len);
+
+            buf_off += len;
+            iov_off += len;
+            size -= len;
+        }
+        iovec_off += iov[i].iov_len;
+    }
+    return buf_off;
+}
+
 size_t iov_size(const struct iovec *iov, const unsigned int iov_cnt)
 {
     size_t len;

iov.h

@@ -17,5 +17,7 @@ size_t iov_from_buf(struct iovec *iov, unsigned int iov_cnt,
 size_t iov_to_buf(const struct iovec *iov, const unsigned int iov_cnt,
                   void *buf, size_t iov_off, size_t size);
 size_t iov_size(const struct iovec *iov, const unsigned int iov_cnt);
+size_t iov_clear(const struct iovec *iov, const unsigned int iov_cnt,
+                 size_t iov_off, size_t size);
 void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
                  FILE *fp, const char *prefix, size_t limit);