Fix logic in correcting high values from FIONREAD

The old logic made sense back when buffer.c was an enormous linear
buffer, but it doesn't make any sense for the chain-based
implementation.

This patch also refactors the ioctl{socket}? call into its own function.

diff --git a/buffer.c b/buffer.c
index 6e0a838043bfa4b54099f0a6759fa72443209773..7b0262f3c1fdaf563d2e88bd4582216621bb2963 100644 (file)
--- a/buffer.c
+++ b/buffer.c
@@ -1856,13 +1856,31 @@ _evbuffer_read_setup_vecs(struct evbuffer *buf, ev_ssize_t howmuch,
        return i;
 }
 
+static int
+get_n_bytes_readable_on_socket(evutil_socket_t fd)
+{
+#if defined(FIONREAD) && defined(WIN32)
+       unsigned long lng = EVBUFFER_MAX_READ;
+       if (ioctlsocket(fd, FIONREAD, &lng) < 0)
+               return -1;
+       return (int)lng;
+#elif defined(FIONREAD)
+       int n = EVBUFFER_MAX_READ;
+       if (ioctl(fd, FIONREAD, &n) < 0)
+               return -1;
+       return n;
+#else
+       return EVBUFFER_MAX_READ;
+#endif
+}
+
 /* TODO(niels): should this function return ev_ssize_t and take ev_ssize_t
  * as howmuch? */
 int
 evbuffer_read(struct evbuffer *buf, evutil_socket_t fd, int howmuch)
 {
        struct evbuffer_chain *chain, **chainp;
-       int n = EVBUFFER_MAX_READ;
+       int n;
        int result;
 
 #ifdef USE_IOVEC_IMPL
@@ -1870,9 +1888,6 @@ evbuffer_read(struct evbuffer *buf, evutil_socket_t fd, int howmuch)
 #else
        unsigned char *p;
 #endif
-#if defined(FIONREAD) && defined(WIN32)
-       unsigned long lng = EVBUFFER_MAX_READ;
-#endif
 
        EVBUFFER_LOCK(buf);
 
@@ -1883,27 +1898,9 @@ evbuffer_read(struct evbuffer *buf, evutil_socket_t fd, int howmuch)
                goto done;
        }
 
-#if defined(FIONREAD)
-#ifdef WIN32
-       if (ioctlsocket(fd, FIONREAD, &lng) == -1 || (n=lng) <= 0) {
-#else
-       if (ioctl(fd, FIONREAD, &n) == -1 || n <= 0) {
-#endif
+       n = get_n_bytes_readable_on_socket(fd);
+       if (n <= 0 || n > EVBUFFER_MAX_READ)
                n = EVBUFFER_MAX_READ;
-       } else if (n > EVBUFFER_MAX_READ && n > howmuch) {
-               /*
-                * It's possible that a lot of data is available for
-                * reading.  We do not want to exhaust resources
-                * before the reader has a chance to do something
-                * about it.  If the reader does not tell us how much
-                * data we should read, we artificially limit it.
-                */
-               if (chain == NULL || n < EVBUFFER_MAX_READ)
-                       n = EVBUFFER_MAX_READ;
-               else if ((size_t)n > chain->buffer_len << 2)
-                       n = chain->buffer_len << 2;
-       }
-#endif
        if (howmuch < 0 || howmuch > n)
                howmuch = n;