MINOR: buffers: add b_xfer() to transfer data between buffers
Instead of open-coding buffer-to-buffer transfers using blocks, let's
have a dedicated function for this. It also adjusts the buffer counts.
diff --git a/include/common/buf.h b/include/common/buf.h
index b93ef99..e72de91 100644
--- a/include/common/buf.h
+++ b/include/common/buf.h
@@ -514,6 +514,42 @@
return len;
}
+/* b_xfer() : transfers at most <count> bytes from buffer <src> to buffer <dst>
+ * and returns the number of bytes copied. The bytes are removed from <src> and
+ * added to <dst>. The caller is responsible for ensuring that <count> is not
+ * larger than b_room(dst).
+ */
+static inline size_t b_xfer(struct buffer *dst, struct buffer *src, size_t count)
+{
+ size_t ret, block1, block2;
+
+ ret = 0;
+ if (!count)
+ goto leave;
+
+ ret = b_data(src);
+ if (!ret)
+ goto leave;
+
+ if (ret > count)
+ ret = count;
+
+ block1 = b_contig_data(src, 0);
+ if (block1 > ret)
+ block1 = ret;
+ block2 = ret - block1;
+
+ if (block1)
+ __b_putblk(dst, b_head(src), block1);
+
+ if (block2)
+ __b_putblk(dst, b_peek(src, block1), block2);
+
+ b_del(src, ret);
+ leave:
+ return ret;
+}
+
/* b_rep_blk() : writes the block <blk> at position <pos> which must be in
* buffer <b>, and moves the part between <end> and the buffer's tail just
* after the end of the copy of <blk>. This effectively replaces the part