Allow evbuffer_read() to split across more than 2 iovecs

Previously it would only accept 2 iovecs at most, because our
previous_to_last nonsense didn't let it take any more.  This forced us
to do more reallocations in some cases when an extra small malloc
would have sufficed.

diff --git a/buffer.c b/buffer.c
index 700a1945bdb064936bd39bec9105e1708df7a65e..6f56dcb8f4d49602d3c64cb602dce79a50509274 100644 (file)
--- a/buffer.c
+++ b/buffer.c
@@ -1639,17 +1639,18 @@ _evbuffer_expand_fast(struct evbuffer *buf, size_t datlen, int n)
 #ifdef _EVENT_HAVE_SYS_UIO_H
 /* number of iovec we use for writev, fragmentation is going to determine
  * how much we end up writing */
-#define NUM_IOVEC 128
+#define NUM_WRITE_IOVEC 128
 #define IOV_TYPE struct iovec
 #define IOV_PTR_FIELD iov_base
 #define IOV_LEN_FIELD iov_len
 #else
-#define NUM_IOVEC 16
+#define NUM_WRITE_IOVEC 16
 #define IOV_TYPE WSABUF
 #define IOV_PTR_FIELD buf
 #define IOV_LEN_FIELD len
 #endif
 #endif
+#define NUM_READ_IOVEC 4
 
 #define EVBUFFER_MAX_READ      4096
 
@@ -1710,7 +1711,7 @@ evbuffer_read(struct evbuffer *buf, evutil_socket_t fd, int howmuch)
        int result;
 
 #ifdef USE_IOVEC_IMPL
-       int nvecs;
+       int nvecs, i, remaining;
 #else
        unsigned char *p;
 #endif
@@ -1753,28 +1754,24 @@ evbuffer_read(struct evbuffer *buf, evutil_socket_t fd, int howmuch)
 
 #ifdef USE_IOVEC_IMPL
        /* Since we can use iovecs, we're willing to use the last
-        * _two_ chains. */
-       if (_evbuffer_expand_fast(buf, howmuch, 2) == -1) {
+        * NUM_READ_IOVEC chains. */
+       if (_evbuffer_expand_fast(buf, howmuch, NUM_READ_IOVEC) == -1) {
                result = -1;
                goto done;
        } else {
-               IOV_TYPE vecs[2];
+               IOV_TYPE vecs[NUM_READ_IOVEC];
 #ifdef _EVBUFFER_IOVEC_IS_NATIVE
-               nvecs = _evbuffer_read_setup_vecs(buf, howmuch, vecs, 2,
-                   &chain, 1);
+               nvecs = _evbuffer_read_setup_vecs(buf, howmuch, vecs,
+                   NUM_READ_IOVEC, &chain, 1);
 #else
                /* We aren't using the native struct iovec.  Therefore,
                   we are on win32. */
-               struct evbuffer_iovec ev_vecs[2];
+               struct evbuffer_iovec ev_vecs[NUM_READ_IOVEC];
                nvecs = _evbuffer_read_setup_vecs(buf, howmuch, ev_vecs, 2,
                    &chain, 1);
 
-               if (nvecs == 2) {
-                       WSABUF_FROM_EVBUFFER_IOV(&vecs[1], &ev_vecs[1]);
-                       WSABUF_FROM_EVBUFFER_IOV(&vecs[0], &ev_vecs[0]);
-               } else if (nvecs == 1) {
-                       WSABUF_FROM_EVBUFFER_IOV(&vecs[0], &ev_vecs[0]);
-               }
+               for (i=0; i < n_vecs; ++i)
+                       WSABUF_FROM_EVBUFFER_IOV(&vecs[i], &ev_vecs[i]);
 #endif
 
 #ifdef WIN32
@@ -1827,19 +1824,18 @@ evbuffer_read(struct evbuffer *buf, evutil_socket_t fd, int howmuch)
        }
 
 #ifdef USE_IOVEC_IMPL
-       if (nvecs == 2) {
+       remaining = n;
+       for (i=0; i < nvecs; ++i) {
                ev_ssize_t space = CHAIN_SPACE_LEN(chain);
-               if (space < n) {
+               if (space < remaining) {
                        chain->off += space;
-                       chain->next->off += n-space;
-                       buf->last_with_data = chain->next;
+                       remaining -= space;
                } else {
-                       chain->off += n;
+                       chain->off += remaining;
                        buf->last_with_data = chain;
+                       break;
                }
-       } else {
-               chain->off += n;
-               buf->last_with_data = chain;
+               chain = chain->next;
        }
 #else
        chain->off += n;
@@ -1861,7 +1857,7 @@ static inline int
 evbuffer_write_iovec(struct evbuffer *buffer, evutil_socket_t fd,
     ev_ssize_t howmuch)
 {
-       IOV_TYPE iov[NUM_IOVEC];
+       IOV_TYPE iov[NUM_WRITE_IOVEC];
        struct evbuffer_chain *chain = buffer->first;
        int n, i = 0;
 
@@ -1872,7 +1868,7 @@ evbuffer_write_iovec(struct evbuffer *buffer, evutil_socket_t fd,
        /* XXX make this top out at some maximal data length?  if the
         * buffer has (say) 1MB in it, split over 128 chains, there's
         * no way it all gets written in one go. */
-       while (chain != NULL && i < NUM_IOVEC && howmuch) {
+       while (chain != NULL && i < NUM_WRITE_IOVEC && howmuch) {
 #ifdef USE_SENDFILE
                /* we cannot write the file info via writev */
                if (chain->flags & EVBUFFER_SENDFILE)