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Allow evbuffer_read() to split across more than 2 iovecs

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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.
This commit is contained in:
Nick Mathewson 2010-03-10 23:39:30 -05:00
parent 6f47bd12ed
commit e470ad3c35
1 changed files with 21 additions and 25 deletions
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46
buffer.c
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@ -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)