address nick's comments and make evbuffer_pullup more efficient

svn:r680

diff --git a/buffer.c b/buffer.c
index 41d4bc2779cb4a24a70d2811c2b159292932b3e5..a3574ce712e1e4f3843580c98f8d58605a7ec2ef 100644 (file)
--- a/buffer.c
+++ b/buffer.c
@@ -339,28 +339,37 @@ evbuffer_pullup(struct evbuffer *buf, int size)
 
        if (size == -1)
                size = buf->total_len;
-       /* XXX Does it make more sense, if size > buf->total_len, to
-        * clip it downwards? */
+       /* if size > buf->total_len, we cannot guarantee to the user that she
+        * is going to have a long enough buffer afterwards; so we return
+        * NULL */
        if (size == 0 || size > buf->total_len)
                return (NULL);
 
-       /* No need to pull up anything; the first size bytes are already here. */
+       /* No need to pull up anything; the first size bytes are
+        * already here. */
        if (chain->off >= size)
                return chain->buffer + chain->misalign;
 
-       /* XXX is it possible that buf->chain will already have enough space
-        * to hold size bytes? */
-       if ((tmp = evbuffer_chain_new(size)) == NULL) {
-               event_warn("%s: out of memory\n", __func__);
-               return (NULL);
+       if (chain->buffer_len - chain->misalign >= size) {
+               /* already have enough space in the first chain */
+               size_t old_off = chain->off;
+               buffer = chain->buffer + chain->misalign + chain->off;
+               tmp = chain;
+               tmp->off = size;
+               size -= old_off;
+               chain = chain->next;
+       } else {
+               if ((tmp = evbuffer_chain_new(size)) == NULL) {
+                       event_warn("%s: out of memory\n", __func__);
+                       return (NULL);
+               }
+               buffer = tmp->buffer;
+               tmp->off = size;
+               buf->first = tmp;
        }
 
-       tmp->off = size;
-       buffer = tmp->buffer;
-
        /* Copy and free every chunk that will be entirely pulled into tmp */
-       for (chain = buf->first;
-           chain != NULL && size >= chain->off; chain = next) {
+       for (; chain != NULL && size >= chain->off; chain = next) {
                next = chain->next;
 
                memcpy(buffer, chain->buffer + chain->misalign, chain->off);
@@ -378,10 +387,9 @@ evbuffer_pullup(struct evbuffer *buf, int size)
                buf->last = tmp;
        }
 
-       buf->first = tmp;
        tmp->next = chain;
 
-       return (tmp->buffer);
+       return (tmp->buffer + tmp->misalign);
 }
 
 /*