MINOR: ring: rename totlen vs msglen in ring_write()

The ring_write() function uses confusing variable names: totlen is in
fact the length of the message, not the total length that is going to
be written. Let's rename it msglen and have a real "needed" that
corresponds to the total size we're going to write. We also add a
BUG_ON_HOT() to catch mistakes causing discrepancies.

diff --git a/src/ring.c b/src/ring.c
index 95e1e991f7fca8268e942656c3f6ad570df973c8..37f2474d4ac1a7193608b18e6871d64c8ba3c3b9 100644 (file)
--- a/src/ring.c
+++ b/src/ring.c
@@ -175,8 +175,9 @@ ssize_t ring_write(struct ring *ring, size_t maxlen, const struct ist pfx[], siz
 {
        struct buffer *buf = &ring->buf;
        struct appctx *appctx;
-       size_t totlen = 0;
+       size_t msglen = 0;
        size_t lenlen;
+       size_t needed;
        uint64_t dellen;
        int dellenlen;
        ssize_t sent = 0;
@@ -191,20 +192,27 @@ ssize_t ring_write(struct ring *ring, size_t maxlen, const struct ist pfx[], siz
         * copying due to the varint encoding of the length.
         */
        for (i = 0; i < npfx; i++)
-               totlen += pfx[i].len;
+               msglen += pfx[i].len;
        for (i = 0; i < nmsg; i++)
-               totlen += msg[i].len;
+               msglen += msg[i].len;
 
-       if (totlen > maxlen)
-               totlen = maxlen;
+       if (msglen > maxlen)
+               msglen = maxlen;
 
-       lenlen = varint_bytes(totlen);
+       lenlen = varint_bytes(msglen);
+
+       /* We need:
+        *   - lenlen bytes for the size encoding
+        *   - msglen for the message
+        *   - one byte for the new marker
+        */
+       needed = lenlen + msglen + 1;
 
        HA_RWLOCK_WRLOCK(RING_LOCK, &ring->lock);
-       if (lenlen + totlen + 1 + 1 > b_size(buf))
+       if (needed + 1 > b_size(buf))
                goto done_buf;
 
-       while (b_room(buf) < lenlen + totlen + 1) {
+       while (b_room(buf) < needed) {
                /* we need to delete the oldest message (from the end),
                 * and we have to stop if there's a reader stuck there.
                 * Unless there's corruption in the buffer it's guaranteed
@@ -223,31 +231,32 @@ ssize_t ring_write(struct ring *ring, size_t maxlen, const struct ist pfx[], siz
        }
 
        /* OK now we do have room */
-       __b_put_varint(buf, totlen);
+       __b_put_varint(buf, msglen);
 
-       totlen = 0;
+       msglen = 0;
        for (i = 0; i < npfx; i++) {
                size_t len = pfx[i].len;
 
-               if (len + totlen > maxlen)
-                       len = maxlen - totlen;
+               if (len + msglen > maxlen)
+                       len = maxlen - msglen;
                if (len)
                        __b_putblk(buf, pfx[i].ptr, len);
-               totlen += len;
+               msglen += len;
        }
 
        for (i = 0; i < nmsg; i++) {
                size_t len = msg[i].len;
 
-               if (len + totlen > maxlen)
-                       len = maxlen - totlen;
+               if (len + msglen > maxlen)
+                       len = maxlen - msglen;
                if (len)
                        __b_putblk(buf, msg[i].ptr, len);
-               totlen += len;
+               msglen += len;
        }
 
        *b_tail(buf) = 0; buf->data++; // new read counter
-       sent = lenlen + totlen + 1;
+       sent = lenlen + msglen + 1;
+       BUG_ON_HOT(sent != needed);
 
        /* notify potential readers */
        list_for_each_entry(appctx, &ring->waiters, wait_entry)