The Tor Browser: ipc/chromium/src/third_party/libevent/buffer.c@6474c204b198 (annotated)

ipc/chromium/src/third_party/libevent/buffer.c@6474c204b198 (annotated)

ipc/chromium/src/third_party/libevent/buffer.c

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /*
  * Copyright (c) 2002-2007 Niels Provos <provos@citi.umich.edu>
  * Copyright (c) 2007-2012 Niels Provos and Nick Mathewson
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  * 3. The name of the author may not be used to endorse or promote products
  *    derived from this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 #include "event2/event-config.h"
 #ifdef WIN32
 #include <winsock2.h>
 #include <windows.h>
 #include <io.h>
 #endif
 #ifdef _EVENT_HAVE_VASPRINTF
 /* If we have vasprintf, we need to define this before we include stdio.h. */
 #define _GNU_SOURCE
 #endif
 #include <sys/types.h>
 #ifdef _EVENT_HAVE_SYS_TIME_H
 #include <sys/time.h>
 #endif
 #ifdef _EVENT_HAVE_SYS_SOCKET_H
 #include <sys/socket.h>
 #endif
 #ifdef _EVENT_HAVE_SYS_UIO_H
 #include <sys/uio.h>
 #endif
 #ifdef _EVENT_HAVE_SYS_IOCTL_H
 #include <sys/ioctl.h>
 #endif
 #ifdef _EVENT_HAVE_SYS_MMAN_H
 #include <sys/mman.h>
 #endif
 #ifdef _EVENT_HAVE_SYS_SENDFILE_H
 #include <sys/sendfile.h>
 #endif
 #include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #ifdef _EVENT_HAVE_STDARG_H
 #include <stdarg.h>
 #endif
 #ifdef _EVENT_HAVE_UNISTD_H
 #include <unistd.h>
 #endif
 #include <limits.h>
 #include "event2/event.h"
 #include "event2/buffer.h"
 #include "event2/buffer_compat.h"
 #include "event2/bufferevent.h"
 #include "event2/bufferevent_compat.h"
 #include "event2/bufferevent_struct.h"
 #include "event2/thread.h"
 #include "event2/event-config.h"
 #include "log-internal.h"
 #include "mm-internal.h"
 #include "util-internal.h"
 #include "evthread-internal.h"
 #include "evbuffer-internal.h"
 #include "bufferevent-internal.h"
 /* some systems do not have MAP_FAILED */
 #ifndef MAP_FAILED
 #define MAP_FAILED	((void *)-1)
 #endif
 /* send file support */
 #if defined(_EVENT_HAVE_SYS_SENDFILE_H) && defined(_EVENT_HAVE_SENDFILE) && defined(__linux__)
 #define USE_SENDFILE		1
 #define SENDFILE_IS_LINUX	1
 #elif defined(_EVENT_HAVE_SENDFILE) && defined(__FreeBSD__)
 #define USE_SENDFILE		1
 #define SENDFILE_IS_FREEBSD	1
 #elif defined(_EVENT_HAVE_SENDFILE) && defined(__APPLE__)
 #define USE_SENDFILE		1
 #define SENDFILE_IS_MACOSX	1
 #elif defined(_EVENT_HAVE_SENDFILE) && defined(__sun__) && defined(__svr4__)
 #define USE_SENDFILE		1
 #define SENDFILE_IS_SOLARIS	1
 #endif
 #ifdef USE_SENDFILE
 static int use_sendfile = 1;
 #endif
 #ifdef _EVENT_HAVE_MMAP
 static int use_mmap = 1;
 #endif
 /* Mask of user-selectable callback flags. */
 #define EVBUFFER_CB_USER_FLAGS	    0xffff
 /* Mask of all internal-use-only flags. */
 #define EVBUFFER_CB_INTERNAL_FLAGS  0xffff0000
 /* Flag set if the callback is using the cb_obsolete function pointer  */
 #define EVBUFFER_CB_OBSOLETE	       0x00040000
 /* evbuffer_chain support */
 #define CHAIN_SPACE_PTR(ch) ((ch)->buffer + (ch)->misalign + (ch)->off)
 #define CHAIN_SPACE_LEN(ch) ((ch)->flags & EVBUFFER_IMMUTABLE ? \
 : (ch)->buffer_len - ((ch)->misalign + (ch)->off))
 #define CHAIN_PINNED(ch)  (((ch)->flags & EVBUFFER_MEM_PINNED_ANY) != 0)
 #define CHAIN_PINNED_R(ch)  (((ch)->flags & EVBUFFER_MEM_PINNED_R) != 0)
 static void evbuffer_chain_align(struct evbuffer_chain *chain);
 static int evbuffer_chain_should_realign(struct evbuffer_chain *chain,
     size_t datalen);
 static void evbuffer_deferred_callback(struct deferred_cb *cb, void *arg);
 static int evbuffer_ptr_memcmp(const struct evbuffer *buf,
     const struct evbuffer_ptr *pos, const char *mem, size_t len);
 static struct evbuffer_chain *evbuffer_expand_singlechain(struct evbuffer *buf,
     size_t datlen);
 #ifdef WIN32
 static int evbuffer_readfile(struct evbuffer *buf, evutil_socket_t fd,
     ev_ssize_t howmuch);
 #else
 #define evbuffer_readfile evbuffer_read
 #endif
 static struct evbuffer_chain *
 evbuffer_chain_new(size_t size)
 {
 	struct evbuffer_chain *chain;
 	size_t to_alloc;
 	size += EVBUFFER_CHAIN_SIZE;
 	/* get the next largest memory that can hold the buffer */
 	to_alloc = MIN_BUFFER_SIZE;
 	while (to_alloc < size)
 		to_alloc <<= 1;
 	/* we get everything in one chunk */
 	if ((chain = mm_malloc(to_alloc)) == NULL)
 		return (NULL);
 	memset(chain, 0, EVBUFFER_CHAIN_SIZE);
 	chain->buffer_len = to_alloc - EVBUFFER_CHAIN_SIZE;
 	/* this way we can manipulate the buffer to different addresses,
 	 * which is required for mmap for example.
 	 */
 	chain->buffer = EVBUFFER_CHAIN_EXTRA(u_char, chain);
 	return (chain);
 }
 static inline void
 evbuffer_chain_free(struct evbuffer_chain *chain)
 {
 	if (CHAIN_PINNED(chain)) {
 		chain->flags |= EVBUFFER_DANGLING;
 		return;
 	}
 	if (chain->flags & (EVBUFFER_MMAP|EVBUFFER_SENDFILE|
 		EVBUFFER_REFERENCE)) {
 		if (chain->flags & EVBUFFER_REFERENCE) {
 			struct evbuffer_chain_reference *info =
 			    EVBUFFER_CHAIN_EXTRA(
 				    struct evbuffer_chain_reference,
 				    chain);
 			if (info->cleanupfn)
 				(*info->cleanupfn)(chain->buffer,
 				    chain->buffer_len,
 				    info->extra);
 		}
 #ifdef _EVENT_HAVE_MMAP
 		if (chain->flags & EVBUFFER_MMAP) {
 			struct evbuffer_chain_fd *info =
 			    EVBUFFER_CHAIN_EXTRA(struct evbuffer_chain_fd,
 				chain);
 			if (munmap(chain->buffer, chain->buffer_len) == -1)
 				event_warn("%s: munmap failed", __func__);
 			if (close(info->fd) == -1)
 				event_warn("%s: close(%d) failed",
 				    __func__, info->fd);
 		}
 #endif
 #ifdef USE_SENDFILE
 		if (chain->flags & EVBUFFER_SENDFILE) {
 			struct evbuffer_chain_fd *info =
 			    EVBUFFER_CHAIN_EXTRA(struct evbuffer_chain_fd,
 				chain);
 			if (close(info->fd) == -1)
 				event_warn("%s: close(%d) failed",
 				    __func__, info->fd);
 		}
 #endif
 	}
 	mm_free(chain);
 }
 static void
 evbuffer_free_all_chains(struct evbuffer_chain *chain)
 {
 	struct evbuffer_chain *next;
 	for (; chain; chain = next) {
 		next = chain->next;
 		evbuffer_chain_free(chain);
 	}
 }
 #ifndef NDEBUG
 static int
 evbuffer_chains_all_empty(struct evbuffer_chain *chain)
 {
 	for (; chain; chain = chain->next) {
 		if (chain->off)
 			return 0;
 	}
 	return 1;
 }
 #else
 /* The definition is needed for EVUTIL_ASSERT, which uses sizeof to avoid
 "unused variable" warnings. */
 static inline int evbuffer_chains_all_empty(struct evbuffer_chain *chain) {
 	return 1;
 }
 #endif
 /* Free all trailing chains in 'buf' that are neither pinned nor empty, prior
  * to replacing them all with a new chain.  Return a pointer to the place
  * where the new chain will go.
  *
  * Internal; requires lock.  The caller must fix up buf->last and buf->first
  * as needed; they might have been freed.
  */
 static struct evbuffer_chain **
 evbuffer_free_trailing_empty_chains(struct evbuffer *buf)
 {
 	struct evbuffer_chain **ch = buf->last_with_datap;
 	/* Find the first victim chain.  It might be *last_with_datap */
 	while ((*ch) && ((*ch)->off != 0 || CHAIN_PINNED(*ch)))
 		ch = &(*ch)->next;
 	if (*ch) {
 		EVUTIL_ASSERT(evbuffer_chains_all_empty(*ch));
 		evbuffer_free_all_chains(*ch);
 		*ch = NULL;
 	}
 	return ch;
 }
 /* Add a single chain 'chain' to the end of 'buf', freeing trailing empty
  * chains as necessary.  Requires lock.  Does not schedule callbacks.
  */
 static void
 evbuffer_chain_insert(struct evbuffer *buf,
     struct evbuffer_chain *chain)
 {
 	ASSERT_EVBUFFER_LOCKED(buf);
 	if (*buf->last_with_datap == NULL) {
 		/* There are no chains data on the buffer at all. */
 		EVUTIL_ASSERT(buf->last_with_datap == &buf->first);
 		EVUTIL_ASSERT(buf->first == NULL);
 		buf->first = buf->last = chain;
 	} else {
 		struct evbuffer_chain **ch = buf->last_with_datap;
 		/* Find the first victim chain.  It might be *last_with_datap */
 		while ((*ch) && ((*ch)->off != 0 || CHAIN_PINNED(*ch)))
 			ch = &(*ch)->next;
 		if (*ch == NULL) {
 			/* There is no victim; just append this new chain. */
 			buf->last->next = chain;
 			if (chain->off)
 				buf->last_with_datap = &buf->last->next;
 		} else {
 			/* Replace all victim chains with this chain. */
 			EVUTIL_ASSERT(evbuffer_chains_all_empty(*ch));
 			evbuffer_free_all_chains(*ch);
 			*ch = chain;
 		}
 		buf->last = chain;
 	}
 	buf->total_len += chain->off;
 }
 static inline struct evbuffer_chain *
 evbuffer_chain_insert_new(struct evbuffer *buf, size_t datlen)
 {
 	struct evbuffer_chain *chain;
 	if ((chain = evbuffer_chain_new(datlen)) == NULL)
 		return NULL;
 	evbuffer_chain_insert(buf, chain);
 	return chain;
 }
 void
 _evbuffer_chain_pin(struct evbuffer_chain *chain, unsigned flag)
 {
 	EVUTIL_ASSERT((chain->flags & flag) == 0);
 	chain->flags |= flag;
 }
 void
 _evbuffer_chain_unpin(struct evbuffer_chain *chain, unsigned flag)
 {
 	EVUTIL_ASSERT((chain->flags & flag) != 0);
 	chain->flags &= ~flag;
 	if (chain->flags & EVBUFFER_DANGLING)
 		evbuffer_chain_free(chain);
 }
 struct evbuffer *
 evbuffer_new(void)
 {
 	struct evbuffer *buffer;
 	buffer = mm_calloc(1, sizeof(struct evbuffer));
 	if (buffer == NULL)
 		return (NULL);
 	TAILQ_INIT(&buffer->callbacks);
 	buffer->refcnt = 1;
 	buffer->last_with_datap = &buffer->first;
 	return (buffer);
 }
 int
 evbuffer_set_flags(struct evbuffer *buf, ev_uint64_t flags)
 {
 	EVBUFFER_LOCK(buf);
 	buf->flags |= (ev_uint32_t)flags;
 	EVBUFFER_UNLOCK(buf);
 	return 0;
 }
 int
 evbuffer_clear_flags(struct evbuffer *buf, ev_uint64_t flags)
 {
 	EVBUFFER_LOCK(buf);
 	buf->flags &= ~(ev_uint32_t)flags;
 	EVBUFFER_UNLOCK(buf);
 	return 0;
 }
 void
 _evbuffer_incref(struct evbuffer *buf)
 {
 	EVBUFFER_LOCK(buf);
 	++buf->refcnt;
 	EVBUFFER_UNLOCK(buf);
 }
 void
 _evbuffer_incref_and_lock(struct evbuffer *buf)
 {
 	EVBUFFER_LOCK(buf);
 	++buf->refcnt;
 }
 int
 evbuffer_defer_callbacks(struct evbuffer *buffer, struct event_base *base)
 {
 	EVBUFFER_LOCK(buffer);
 	buffer->cb_queue = event_base_get_deferred_cb_queue(base);
 	buffer->deferred_cbs = 1;
 	event_deferred_cb_init(&buffer->deferred,
 	    evbuffer_deferred_callback, buffer);
 	EVBUFFER_UNLOCK(buffer);
 	return 0;
 }
 int
 evbuffer_enable_locking(struct evbuffer *buf, void *lock)
 {
 #ifdef _EVENT_DISABLE_THREAD_SUPPORT
 	return -1;
 #else
 	if (buf->lock)
 		return -1;
 	if (!lock) {
 		EVTHREAD_ALLOC_LOCK(lock, EVTHREAD_LOCKTYPE_RECURSIVE);
 		if (!lock)
 			return -1;
 		buf->lock = lock;
 		buf->own_lock = 1;
 	} else {
 		buf->lock = lock;
 		buf->own_lock = 0;
 	}
 	return 0;
 #endif
 }
 void
 evbuffer_set_parent(struct evbuffer *buf, struct bufferevent *bev)
 {
 	EVBUFFER_LOCK(buf);
 	buf->parent = bev;
 	EVBUFFER_UNLOCK(buf);
 }
 static void
 evbuffer_run_callbacks(struct evbuffer *buffer, int running_deferred)
 {
 	struct evbuffer_cb_entry *cbent, *next;
 	struct evbuffer_cb_info info;
 	size_t new_size;
 	ev_uint32_t mask, masked_val;
 	int clear = 1;
 	if (running_deferred) {
 		mask = EVBUFFER_CB_NODEFER|EVBUFFER_CB_ENABLED;
 		masked_val = EVBUFFER_CB_ENABLED;
 	} else if (buffer->deferred_cbs) {
 		mask = EVBUFFER_CB_NODEFER|EVBUFFER_CB_ENABLED;
 		masked_val = EVBUFFER_CB_NODEFER|EVBUFFER_CB_ENABLED;
 		/* Don't zero-out n_add/n_del, since the deferred callbacks
 		   will want to see them. */
 		clear = 0;
 	} else {
 		mask = EVBUFFER_CB_ENABLED;
 		masked_val = EVBUFFER_CB_ENABLED;
 	}
 	ASSERT_EVBUFFER_LOCKED(buffer);
 	if (TAILQ_EMPTY(&buffer->callbacks)) {
 		buffer->n_add_for_cb = buffer->n_del_for_cb = 0;
 		return;
 	}
 	if (buffer->n_add_for_cb == 0 && buffer->n_del_for_cb == 0)
 		return;
 	new_size = buffer->total_len;
 	info.orig_size = new_size + buffer->n_del_for_cb - buffer->n_add_for_cb;
 	info.n_added = buffer->n_add_for_cb;
 	info.n_deleted = buffer->n_del_for_cb;
 	if (clear) {
 		buffer->n_add_for_cb = 0;
 		buffer->n_del_for_cb = 0;
 	}
 	for (cbent = TAILQ_FIRST(&buffer->callbacks);
 	     cbent != NULL;
 	     cbent = next) {
 		/* Get the 'next' pointer now in case this callback decides
 		 * to remove itself or something. */
 		next = TAILQ_NEXT(cbent, next);
 		if ((cbent->flags & mask) != masked_val)
 			continue;
 		if ((cbent->flags & EVBUFFER_CB_OBSOLETE))
 			cbent->cb.cb_obsolete(buffer,
 			    info.orig_size, new_size, cbent->cbarg);
 		else
 			cbent->cb.cb_func(buffer, &info, cbent->cbarg);
 	}
 }
 void
 evbuffer_invoke_callbacks(struct evbuffer *buffer)
 {
 	if (TAILQ_EMPTY(&buffer->callbacks)) {
 		buffer->n_add_for_cb = buffer->n_del_for_cb = 0;
 		return;
 	}
 	if (buffer->deferred_cbs) {
 		if (buffer->deferred.queued)
 			return;
 		_evbuffer_incref_and_lock(buffer);
 		if (buffer->parent)
 			bufferevent_incref(buffer->parent);
 		EVBUFFER_UNLOCK(buffer);
 		event_deferred_cb_schedule(buffer->cb_queue, &buffer->deferred);
 	}
 	evbuffer_run_callbacks(buffer, 0);
 }
 static void
 evbuffer_deferred_callback(struct deferred_cb *cb, void *arg)
 {
 	struct bufferevent *parent = NULL;
 	struct evbuffer *buffer = arg;
 	/* XXXX It would be better to run these callbacks without holding the
 	 * lock */
 	EVBUFFER_LOCK(buffer);
 	parent = buffer->parent;
 	evbuffer_run_callbacks(buffer, 1);
 	_evbuffer_decref_and_unlock(buffer);
 	if (parent)
 		bufferevent_decref(parent);
 }
 static void
 evbuffer_remove_all_callbacks(struct evbuffer *buffer)
 {
 	struct evbuffer_cb_entry *cbent;
 	while ((cbent = TAILQ_FIRST(&buffer->callbacks))) {
 	    TAILQ_REMOVE(&buffer->callbacks, cbent, next);
 	    mm_free(cbent);
 	}
 }
 void
 _evbuffer_decref_and_unlock(struct evbuffer *buffer)
 {
 	struct evbuffer_chain *chain, *next;
 	ASSERT_EVBUFFER_LOCKED(buffer);
 	EVUTIL_ASSERT(buffer->refcnt > 0);
 	if (--buffer->refcnt > 0) {
 		EVBUFFER_UNLOCK(buffer);
 		return;
 	}
 	for (chain = buffer->first; chain != NULL; chain = next) {
 		next = chain->next;
 		evbuffer_chain_free(chain);
 	}
 	evbuffer_remove_all_callbacks(buffer);
 	if (buffer->deferred_cbs)
 		event_deferred_cb_cancel(buffer->cb_queue, &buffer->deferred);
 	EVBUFFER_UNLOCK(buffer);
 	if (buffer->own_lock)
 		EVTHREAD_FREE_LOCK(buffer->lock, EVTHREAD_LOCKTYPE_RECURSIVE);
 	mm_free(buffer);
 }
 void
 evbuffer_free(struct evbuffer *buffer)
 {
 	EVBUFFER_LOCK(buffer);
 	_evbuffer_decref_and_unlock(buffer);
 }
 void
 evbuffer_lock(struct evbuffer *buf)
 {
 	EVBUFFER_LOCK(buf);
 }
 void
 evbuffer_unlock(struct evbuffer *buf)
 {
 	EVBUFFER_UNLOCK(buf);
 }
 size_t
 evbuffer_get_length(const struct evbuffer *buffer)
 {
 	size_t result;
 	EVBUFFER_LOCK(buffer);
 	result = (buffer->total_len);
 	EVBUFFER_UNLOCK(buffer);
 	return result;
 }
 size_t
 evbuffer_get_contiguous_space(const struct evbuffer *buf)
 {
 	struct evbuffer_chain *chain;
 	size_t result;
 	EVBUFFER_LOCK(buf);
 	chain = buf->first;
 	result = (chain != NULL ? chain->off : 0);
 	EVBUFFER_UNLOCK(buf);
 	return result;
 }
 int
 evbuffer_reserve_space(struct evbuffer *buf, ev_ssize_t size,
     struct evbuffer_iovec *vec, int n_vecs)
 {
 	struct evbuffer_chain *chain, **chainp;
 	int n = -1;
 	EVBUFFER_LOCK(buf);
 	if (buf->freeze_end)
 		goto done;
 	if (n_vecs < 1)
 		goto done;
 	if (n_vecs == 1) {
 		if ((chain = evbuffer_expand_singlechain(buf, size)) == NULL)
 			goto done;
 		vec[0].iov_base = CHAIN_SPACE_PTR(chain);
 		vec[0].iov_len = (size_t) CHAIN_SPACE_LEN(chain);
 		EVUTIL_ASSERT(size<0 || (size_t)vec[0].iov_len >= (size_t)size);
 		n = 1;
 	} else {
 		if (_evbuffer_expand_fast(buf, size, n_vecs)<0)
 			goto done;
 		n = _evbuffer_read_setup_vecs(buf, size, vec, n_vecs,
 				&chainp, 0);
 	}
 done:
 	EVBUFFER_UNLOCK(buf);
 	return n;
 }
 static int
 advance_last_with_data(struct evbuffer *buf)
 {
 	int n = 0;
 	ASSERT_EVBUFFER_LOCKED(buf);
 	if (!*buf->last_with_datap)
 		return 0;
 	while ((*buf->last_with_datap)->next && (*buf->last_with_datap)->next->off) {
 		buf->last_with_datap = &(*buf->last_with_datap)->next;
 		++n;
 	}
 	return n;
 }
 int
 evbuffer_commit_space(struct evbuffer *buf,
     struct evbuffer_iovec *vec, int n_vecs)
 {
 	struct evbuffer_chain *chain, **firstchainp, **chainp;
 	int result = -1;
 	size_t added = 0;
 	int i;
 	EVBUFFER_LOCK(buf);
 	if (buf->freeze_end)
 		goto done;
 	if (n_vecs == 0) {
 		result = 0;
 		goto done;
 	} else if (n_vecs == 1 &&
 	    (buf->last && vec[0].iov_base == (void*)CHAIN_SPACE_PTR(buf->last))) {
 		/* The user only got or used one chain; it might not
 		 * be the first one with space in it. */
 		if ((size_t)vec[0].iov_len > (size_t)CHAIN_SPACE_LEN(buf->last))
 			goto done;
 		buf->last->off += vec[0].iov_len;
 		added = vec[0].iov_len;
 		if (added)
 			advance_last_with_data(buf);
 		goto okay;
 	}
 	/* Advance 'firstchain' to the first chain with space in it. */
 	firstchainp = buf->last_with_datap;
 	if (!*firstchainp)
 		goto done;
 	if (CHAIN_SPACE_LEN(*firstchainp) == 0) {
 		firstchainp = &(*firstchainp)->next;
 	}
 	chain = *firstchainp;
 	/* pass 1: make sure that the pointers and lengths of vecs[] are in
 	 * bounds before we try to commit anything. */
 	for (i=0; i<n_vecs; ++i) {
 		if (!chain)
 			goto done;
 		if (vec[i].iov_base != (void*)CHAIN_SPACE_PTR(chain) ||
 		    (size_t)vec[i].iov_len > CHAIN_SPACE_LEN(chain))
 			goto done;
 		chain = chain->next;
 	}
 	/* pass 2: actually adjust all the chains. */
 	chainp = firstchainp;
 	for (i=0; i<n_vecs; ++i) {
 		(*chainp)->off += vec[i].iov_len;
 		added += vec[i].iov_len;
 		if (vec[i].iov_len) {
 			buf->last_with_datap = chainp;
 		}
 		chainp = &(*chainp)->next;
 	}
 okay:
 	buf->total_len += added;
 	buf->n_add_for_cb += added;
 	result = 0;
 	evbuffer_invoke_callbacks(buf);
 done:
 	EVBUFFER_UNLOCK(buf);
 	return result;
 }
 static inline int
 HAS_PINNED_R(struct evbuffer *buf)
 {
 	return (buf->last && CHAIN_PINNED_R(buf->last));
 }
 static inline void
 ZERO_CHAIN(struct evbuffer *dst)
 {
 	ASSERT_EVBUFFER_LOCKED(dst);
 	dst->first = NULL;
 	dst->last = NULL;
 	dst->last_with_datap = &(dst)->first;
 	dst->total_len = 0;
 }
 /* Prepares the contents of src to be moved to another buffer by removing
  * read-pinned chains. The first pinned chain is saved in first, and the
  * last in last. If src has no read-pinned chains, first and last are set
  * to NULL. */
 static int
 PRESERVE_PINNED(struct evbuffer *src, struct evbuffer_chain **first,
 		struct evbuffer_chain **last)
 {
 	struct evbuffer_chain *chain, **pinned;
 	ASSERT_EVBUFFER_LOCKED(src);
 	if (!HAS_PINNED_R(src)) {
 		*first = *last = NULL;
 		return 0;
 	}
 	pinned = src->last_with_datap;
 	if (!CHAIN_PINNED_R(*pinned))
 		pinned = &(*pinned)->next;
 	EVUTIL_ASSERT(CHAIN_PINNED_R(*pinned));
 	chain = *first = *pinned;
 	*last = src->last;
 	/* If there's data in the first pinned chain, we need to allocate
 	 * a new chain and copy the data over. */
 	if (chain->off) {
 		struct evbuffer_chain *tmp;
 		EVUTIL_ASSERT(pinned == src->last_with_datap);
 		tmp = evbuffer_chain_new(chain->off);
 		if (!tmp)
 			return -1;
 		memcpy(tmp->buffer, chain->buffer + chain->misalign,
 			chain->off);
 		tmp->off = chain->off;
 		*src->last_with_datap = tmp;
 		src->last = tmp;
 		chain->misalign += chain->off;
 		chain->off = 0;
 	} else {
 		src->last = *src->last_with_datap;
 		*pinned = NULL;
 	}
 	return 0;
 }
 static inline void
 RESTORE_PINNED(struct evbuffer *src, struct evbuffer_chain *pinned,
 		struct evbuffer_chain *last)
 {
 	ASSERT_EVBUFFER_LOCKED(src);
 	if (!pinned) {
 		ZERO_CHAIN(src);
 		return;
 	}
 	src->first = pinned;
 	src->last = last;
 	src->last_with_datap = &src->first;
 	src->total_len = 0;
 }
 static inline void
 COPY_CHAIN(struct evbuffer *dst, struct evbuffer *src)
 {
 	ASSERT_EVBUFFER_LOCKED(dst);
 	ASSERT_EVBUFFER_LOCKED(src);
 	dst->first = src->first;
 	if (src->last_with_datap == &src->first)
 		dst->last_with_datap = &dst->first;
 	else
 		dst->last_with_datap = src->last_with_datap;
 	dst->last = src->last;
 	dst->total_len = src->total_len;
 }
 static void
 APPEND_CHAIN(struct evbuffer *dst, struct evbuffer *src)
 {
 	ASSERT_EVBUFFER_LOCKED(dst);
 	ASSERT_EVBUFFER_LOCKED(src);
 	dst->last->next = src->first;
 	if (src->last_with_datap == &src->first)
 		dst->last_with_datap = &dst->last->next;
 	else
 		dst->last_with_datap = src->last_with_datap;
 	dst->last = src->last;
 	dst->total_len += src->total_len;
 }
 static void
 PREPEND_CHAIN(struct evbuffer *dst, struct evbuffer *src)
 {
 	ASSERT_EVBUFFER_LOCKED(dst);
 	ASSERT_EVBUFFER_LOCKED(src);
 	src->last->next = dst->first;
 	dst->first = src->first;
 	dst->total_len += src->total_len;
 	if (*dst->last_with_datap == NULL) {
 		if (src->last_with_datap == &(src)->first)
 			dst->last_with_datap = &dst->first;
 		else
 			dst->last_with_datap = src->last_with_datap;
 	} else if (dst->last_with_datap == &dst->first) {
 		dst->last_with_datap = &src->last->next;
 	}
 }
 int
 evbuffer_add_buffer(struct evbuffer *outbuf, struct evbuffer *inbuf)
 {
 	struct evbuffer_chain *pinned, *last;
 	size_t in_total_len, out_total_len;
 	int result = 0;
 	EVBUFFER_LOCK2(inbuf, outbuf);
 	in_total_len = inbuf->total_len;
 	out_total_len = outbuf->total_len;
 	if (in_total_len == 0 || outbuf == inbuf)
 		goto done;
 	if (outbuf->freeze_end || inbuf->freeze_start) {
 		result = -1;
 		goto done;
 	}
 	if (PRESERVE_PINNED(inbuf, &pinned, &last) < 0) {
 		result = -1;
 		goto done;
 	}
 	if (out_total_len == 0) {
 		/* There might be an empty chain at the start of outbuf; free
 		 * it. */
 		evbuffer_free_all_chains(outbuf->first);
 		COPY_CHAIN(outbuf, inbuf);
 	} else {
 		APPEND_CHAIN(outbuf, inbuf);
 	}
 	RESTORE_PINNED(inbuf, pinned, last);
 	inbuf->n_del_for_cb += in_total_len;
 	outbuf->n_add_for_cb += in_total_len;
 	evbuffer_invoke_callbacks(inbuf);
 	evbuffer_invoke_callbacks(outbuf);
 done:
 	EVBUFFER_UNLOCK2(inbuf, outbuf);
 	return result;
 }
 int
 evbuffer_prepend_buffer(struct evbuffer *outbuf, struct evbuffer *inbuf)
 {
 	struct evbuffer_chain *pinned, *last;
 	size_t in_total_len, out_total_len;
 	int result = 0;
 	EVBUFFER_LOCK2(inbuf, outbuf);
 	in_total_len = inbuf->total_len;
 	out_total_len = outbuf->total_len;
 	if (!in_total_len || inbuf == outbuf)
 		goto done;
 	if (outbuf->freeze_start || inbuf->freeze_start) {
 		result = -1;
 		goto done;
 	}
 	if (PRESERVE_PINNED(inbuf, &pinned, &last) < 0) {
 		result = -1;
 		goto done;
 	}
 	if (out_total_len == 0) {
 		/* There might be an empty chain at the start of outbuf; free
 		 * it. */
 		evbuffer_free_all_chains(outbuf->first);
 		COPY_CHAIN(outbuf, inbuf);
 	} else {
 		PREPEND_CHAIN(outbuf, inbuf);
 	}
 	RESTORE_PINNED(inbuf, pinned, last);
 	inbuf->n_del_for_cb += in_total_len;
 	outbuf->n_add_for_cb += in_total_len;
 	evbuffer_invoke_callbacks(inbuf);
 	evbuffer_invoke_callbacks(outbuf);
 done:
 	EVBUFFER_UNLOCK2(inbuf, outbuf);
 	return result;
 }
 int
 evbuffer_drain(struct evbuffer *buf, size_t len)
 {
 	struct evbuffer_chain *chain, *next;
 	size_t remaining, old_len;
 	int result = 0;
 	EVBUFFER_LOCK(buf);
 	old_len = buf->total_len;
 	if (old_len == 0)
 		goto done;
 	if (buf->freeze_start) {
 		result = -1;
 		goto done;
 	}
 	if (len >= old_len && !HAS_PINNED_R(buf)) {
 		len = old_len;
 		for (chain = buf->first; chain != NULL; chain = next) {
 			next = chain->next;
 			evbuffer_chain_free(chain);
 		}
 		ZERO_CHAIN(buf);
 	} else {
 		if (len >= old_len)
 			len = old_len;
 		buf->total_len -= len;
 		remaining = len;
 		for (chain = buf->first;
 		     remaining >= chain->off;
 		     chain = next) {
 			next = chain->next;
 			remaining -= chain->off;
 			if (chain == *buf->last_with_datap) {
 				buf->last_with_datap = &buf->first;
 			}
 			if (&chain->next == buf->last_with_datap)
 				buf->last_with_datap = &buf->first;
 			if (CHAIN_PINNED_R(chain)) {
 				EVUTIL_ASSERT(remaining == 0);
 				chain->misalign += chain->off;
 				chain->off = 0;
 				break;
 			} else
 				evbuffer_chain_free(chain);
 		}
 		buf->first = chain;
 		if (chain) {
 			chain->misalign += remaining;
 			chain->off -= remaining;
 		}
 	}
 	buf->n_del_for_cb += len;
 	/* Tell someone about changes in this buffer */
 	evbuffer_invoke_callbacks(buf);
 done:
 	EVBUFFER_UNLOCK(buf);
 	return result;
 }
 /* Reads data from an event buffer and drains the bytes read */
 int
 evbuffer_remove(struct evbuffer *buf, void *data_out, size_t datlen)
 {
 	ev_ssize_t n;
 	EVBUFFER_LOCK(buf);
 	n = evbuffer_copyout(buf, data_out, datlen);
 	if (n > 0) {
 		if (evbuffer_drain(buf, n)<0)
 			n = -1;
 	}
 	EVBUFFER_UNLOCK(buf);
 	return (int)n;
 }
 ev_ssize_t
 evbuffer_copyout(struct evbuffer *buf, void *data_out, size_t datlen)
 {
 	/*XXX fails badly on sendfile case. */
 	struct evbuffer_chain *chain;
 	char *data = data_out;
 	size_t nread;
 	ev_ssize_t result = 0;
 	EVBUFFER_LOCK(buf);
 	chain = buf->first;
 	if (datlen >= buf->total_len)
 		datlen = buf->total_len;
 	if (datlen == 0)
 		goto done;
 	if (buf->freeze_start) {
 		result = -1;
 		goto done;
 	}
 	nread = datlen;
 	while (datlen && datlen >= chain->off) {
 		memcpy(data, chain->buffer + chain->misalign, chain->off);
 		data += chain->off;
 		datlen -= chain->off;
 		chain = chain->next;
 		EVUTIL_ASSERT(chain || datlen==0);
 	}
 	if (datlen) {
 		EVUTIL_ASSERT(chain);
 		memcpy(data, chain->buffer + chain->misalign, datlen);
 	}
 	result = nread;
 done:
 	EVBUFFER_UNLOCK(buf);
 	return result;
 }
 /* reads data from the src buffer to the dst buffer, avoids memcpy as
  * possible. */
 /*  XXXX should return ev_ssize_t */
 int
 evbuffer_remove_buffer(struct evbuffer *src, struct evbuffer *dst,
     size_t datlen)
 {
 	/*XXX We should have an option to force this to be zero-copy.*/
 	/*XXX can fail badly on sendfile case. */
 	struct evbuffer_chain *chain, *previous;
 	size_t nread = 0;
 	int result;
 	EVBUFFER_LOCK2(src, dst);
 	chain = previous = src->first;
 	if (datlen == 0 || dst == src) {
 		result = 0;
 		goto done;
 	}
 	if (dst->freeze_end || src->freeze_start) {
 		result = -1;
 		goto done;
 	}
 	/* short-cut if there is no more data buffered */
 	if (datlen >= src->total_len) {
 		datlen = src->total_len;
 		evbuffer_add_buffer(dst, src);
 		result = (int)datlen; /*XXXX should return ev_ssize_t*/
 		goto done;
 	}
 	/* removes chains if possible */
 	while (chain->off <= datlen) {
 		/* We can't remove the last with data from src unless we
 		 * remove all chains, in which case we would have done the if
 		 * block above */
 		EVUTIL_ASSERT(chain != *src->last_with_datap);
 		nread += chain->off;
 		datlen -= chain->off;
 		previous = chain;
 		if (src->last_with_datap == &chain->next)
 			src->last_with_datap = &src->first;
 		chain = chain->next;
 	}
 	if (nread) {
 		/* we can remove the chain */
 		struct evbuffer_chain **chp;
 		chp = evbuffer_free_trailing_empty_chains(dst);
 		if (dst->first == NULL) {
 			dst->first = src->first;
 		} else {
 			*chp = src->first;
 		}
 		dst->last = previous;
 		previous->next = NULL;
 		src->first = chain;
 		advance_last_with_data(dst);
 		dst->total_len += nread;
 		dst->n_add_for_cb += nread;
 	}
 	/* we know that there is more data in the src buffer than
 	 * we want to read, so we manually drain the chain */
 	evbuffer_add(dst, chain->buffer + chain->misalign, datlen);
 	chain->misalign += datlen;
 	chain->off -= datlen;
 	nread += datlen;
 	/* You might think we would want to increment dst->n_add_for_cb
 	 * here too.  But evbuffer_add above already took care of that.
 	 */
 	src->total_len -= nread;
 	src->n_del_for_cb += nread;
 	if (nread) {
 		evbuffer_invoke_callbacks(dst);
 		evbuffer_invoke_callbacks(src);
 	}
 	result = (int)nread;/*XXXX should change return type */
 done:
 	EVBUFFER_UNLOCK2(src, dst);
 	return result;
 }
 unsigned char *
 evbuffer_pullup(struct evbuffer *buf, ev_ssize_t size)
 {
 	struct evbuffer_chain *chain, *next, *tmp, *last_with_data;
 	unsigned char *buffer, *result = NULL;
 	ev_ssize_t remaining;
 	int removed_last_with_data = 0;
 	int removed_last_with_datap = 0;
 	EVBUFFER_LOCK(buf);
 	chain = buf->first;
 	if (size < 0)
 		size = buf->total_len;
 	/* 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_t)size > buf->total_len)
 		goto done;
 	/* No need to pull up anything; the first size bytes are
 	 * already here. */
 	if (chain->off >= (size_t)size) {
 		result = chain->buffer + chain->misalign;
 		goto done;
 	}
 	/* Make sure that none of the chains we need to copy from is pinned. */
 	remaining = size - chain->off;
 	EVUTIL_ASSERT(remaining >= 0);
 	for (tmp=chain->next; tmp; tmp=tmp->next) {
 		if (CHAIN_PINNED(tmp))
 			goto done;
 		if (tmp->off >= (size_t)remaining)
 			break;
 		remaining -= tmp->off;
 	}
 	if (CHAIN_PINNED(chain)) {
 		size_t old_off = chain->off;
 		if (CHAIN_SPACE_LEN(chain) < size - chain->off) {
 			/* not enough room at end of chunk. */
 			goto done;
 		}
 		buffer = CHAIN_SPACE_PTR(chain);
 		tmp = chain;
 		tmp->off = size;
 		size -= old_off;
 		chain = chain->next;
 	} else if (chain->buffer_len - chain->misalign >= (size_t)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", __func__);
 			goto done;
 		}
 		buffer = tmp->buffer;
 		tmp->off = size;
 		buf->first = tmp;
 	}
 	/* TODO(niels): deal with buffers that point to NULL like sendfile */
 	/* Copy and free every chunk that will be entirely pulled into tmp */
 	last_with_data = *buf->last_with_datap;
 	for (; chain != NULL && (size_t)size >= chain->off; chain = next) {
 		next = chain->next;
 		memcpy(buffer, chain->buffer + chain->misalign, chain->off);
 		size -= chain->off;
 		buffer += chain->off;
 		if (chain == last_with_data)
 			removed_last_with_data = 1;
 		if (&chain->next == buf->last_with_datap)
 			removed_last_with_datap = 1;
 		evbuffer_chain_free(chain);
 	}
 	if (chain != NULL) {
 		memcpy(buffer, chain->buffer + chain->misalign, size);
 		chain->misalign += size;
 		chain->off -= size;
 	} else {
 		buf->last = tmp;
 	}
 	tmp->next = chain;
 	if (removed_last_with_data) {
 		buf->last_with_datap = &buf->first;
 	} else if (removed_last_with_datap) {
 		if (buf->first->next && buf->first->next->off)
 			buf->last_with_datap = &buf->first->next;
 		else
 			buf->last_with_datap = &buf->first;
 	}
 	result = (tmp->buffer + tmp->misalign);
 done:
 	EVBUFFER_UNLOCK(buf);
 	return result;
 }
 /*
  * Reads a line terminated by either '\r\n', '\n\r' or '\r' or '\n'.
  * The returned buffer needs to be freed by the called.
  */
 char *
 evbuffer_readline(struct evbuffer *buffer)
 {
 	return evbuffer_readln(buffer, NULL, EVBUFFER_EOL_ANY);
 }
 static inline ev_ssize_t
 evbuffer_strchr(struct evbuffer_ptr *it, const char chr)
 {
 	struct evbuffer_chain *chain = it->_internal.chain;
 	size_t i = it->_internal.pos_in_chain;
 	while (chain != NULL) {
 		char *buffer = (char *)chain->buffer + chain->misalign;
 		char *cp = memchr(buffer+i, chr, chain->off-i);
 		if (cp) {
 			it->_internal.chain = chain;
 			it->_internal.pos_in_chain = cp - buffer;
 			it->pos += (cp - buffer - i);
 			return it->pos;
 		}
 		it->pos += chain->off - i;
 		i = 0;
 		chain = chain->next;
 	}
 	return (-1);
 }
 static inline char *
 find_eol_char(char *s, size_t len)
 {
 #define CHUNK_SZ 128
 	/* Lots of benchmarking found this approach to be faster in practice
 	 * than doing two memchrs over the whole buffer, doin a memchr on each
 	 * char of the buffer, or trying to emulate memchr by hand. */
 	char *s_end, *cr, *lf;
 	s_end = s+len;
 	while (s < s_end) {
 		size_t chunk = (s + CHUNK_SZ < s_end) ? CHUNK_SZ : (s_end - s);
 		cr = memchr(s, '\r', chunk);
 		lf = memchr(s, '\n', chunk);
 		if (cr) {
 			if (lf && lf < cr)
 				return lf;
 			return cr;
 		} else if (lf) {
 			return lf;
 		}
 		s += CHUNK_SZ;
 	}
 	return NULL;
 #undef CHUNK_SZ
 }
 static ev_ssize_t
 evbuffer_find_eol_char(struct evbuffer_ptr *it)
 {
 	struct evbuffer_chain *chain = it->_internal.chain;
 	size_t i = it->_internal.pos_in_chain;
 	while (chain != NULL) {
 		char *buffer = (char *)chain->buffer + chain->misalign;
 		char *cp = find_eol_char(buffer+i, chain->off-i);
 		if (cp) {
 			it->_internal.chain = chain;
 			it->_internal.pos_in_chain = cp - buffer;
 			it->pos += (cp - buffer) - i;
 			return it->pos;
 		}
 		it->pos += chain->off - i;
 		i = 0;
 		chain = chain->next;
 	}
 	return (-1);
 }
 static inline int
 evbuffer_strspn(
 	struct evbuffer_ptr *ptr, const char *chrset)
 {
 	int count = 0;
 	struct evbuffer_chain *chain = ptr->_internal.chain;
 	size_t i = ptr->_internal.pos_in_chain;
 	if (!chain)
 		return -1;
 	while (1) {
 		char *buffer = (char *)chain->buffer + chain->misalign;
 		for (; i < chain->off; ++i) {
 			const char *p = chrset;
 			while (*p) {
 				if (buffer[i] == *p++)
 					goto next;
 			}
 			ptr->_internal.chain = chain;
 			ptr->_internal.pos_in_chain = i;
 			ptr->pos += count;
 			return count;
 		next:
 			++count;
 		}
 		i = 0;
 		if (! chain->next) {
 			ptr->_internal.chain = chain;
 			ptr->_internal.pos_in_chain = i;
 			ptr->pos += count;
 			return count;
 		}
 		chain = chain->next;
 	}
 }
 static inline char
 evbuffer_getchr(struct evbuffer_ptr *it)
 {
 	struct evbuffer_chain *chain = it->_internal.chain;
 	size_t off = it->_internal.pos_in_chain;
 	return chain->buffer[chain->misalign + off];
 }
 struct evbuffer_ptr
 evbuffer_search_eol(struct evbuffer *buffer,
     struct evbuffer_ptr *start, size_t *eol_len_out,
     enum evbuffer_eol_style eol_style)
 {
 	struct evbuffer_ptr it, it2;
 	size_t extra_drain = 0;
 	int ok = 0;
 	EVBUFFER_LOCK(buffer);
 	if (start) {
 		memcpy(&it, start, sizeof(it));
 	} else {
 		it.pos = 0;
 		it._internal.chain = buffer->first;
 		it._internal.pos_in_chain = 0;
 	}
 	/* the eol_style determines our first stop character and how many
 	 * characters we are going to drain afterwards. */
 	switch (eol_style) {
 	case EVBUFFER_EOL_ANY:
 		if (evbuffer_find_eol_char(&it) < 0)
 			goto done;
 		memcpy(&it2, &it, sizeof(it));
 		extra_drain = evbuffer_strspn(&it2, "\r\n");
 		break;
 	case EVBUFFER_EOL_CRLF_STRICT: {
 		it = evbuffer_search(buffer, "\r\n", 2, &it);
 		if (it.pos < 0)
 			goto done;
 		extra_drain = 2;
 		break;
 	}
 	case EVBUFFER_EOL_CRLF:
 		while (1) {
 			if (evbuffer_find_eol_char(&it) < 0)
 				goto done;
 			if (evbuffer_getchr(&it) == '\n') {
 				extra_drain = 1;
 				break;
 			} else if (!evbuffer_ptr_memcmp(
 				    buffer, &it, "\r\n", 2)) {
 				extra_drain = 2;
 				break;
 			} else {
 				if (evbuffer_ptr_set(buffer, &it, 1,
 					EVBUFFER_PTR_ADD)<0)
 					goto done;
 			}
 		}
 		break;
 	case EVBUFFER_EOL_LF:
 		if (evbuffer_strchr(&it, '\n') < 0)
 			goto done;
 		extra_drain = 1;
 		break;
 	default:
 		goto done;
 	}
 	ok = 1;
 done:
 	EVBUFFER_UNLOCK(buffer);
 	if (!ok) {
 		it.pos = -1;
 	}
 	if (eol_len_out)
 		*eol_len_out = extra_drain;
 	return it;
 }
 char *
 evbuffer_readln(struct evbuffer *buffer, size_t *n_read_out,
 		enum evbuffer_eol_style eol_style)
 {
 	struct evbuffer_ptr it;
 	char *line;
 	size_t n_to_copy=0, extra_drain=0;
 	char *result = NULL;
 	EVBUFFER_LOCK(buffer);
 	if (buffer->freeze_start) {
 		goto done;
 	}
 	it = evbuffer_search_eol(buffer, NULL, &extra_drain, eol_style);
 	if (it.pos < 0)
 		goto done;
 	n_to_copy = it.pos;
 	if ((line = mm_malloc(n_to_copy+1)) == NULL) {
 		event_warn("%s: out of memory", __func__);
 		goto done;
 	}
 	evbuffer_remove(buffer, line, n_to_copy);
 	line[n_to_copy] = '\0';
 	evbuffer_drain(buffer, extra_drain);
 	result = line;
 done:
 	EVBUFFER_UNLOCK(buffer);
 	if (n_read_out)
 		*n_read_out = result ? n_to_copy : 0;
 	return result;
 }
 #define EVBUFFER_CHAIN_MAX_AUTO_SIZE 4096
 /* Adds data to an event buffer */
 int
 evbuffer_add(struct evbuffer *buf, const void *data_in, size_t datlen)
 {
 	struct evbuffer_chain *chain, *tmp;
 	const unsigned char *data = data_in;
 	size_t remain, to_alloc;
 	int result = -1;
 	EVBUFFER_LOCK(buf);
 	if (buf->freeze_end) {
 		goto done;
 	}
 	chain = buf->last;
 	/* If there are no chains allocated for this buffer, allocate one
 	 * big enough to hold all the data. */
 	if (chain == NULL) {
 		chain = evbuffer_chain_new(datlen);
 		if (!chain)
 			goto done;
 		evbuffer_chain_insert(buf, chain);
 	}
 	if ((chain->flags & EVBUFFER_IMMUTABLE) == 0) {
 		remain = (size_t)(chain->buffer_len - chain->misalign - chain->off);
 		if (remain >= datlen) {
 			/* there's enough space to hold all the data in the
 			 * current last chain */
 			memcpy(chain->buffer + chain->misalign + chain->off,
 			    data, datlen);
 			chain->off += datlen;
 			buf->total_len += datlen;
 			buf->n_add_for_cb += datlen;
 			goto out;
 		} else if (!CHAIN_PINNED(chain) &&
 		    evbuffer_chain_should_realign(chain, datlen)) {
 			/* we can fit the data into the misalignment */
 			evbuffer_chain_align(chain);
 			memcpy(chain->buffer + chain->off, data, datlen);
 			chain->off += datlen;
 			buf->total_len += datlen;
 			buf->n_add_for_cb += datlen;
 			goto out;
 		}
 	} else {
 		/* we cannot write any data to the last chain */
 		remain = 0;
 	}
 	/* we need to add another chain */
 	to_alloc = chain->buffer_len;
 	if (to_alloc <= EVBUFFER_CHAIN_MAX_AUTO_SIZE/2)
 		to_alloc <<= 1;
 	if (datlen > to_alloc)
 		to_alloc = datlen;
 	tmp = evbuffer_chain_new(to_alloc);
 	if (tmp == NULL)
 		goto done;
 	if (remain) {
 		memcpy(chain->buffer + chain->misalign + chain->off,
 		    data, remain);
 		chain->off += remain;
 		buf->total_len += remain;
 		buf->n_add_for_cb += remain;
 	}
 	data += remain;
 	datlen -= remain;
 	memcpy(tmp->buffer, data, datlen);
 	tmp->off = datlen;
 	evbuffer_chain_insert(buf, tmp);
 	buf->n_add_for_cb += datlen;
 out:
 	evbuffer_invoke_callbacks(buf);
 	result = 0;
 done:
 	EVBUFFER_UNLOCK(buf);
 	return result;
 }
 int
 evbuffer_prepend(struct evbuffer *buf, const void *data, size_t datlen)
 {
 	struct evbuffer_chain *chain, *tmp;
 	int result = -1;
 	EVBUFFER_LOCK(buf);
 	if (buf->freeze_start) {
 		goto done;
 	}
 	chain = buf->first;
 	if (chain == NULL) {
 		chain = evbuffer_chain_new(datlen);
 		if (!chain)
 			goto done;
 		evbuffer_chain_insert(buf, chain);
 	}
 	/* we cannot touch immutable buffers */
 	if ((chain->flags & EVBUFFER_IMMUTABLE) == 0) {
 		/* If this chain is empty, we can treat it as
 		 * 'empty at the beginning' rather than 'empty at the end' */
 		if (chain->off == 0)
 			chain->misalign = chain->buffer_len;
 		if ((size_t)chain->misalign >= datlen) {
 			/* we have enough space to fit everything */
 			memcpy(chain->buffer + chain->misalign - datlen,
 			    data, datlen);
 			chain->off += datlen;
 			chain->misalign -= datlen;
 			buf->total_len += datlen;
 			buf->n_add_for_cb += datlen;
 			goto out;
 		} else if (chain->misalign) {
 			/* we can only fit some of the data. */
 			memcpy(chain->buffer,
 			    (char*)data + datlen - chain->misalign,
 			    (size_t)chain->misalign);
 			chain->off += (size_t)chain->misalign;
 			buf->total_len += (size_t)chain->misalign;
 			buf->n_add_for_cb += (size_t)chain->misalign;
 			datlen -= (size_t)chain->misalign;
 			chain->misalign = 0;
 		}
 	}
 	/* we need to add another chain */
 	if ((tmp = evbuffer_chain_new(datlen)) == NULL)
 		goto done;
 	buf->first = tmp;
 	if (buf->last_with_datap == &buf->first)
 		buf->last_with_datap = &tmp->next;
 	tmp->next = chain;
 	tmp->off = datlen;
 	tmp->misalign = tmp->buffer_len - datlen;
 	memcpy(tmp->buffer + tmp->misalign, data, datlen);
 	buf->total_len += datlen;
 	buf->n_add_for_cb += (size_t)chain->misalign;
 out:
 	evbuffer_invoke_callbacks(buf);
 	result = 0;
 done:
 	EVBUFFER_UNLOCK(buf);
 	return result;
 }
 /** Helper: realigns the memory in chain->buffer so that misalign is 0. */
 static void
 evbuffer_chain_align(struct evbuffer_chain *chain)
 {
 	EVUTIL_ASSERT(!(chain->flags & EVBUFFER_IMMUTABLE));
 	EVUTIL_ASSERT(!(chain->flags & EVBUFFER_MEM_PINNED_ANY));
 	memmove(chain->buffer, chain->buffer + chain->misalign, chain->off);
 	chain->misalign = 0;
 }
 #define MAX_TO_COPY_IN_EXPAND 4096
 #define MAX_TO_REALIGN_IN_EXPAND 2048
 /** Helper: return true iff we should realign chain to fit datalen bytes of
     data in it. */
 static int
 evbuffer_chain_should_realign(struct evbuffer_chain *chain,
     size_t datlen)
 {
 	return chain->buffer_len - chain->off >= datlen &&
 	    (chain->off < chain->buffer_len / 2) &&
 	    (chain->off <= MAX_TO_REALIGN_IN_EXPAND);
 }
 /* Expands the available space in the event buffer to at least datlen, all in
  * a single chunk.  Return that chunk. */
 static struct evbuffer_chain *
 evbuffer_expand_singlechain(struct evbuffer *buf, size_t datlen)
 {
 	struct evbuffer_chain *chain, **chainp;
 	struct evbuffer_chain *result = NULL;
 	ASSERT_EVBUFFER_LOCKED(buf);
 	chainp = buf->last_with_datap;
 	/* XXX If *chainp is no longer writeable, but has enough space in its
 	 * misalign, this might be a bad idea: we could still use *chainp, not
 	 * (*chainp)->next. */
 	if (*chainp && CHAIN_SPACE_LEN(*chainp) == 0)
 		chainp = &(*chainp)->next;
 	/* 'chain' now points to the first chain with writable space (if any)
 	 * We will either use it, realign it, replace it, or resize it. */
 	chain = *chainp;
 	if (chain == NULL ||
 	    (chain->flags & (EVBUFFER_IMMUTABLE|EVBUFFER_MEM_PINNED_ANY))) {
 		/* We can't use the last_with_data chain at all.  Just add a
 		 * new one that's big enough. */
 		goto insert_new;
 	}
 	/* If we can fit all the data, then we don't have to do anything */
 	if (CHAIN_SPACE_LEN(chain) >= datlen) {
 		result = chain;
 		goto ok;
 	}
 	/* If the chain is completely empty, just replace it by adding a new
 	 * empty chain. */
 	if (chain->off == 0) {
 		goto insert_new;
 	}
 	/* If the misalignment plus the remaining space fulfills our data
 	 * needs, we could just force an alignment to happen.  Afterwards, we
 	 * have enough space.  But only do this if we're saving a lot of space
 	 * and not moving too much data.  Otherwise the space savings are
 	 * probably offset by the time lost in copying.
 	 */
 	if (evbuffer_chain_should_realign(chain, datlen)) {
 		evbuffer_chain_align(chain);
 		result = chain;
 		goto ok;
 	}
 	/* At this point, we can either resize the last chunk with space in
 	 * it, use the next chunk after it, or   If we add a new chunk, we waste
 	 * CHAIN_SPACE_LEN(chain) bytes in the former last chunk.  If we
 	 * resize, we have to copy chain->off bytes.
 	 */
 	/* Would expanding this chunk be affordable and worthwhile? */
 	if (CHAIN_SPACE_LEN(chain) < chain->buffer_len / 8 ||
 	    chain->off > MAX_TO_COPY_IN_EXPAND) {
 		/* It's not worth resizing this chain. Can the next one be
 		 * used? */
 		if (chain->next && CHAIN_SPACE_LEN(chain->next) >= datlen) {
 			/* Yes, we can just use the next chain (which should
 			 * be empty. */
 			result = chain->next;
 			goto ok;
 		} else {
 			/* No; append a new chain (which will free all
 			 * terminal empty chains.) */
 			goto insert_new;
 		}
 	} else {
 		/* Okay, we're going to try to resize this chain: Not doing so
 		 * would waste at least 1/8 of its current allocation, and we
 		 * can do so without having to copy more than
 		 * MAX_TO_COPY_IN_EXPAND bytes. */
 		/* figure out how much space we need */
 		size_t length = chain->off + datlen;
 		struct evbuffer_chain *tmp = evbuffer_chain_new(length);
 		if (tmp == NULL)
 			goto err;
 		/* copy the data over that we had so far */
 		tmp->off = chain->off;
 		memcpy(tmp->buffer, chain->buffer + chain->misalign,
 		    chain->off);
 		/* fix up the list */
 		EVUTIL_ASSERT(*chainp == chain);
 		result = *chainp = tmp;
 		if (buf->last == chain)
 			buf->last = tmp;
 		tmp->next = chain->next;
 		evbuffer_chain_free(chain);
 		goto ok;
 	}
 insert_new:
 	result = evbuffer_chain_insert_new(buf, datlen);
 	if (!result)
 		goto err;
 ok:
 	EVUTIL_ASSERT(result);
 	EVUTIL_ASSERT(CHAIN_SPACE_LEN(result) >= datlen);
 err:
 	return result;
 }
 /* Make sure that datlen bytes are available for writing in the last n
  * chains.  Never copies or moves data. */
 int
 _evbuffer_expand_fast(struct evbuffer *buf, size_t datlen, int n)
 {
 	struct evbuffer_chain *chain = buf->last, *tmp, *next;
 	size_t avail;
 	int used;
 	ASSERT_EVBUFFER_LOCKED(buf);
 	EVUTIL_ASSERT(n >= 2);
 	if (chain == NULL || (chain->flags & EVBUFFER_IMMUTABLE)) {
 		/* There is no last chunk, or we can't touch the last chunk.
 		 * Just add a new chunk. */
 		chain = evbuffer_chain_new(datlen);
 		if (chain == NULL)
 			return (-1);
 		evbuffer_chain_insert(buf, chain);
 		return (0);
 	}
 	used = 0; /* number of chains we're using space in. */
 	avail = 0; /* how much space they have. */
 	/* How many bytes can we stick at the end of buffer as it is?  Iterate
 	 * over the chains at the end of the buffer, tring to see how much
 	 * space we have in the first n. */
 	for (chain = *buf->last_with_datap; chain; chain = chain->next) {
 		if (chain->off) {
 			size_t space = (size_t) CHAIN_SPACE_LEN(chain);
 			EVUTIL_ASSERT(chain == *buf->last_with_datap);
 			if (space) {
 				avail += space;
 				++used;
 			}
 		} else {
 			/* No data in chain; realign it. */
 			chain->misalign = 0;
 			avail += chain->buffer_len;
 			++used;
 		}
 		if (avail >= datlen) {
 			/* There is already enough space.  Just return */
 			return (0);
 		}
 		if (used == n)
 			break;
 	}
 	/* There wasn't enough space in the first n chains with space in
 	 * them. Either add a new chain with enough space, or replace all
 	 * empty chains with one that has enough space, depending on n. */
 	if (used < n) {
 		/* The loop ran off the end of the chains before it hit n
 		 * chains; we can add another. */
 		EVUTIL_ASSERT(chain == NULL);
 		tmp = evbuffer_chain_new(datlen - avail);
 		if (tmp == NULL)
 			return (-1);
 		buf->last->next = tmp;
 		buf->last = tmp;
 		/* (we would only set last_with_data if we added the first
 		 * chain. But if the buffer had no chains, we would have
 		 * just allocated a new chain earlier) */
 		return (0);
 	} else {
 		/* Nuke _all_ the empty chains. */
 		int rmv_all = 0; /* True iff we removed last_with_data. */
 		chain = *buf->last_with_datap;
 		if (!chain->off) {
 			EVUTIL_ASSERT(chain == buf->first);
 			rmv_all = 1;
 			avail = 0;
 		} else {
 			avail = (size_t) CHAIN_SPACE_LEN(chain);
 			chain = chain->next;
 		}
 		for (; chain; chain = next) {
 			next = chain->next;
 			EVUTIL_ASSERT(chain->off == 0);
 			evbuffer_chain_free(chain);
 		}
 		tmp = evbuffer_chain_new(datlen - avail);
 		if (tmp == NULL) {
 			if (rmv_all) {
 				ZERO_CHAIN(buf);
 			} else {
 				buf->last = *buf->last_with_datap;
 				(*buf->last_with_datap)->next = NULL;
 			}
 			return (-1);
 		}
 		if (rmv_all) {
 			buf->first = buf->last = tmp;
 			buf->last_with_datap = &buf->first;
 		} else {
 			(*buf->last_with_datap)->next = tmp;
 			buf->last = tmp;
 		}
 		return (0);
 	}
 }
 int
 evbuffer_expand(struct evbuffer *buf, size_t datlen)
 {
 	struct evbuffer_chain *chain;
 	EVBUFFER_LOCK(buf);
 	chain = evbuffer_expand_singlechain(buf, datlen);
 	EVBUFFER_UNLOCK(buf);
 	return chain ? 0 : -1;
 }
 /*
  * Reads data from a file descriptor into a buffer.
  */
 #if defined(_EVENT_HAVE_SYS_UIO_H) || defined(WIN32)
 #define USE_IOVEC_IMPL
 #endif
 #ifdef USE_IOVEC_IMPL
 #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 DEFAULT_WRITE_IOVEC 128
 #if defined(UIO_MAXIOV) && UIO_MAXIOV < DEFAULT_WRITE_IOVEC
 #define NUM_WRITE_IOVEC UIO_MAXIOV
 #elif defined(IOV_MAX) && IOV_MAX < DEFAULT_WRITE_IOVEC
 #define NUM_WRITE_IOVEC IOV_MAX
 #else
 #define NUM_WRITE_IOVEC DEFAULT_WRITE_IOVEC
 #endif
 #define IOV_TYPE struct iovec
 #define IOV_PTR_FIELD iov_base
 #define IOV_LEN_FIELD iov_len
 #define IOV_LEN_TYPE size_t
 #else
 #define NUM_WRITE_IOVEC 16
 #define IOV_TYPE WSABUF
 #define IOV_PTR_FIELD buf
 #define IOV_LEN_FIELD len
 #define IOV_LEN_TYPE unsigned long
 #endif
 #endif
 #define NUM_READ_IOVEC 4
 #define EVBUFFER_MAX_READ	4096
 /** Helper function to figure out which space to use for reading data into
     an evbuffer.  Internal use only.
     @param buf The buffer to read into
     @param howmuch How much we want to read.
     @param vecs An array of two or more iovecs or WSABUFs.
     @param n_vecs_avail The length of vecs
     @param chainp A pointer to a variable to hold the first chain we're
       reading into.
     @param exact Boolean: if true, we do not provide more than 'howmuch'
       space in the vectors, even if more space is available.
     @return The number of buffers we're using.
  */
 int
 _evbuffer_read_setup_vecs(struct evbuffer *buf, ev_ssize_t howmuch,
     struct evbuffer_iovec *vecs, int n_vecs_avail,
     struct evbuffer_chain ***chainp, int exact)
 {
 	struct evbuffer_chain *chain;
 	struct evbuffer_chain **firstchainp;
 	size_t so_far;
 	int i;
 	ASSERT_EVBUFFER_LOCKED(buf);
 	if (howmuch < 0)
 		return -1;
 	so_far = 0;
 	/* Let firstchain be the first chain with any space on it */
 	firstchainp = buf->last_with_datap;
 	if (CHAIN_SPACE_LEN(*firstchainp) == 0) {
 		firstchainp = &(*firstchainp)->next;
 	}
 	chain = *firstchainp;
 	for (i = 0; i < n_vecs_avail && so_far < (size_t)howmuch; ++i) {
 		size_t avail = (size_t) CHAIN_SPACE_LEN(chain);
 		if (avail > (howmuch - so_far) && exact)
 			avail = howmuch - so_far;
 		vecs[i].iov_base = CHAIN_SPACE_PTR(chain);
 		vecs[i].iov_len = avail;
 		so_far += avail;
 		chain = chain->next;
 	}
 	*chainp = firstchainp;
 	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 **chainp;
 	int n;
 	int result;
 #ifdef USE_IOVEC_IMPL
 	int nvecs, i, remaining;
 #else
 	struct evbuffer_chain *chain;
 	unsigned char *p;
 #endif
 	EVBUFFER_LOCK(buf);
 	if (buf->freeze_end) {
 		result = -1;
 		goto done;
 	}
 	n = get_n_bytes_readable_on_socket(fd);
 	if (n <= 0 || n > EVBUFFER_MAX_READ)
 		n = EVBUFFER_MAX_READ;
 	if (howmuch < 0 || howmuch > n)
 		howmuch = n;
 #ifdef USE_IOVEC_IMPL
 	/* Since we can use iovecs, we're willing to use the last
 	 * NUM_READ_IOVEC chains. */
 	if (_evbuffer_expand_fast(buf, howmuch, NUM_READ_IOVEC) == -1) {
 		result = -1;
 		goto done;
 	} else {
 		IOV_TYPE vecs[NUM_READ_IOVEC];
 #ifdef _EVBUFFER_IOVEC_IS_NATIVE
 		nvecs = _evbuffer_read_setup_vecs(buf, howmuch, vecs,
 		    NUM_READ_IOVEC, &chainp, 1);
 #else
 		/* We aren't using the native struct iovec.  Therefore,
 		   we are on win32. */
 		struct evbuffer_iovec ev_vecs[NUM_READ_IOVEC];
 		nvecs = _evbuffer_read_setup_vecs(buf, howmuch, ev_vecs, 2,
 		    &chainp, 1);
 		for (i=0; i < nvecs; ++i)
 			WSABUF_FROM_EVBUFFER_IOV(&vecs[i], &ev_vecs[i]);
 #endif
 #ifdef WIN32
 		{
 			DWORD bytesRead;
 			DWORD flags=0;
 			if (WSARecv(fd, vecs, nvecs, &bytesRead, &flags, NULL, NULL)) {
 				/* The read failed. It might be a close,
 				 * or it might be an error. */
 				if (WSAGetLastError() == WSAECONNABORTED)
 					n = 0;
 				else
 					n = -1;
 			} else
 				n = bytesRead;
 		}
 #else
 		n = readv(fd, vecs, nvecs);
 #endif
 	}
 #else /*!USE_IOVEC_IMPL*/
 	/* If we don't have FIONREAD, we might waste some space here */
 	/* XXX we _will_ waste some space here if there is any space left
 	 * over on buf->last. */
 	if ((chain = evbuffer_expand_singlechain(buf, howmuch)) == NULL) {
 		result = -1;
 		goto done;
 	}
 	/* We can append new data at this point */
 	p = chain->buffer + chain->misalign + chain->off;
 #ifndef WIN32
 	n = read(fd, p, howmuch);
 #else
 	n = recv(fd, p, howmuch, 0);
 #endif
 #endif /* USE_IOVEC_IMPL */
 	if (n == -1) {
 		result = -1;
 		goto done;
 	}
 	if (n == 0) {
 		result = 0;
 		goto done;
 	}
 #ifdef USE_IOVEC_IMPL
 	remaining = n;
 	for (i=0; i < nvecs; ++i) {
 		ev_ssize_t space = (ev_ssize_t) CHAIN_SPACE_LEN(*chainp);
 		if (space < remaining) {
 			(*chainp)->off += space;
 			remaining -= (int)space;
 		} else {
 			(*chainp)->off += remaining;
 			buf->last_with_datap = chainp;
 			break;
 		}
 		chainp = &(*chainp)->next;
 	}
 #else
 	chain->off += n;
 	advance_last_with_data(buf);
 #endif
 	buf->total_len += n;
 	buf->n_add_for_cb += n;
 	/* Tell someone about changes in this buffer */
 	evbuffer_invoke_callbacks(buf);
 	result = n;
 done:
 	EVBUFFER_UNLOCK(buf);
 	return result;
 }
 #ifdef WIN32
 static int
 evbuffer_readfile(struct evbuffer *buf, evutil_socket_t fd, ev_ssize_t howmuch)
 {
 	int result;
 	int nchains, n;
 	struct evbuffer_iovec v[2];
 	EVBUFFER_LOCK(buf);
 	if (buf->freeze_end) {
 		result = -1;
 		goto done;
 	}
 	if (howmuch < 0)
 		howmuch = 16384;
 	/* XXX we _will_ waste some space here if there is any space left
 	 * over on buf->last. */
 	nchains = evbuffer_reserve_space(buf, howmuch, v, 2);
 	if (nchains < 1 || nchains > 2) {
 		result = -1;
 		goto done;
 	}
 	n = read((int)fd, v[0].iov_base, (unsigned int)v[0].iov_len);
 	if (n <= 0) {
 		result = n;
 		goto done;
 	}
 	v[0].iov_len = (IOV_LEN_TYPE) n; /* XXXX another problem with big n.*/
 	if (nchains > 1) {
 		n = read((int)fd, v[1].iov_base, (unsigned int)v[1].iov_len);
 		if (n <= 0) {
 			result = (unsigned long) v[0].iov_len;
 			evbuffer_commit_space(buf, v, 1);
 			goto done;
 		}
 		v[1].iov_len = n;
 	}
 	evbuffer_commit_space(buf, v, nchains);
 	result = n;
 done:
 	EVBUFFER_UNLOCK(buf);
 	return result;
 }
 #endif
 #ifdef USE_IOVEC_IMPL
 static inline int
 evbuffer_write_iovec(struct evbuffer *buffer, evutil_socket_t fd,
     ev_ssize_t howmuch)
 {
 	IOV_TYPE iov[NUM_WRITE_IOVEC];
 	struct evbuffer_chain *chain = buffer->first;
 	int n, i = 0;
 	if (howmuch < 0)
 		return -1;
 	ASSERT_EVBUFFER_LOCKED(buffer);
 	/* 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_WRITE_IOVEC && howmuch) {
 #ifdef USE_SENDFILE
 		/* we cannot write the file info via writev */
 		if (chain->flags & EVBUFFER_SENDFILE)
 			break;
 #endif
 		iov[i].IOV_PTR_FIELD = (void *) (chain->buffer + chain->misalign);
 		if ((size_t)howmuch >= chain->off) {
 			/* XXXcould be problematic when windows supports mmap*/
 			iov[i++].IOV_LEN_FIELD = (IOV_LEN_TYPE)chain->off;
 			howmuch -= chain->off;
 		} else {
 			/* XXXcould be problematic when windows supports mmap*/
 			iov[i++].IOV_LEN_FIELD = (IOV_LEN_TYPE)howmuch;
 			break;
 		}
 		chain = chain->next;
 	}
 	if (! i)
 		return 0;
 #ifdef WIN32
 	{
 		DWORD bytesSent;
 		if (WSASend(fd, iov, i, &bytesSent, 0, NULL, NULL))
 			n = -1;
 		else
 			n = bytesSent;
 	}
 #else
 	n = writev(fd, iov, i);
 #endif
 	return (n);
 }
 #endif
 #ifdef USE_SENDFILE
 static inline int
 evbuffer_write_sendfile(struct evbuffer *buffer, evutil_socket_t fd,
     ev_ssize_t howmuch)
 {
 	struct evbuffer_chain *chain = buffer->first;
 	struct evbuffer_chain_fd *info =
 	    EVBUFFER_CHAIN_EXTRA(struct evbuffer_chain_fd, chain);
 #if defined(SENDFILE_IS_MACOSX) || defined(SENDFILE_IS_FREEBSD)
 	int res;
 	off_t len = chain->off;
 #elif defined(SENDFILE_IS_LINUX) || defined(SENDFILE_IS_SOLARIS)
 	ev_ssize_t res;
 	off_t offset = chain->misalign;
 #endif
 	ASSERT_EVBUFFER_LOCKED(buffer);
 #if defined(SENDFILE_IS_MACOSX)
 	res = sendfile(info->fd, fd, chain->misalign, &len, NULL, 0);
 	if (res == -1 && !EVUTIL_ERR_RW_RETRIABLE(errno))
 		return (-1);
 	return (len);
 #elif defined(SENDFILE_IS_FREEBSD)
 	res = sendfile(info->fd, fd, chain->misalign, chain->off, NULL, &len, 0);
 	if (res == -1 && !EVUTIL_ERR_RW_RETRIABLE(errno))
 		return (-1);
 	return (len);
 #elif defined(SENDFILE_IS_LINUX)
 	/* TODO(niels): implement splice */
 	res = sendfile(fd, info->fd, &offset, chain->off);
 	if (res == -1 && EVUTIL_ERR_RW_RETRIABLE(errno)) {
 		/* if this is EAGAIN or EINTR return 0; otherwise, -1 */
 		return (0);
 	}
 	return (res);
 #elif defined(SENDFILE_IS_SOLARIS)
 	{
 		const off_t offset_orig = offset;
 		res = sendfile(fd, info->fd, &offset, chain->off);
 		if (res == -1 && EVUTIL_ERR_RW_RETRIABLE(errno)) {
 			if (offset - offset_orig)
 				return offset - offset_orig;
 			/* if this is EAGAIN or EINTR and no bytes were
 			 * written, return 0 */
 			return (0);
 		}
 		return (res);
 	}
 #endif
 }
 #endif
 int
 evbuffer_write_atmost(struct evbuffer *buffer, evutil_socket_t fd,
     ev_ssize_t howmuch)
 {
 	int n = -1;
 	EVBUFFER_LOCK(buffer);
 	if (buffer->freeze_start) {
 		goto done;
 	}
 	if (howmuch < 0 || (size_t)howmuch > buffer->total_len)
 		howmuch = buffer->total_len;
 	if (howmuch > 0) {
 #ifdef USE_SENDFILE
 		struct evbuffer_chain *chain = buffer->first;
 		if (chain != NULL && (chain->flags & EVBUFFER_SENDFILE))
 			n = evbuffer_write_sendfile(buffer, fd, howmuch);
 		else {
 #endif
 #ifdef USE_IOVEC_IMPL
 		n = evbuffer_write_iovec(buffer, fd, howmuch);
 #elif defined(WIN32)
 		/* XXX(nickm) Don't disable this code until we know if
 		 * the WSARecv code above works. */
 		void *p = evbuffer_pullup(buffer, howmuch);
 		n = send(fd, p, howmuch, 0);
 #else
 		void *p = evbuffer_pullup(buffer, howmuch);
 		n = write(fd, p, howmuch);
 #endif
 #ifdef USE_SENDFILE
 		}
 #endif
 	}
 	if (n > 0)
 		evbuffer_drain(buffer, n);
 done:
 	EVBUFFER_UNLOCK(buffer);
 	return (n);
 }
 int
 evbuffer_write(struct evbuffer *buffer, evutil_socket_t fd)
 {
 	return evbuffer_write_atmost(buffer, fd, -1);
 }
 unsigned char *
 evbuffer_find(struct evbuffer *buffer, const unsigned char *what, size_t len)
 {
 	unsigned char *search;
 	struct evbuffer_ptr ptr;
 	EVBUFFER_LOCK(buffer);
 	ptr = evbuffer_search(buffer, (const char *)what, len, NULL);
 	if (ptr.pos < 0) {
 		search = NULL;
 	} else {
 		search = evbuffer_pullup(buffer, ptr.pos + len);
 		if (search)
 			search += ptr.pos;
 	}
 	EVBUFFER_UNLOCK(buffer);
 	return search;
 }
 int
 evbuffer_ptr_set(struct evbuffer *buf, struct evbuffer_ptr *pos,
     size_t position, enum evbuffer_ptr_how how)
 {
 	size_t left = position;
 	struct evbuffer_chain *chain = NULL;
 	EVBUFFER_LOCK(buf);
 	switch (how) {
 	case EVBUFFER_PTR_SET:
 		chain = buf->first;
 		pos->pos = position;
 		position = 0;
 		break;
 	case EVBUFFER_PTR_ADD:
 		/* this avoids iterating over all previous chains if
 		   we just want to advance the position */
 		chain = pos->_internal.chain;
 		pos->pos += position;
 		position = pos->_internal.pos_in_chain;
 		break;
 	}
 	while (chain && position + left >= chain->off) {
 		left -= chain->off - position;
 		chain = chain->next;
 		position = 0;
 	}
 	if (chain) {
 		pos->_internal.chain = chain;
 		pos->_internal.pos_in_chain = position + left;
 	} else {
 		pos->_internal.chain = NULL;
 		pos->pos = -1;
 	}
 	EVBUFFER_UNLOCK(buf);
 	return chain != NULL ? 0 : -1;
 }
 /**
    Compare the bytes in buf at position pos to the len bytes in mem.  Return
    less than 0, 0, or greater than 0 as memcmp.
  */
 static int
 evbuffer_ptr_memcmp(const struct evbuffer *buf, const struct evbuffer_ptr *pos,
     const char *mem, size_t len)
 {
 	struct evbuffer_chain *chain;
 	size_t position;
 	int r;
 	ASSERT_EVBUFFER_LOCKED(buf);
 	if (pos->pos + len > buf->total_len)
 		return -1;
 	chain = pos->_internal.chain;
 	position = pos->_internal.pos_in_chain;
 	while (len && chain) {
 		size_t n_comparable;
 		if (len + position > chain->off)
 			n_comparable = chain->off - position;
 		else
 			n_comparable = len;
 		r = memcmp(chain->buffer + chain->misalign + position, mem,
 		    n_comparable);
 		if (r)
 			return r;
 		mem += n_comparable;
 		len -= n_comparable;
 		position = 0;
 		chain = chain->next;
 	}
 	return 0;
 }
 struct evbuffer_ptr
 evbuffer_search(struct evbuffer *buffer, const char *what, size_t len, const struct evbuffer_ptr *start)
 {
 	return evbuffer_search_range(buffer, what, len, start, NULL);
 }
 struct evbuffer_ptr
 evbuffer_search_range(struct evbuffer *buffer, const char *what, size_t len, const struct evbuffer_ptr *start, const struct evbuffer_ptr *end)
 {
 	struct evbuffer_ptr pos;
 	struct evbuffer_chain *chain, *last_chain = NULL;
 	const unsigned char *p;
 	char first;
 	EVBUFFER_LOCK(buffer);
 	if (start) {
 		memcpy(&pos, start, sizeof(pos));
 		chain = pos._internal.chain;
 	} else {
 		pos.pos = 0;
 		chain = pos._internal.chain = buffer->first;
 		pos._internal.pos_in_chain = 0;
 	}
 	if (end)
 		last_chain = end->_internal.chain;
 	if (!len || len > EV_SSIZE_MAX)
 		goto done;
 	first = what[0];
 	while (chain) {
 		const unsigned char *start_at =
 		    chain->buffer + chain->misalign +
 		    pos._internal.pos_in_chain;
 		p = memchr(start_at, first,
 		    chain->off - pos._internal.pos_in_chain);
 		if (p) {
 			pos.pos += p - start_at;
 			pos._internal.pos_in_chain += p - start_at;
 			if (!evbuffer_ptr_memcmp(buffer, &pos, what, len)) {
 				if (end && pos.pos + (ev_ssize_t)len > end->pos)
 					goto not_found;
 				else
 					goto done;
 			}
 			++pos.pos;
 			++pos._internal.pos_in_chain;
 			if (pos._internal.pos_in_chain == chain->off) {
 				chain = pos._internal.chain = chain->next;
 				pos._internal.pos_in_chain = 0;
 			}
 		} else {
 			if (chain == last_chain)
 				goto not_found;
 			pos.pos += chain->off - pos._internal.pos_in_chain;
 			chain = pos._internal.chain = chain->next;
 			pos._internal.pos_in_chain = 0;
 		}
 	}
 not_found:
 	pos.pos = -1;
 	pos._internal.chain = NULL;
 done:
 	EVBUFFER_UNLOCK(buffer);
 	return pos;
 }
 int
 evbuffer_peek(struct evbuffer *buffer, ev_ssize_t len,
     struct evbuffer_ptr *start_at,
     struct evbuffer_iovec *vec, int n_vec)
 {
 	struct evbuffer_chain *chain;
 	int idx = 0;
 	ev_ssize_t len_so_far = 0;
 	EVBUFFER_LOCK(buffer);
 	if (start_at) {
 		chain = start_at->_internal.chain;
 		len_so_far = chain->off
 		    - start_at->_internal.pos_in_chain;
 		idx = 1;
 		if (n_vec > 0) {
 			vec[0].iov_base = chain->buffer + chain->misalign
 			    + start_at->_internal.pos_in_chain;
 			vec[0].iov_len = len_so_far;
 		}
 		chain = chain->next;
 	} else {
 		chain = buffer->first;
 	}
 	if (n_vec == 0 && len < 0) {
 		/* If no vectors are provided and they asked for "everything",
 		 * pretend they asked for the actual available amount. */
 		len = buffer->total_len - len_so_far;
 	}
 	while (chain) {
 		if (len >= 0 && len_so_far >= len)
 			break;
 		if (idx<n_vec) {
 			vec[idx].iov_base = chain->buffer + chain->misalign;
 			vec[idx].iov_len = chain->off;
 		} else if (len<0) {
 			break;
 		}
 		++idx;
 		len_so_far += chain->off;
 		chain = chain->next;
 	}
 	EVBUFFER_UNLOCK(buffer);
 	return idx;
 }
 int
 evbuffer_add_vprintf(struct evbuffer *buf, const char *fmt, va_list ap)
 {
 	char *buffer;
 	size_t space;
 	int sz, result = -1;
 	va_list aq;
 	struct evbuffer_chain *chain;
 	EVBUFFER_LOCK(buf);
 	if (buf->freeze_end) {
 		goto done;
 	}
 	/* make sure that at least some space is available */
 	if ((chain = evbuffer_expand_singlechain(buf, 64)) == NULL)
 		goto done;
 	for (;;) {
 #if 0
 		size_t used = chain->misalign + chain->off;
 		buffer = (char *)chain->buffer + chain->misalign + chain->off;
 		EVUTIL_ASSERT(chain->buffer_len >= used);
 		space = chain->buffer_len - used;
 #endif
 		buffer = (char*) CHAIN_SPACE_PTR(chain);
 		space = (size_t) CHAIN_SPACE_LEN(chain);
 #ifndef va_copy
 #define	va_copy(dst, src)	memcpy(&(dst), &(src), sizeof(va_list))
 #endif
 		va_copy(aq, ap);
 		sz = evutil_vsnprintf(buffer, space, fmt, aq);
 		va_end(aq);
 		if (sz < 0)
 			goto done;
 		if ((size_t)sz < space) {
 			chain->off += sz;
 			buf->total_len += sz;
 			buf->n_add_for_cb += sz;
 			advance_last_with_data(buf);
 			evbuffer_invoke_callbacks(buf);
 			result = sz;
 			goto done;
 		}
 		if ((chain = evbuffer_expand_singlechain(buf, sz + 1)) == NULL)
 			goto done;
 	}
 	/* NOTREACHED */
 done:
 	EVBUFFER_UNLOCK(buf);
 	return result;
 }
 int
 evbuffer_add_printf(struct evbuffer *buf, const char *fmt, ...)
 {
 	int res = -1;
 	va_list ap;
 	va_start(ap, fmt);
 	res = evbuffer_add_vprintf(buf, fmt, ap);
 	va_end(ap);
 	return (res);
 }
 int
 evbuffer_add_reference(struct evbuffer *outbuf,
     const void *data, size_t datlen,
     evbuffer_ref_cleanup_cb cleanupfn, void *extra)
 {
 	struct evbuffer_chain *chain;
 	struct evbuffer_chain_reference *info;
 	int result = -1;
 	chain = evbuffer_chain_new(sizeof(struct evbuffer_chain_reference));
 	if (!chain)
 		return (-1);
 	chain->flags |= EVBUFFER_REFERENCE | EVBUFFER_IMMUTABLE;
 	chain->buffer = (u_char *)data;
 	chain->buffer_len = datlen;
 	chain->off = datlen;
 	info = EVBUFFER_CHAIN_EXTRA(struct evbuffer_chain_reference, chain);
 	info->cleanupfn = cleanupfn;
 	info->extra = extra;
 	EVBUFFER_LOCK(outbuf);
 	if (outbuf->freeze_end) {
 		/* don't call chain_free; we do not want to actually invoke
 		 * the cleanup function */
 		mm_free(chain);
 		goto done;
 	}
 	evbuffer_chain_insert(outbuf, chain);
 	outbuf->n_add_for_cb += datlen;
 	evbuffer_invoke_callbacks(outbuf);
 	result = 0;
 done:
 	EVBUFFER_UNLOCK(outbuf);
 	return result;
 }
 /* TODO(niels): maybe we don't want to own the fd, however, in that
  * case, we should dup it - dup is cheap.  Perhaps, we should use a
  * callback instead?
  */
 /* TODO(niels): we may want to add to automagically convert to mmap, in
  * case evbuffer_remove() or evbuffer_pullup() are being used.
  */
 int
 evbuffer_add_file(struct evbuffer *outbuf, int fd,
     ev_off_t offset, ev_off_t length)
 {
 #if defined(USE_SENDFILE) || defined(_EVENT_HAVE_MMAP)
 	struct evbuffer_chain *chain;
 	struct evbuffer_chain_fd *info;
 #endif
 #if defined(USE_SENDFILE)
 	int sendfile_okay = 1;
 #endif
 	int ok = 1;
 #if defined(USE_SENDFILE)
 	if (use_sendfile) {
 		EVBUFFER_LOCK(outbuf);
 		sendfile_okay = outbuf->flags & EVBUFFER_FLAG_DRAINS_TO_FD;
 		EVBUFFER_UNLOCK(outbuf);
 	}
 	if (use_sendfile && sendfile_okay) {
 		chain = evbuffer_chain_new(sizeof(struct evbuffer_chain_fd));
 		if (chain == NULL) {
 			event_warn("%s: out of memory", __func__);
 			return (-1);
 		}
 		chain->flags |= EVBUFFER_SENDFILE | EVBUFFER_IMMUTABLE;
 		chain->buffer = NULL;	/* no reading possible */
 		chain->buffer_len = length + offset;
 		chain->off = length;
 		chain->misalign = offset;
 		info = EVBUFFER_CHAIN_EXTRA(struct evbuffer_chain_fd, chain);
 		info->fd = fd;
 		EVBUFFER_LOCK(outbuf);
 		if (outbuf->freeze_end) {
 			mm_free(chain);
 			ok = 0;
 		} else {
 			outbuf->n_add_for_cb += length;
 			evbuffer_chain_insert(outbuf, chain);
 		}
 	} else
 #endif
 #if defined(_EVENT_HAVE_MMAP)
 	if (use_mmap) {
 		void *mapped = mmap(NULL, length + offset, PROT_READ,
 #ifdef MAP_NOCACHE
 		    MAP_NOCACHE |
 #endif
 #ifdef MAP_FILE
 		    MAP_FILE |
 #endif
 		    MAP_PRIVATE,
 		    fd, 0);
 		/* some mmap implementations require offset to be a multiple of
 		 * the page size.  most users of this api, are likely to use 0
 		 * so mapping everything is not likely to be a problem.
 		 * TODO(niels): determine page size and round offset to that
 		 * page size to avoid mapping too much memory.
 		 */
 		if (mapped == MAP_FAILED) {
 			event_warn("%s: mmap(%d, %d, %zu) failed",
 			    __func__, fd, 0, (size_t)(offset + length));
 			return (-1);
 		}
 		chain = evbuffer_chain_new(sizeof(struct evbuffer_chain_fd));
 		if (chain == NULL) {
 			event_warn("%s: out of memory", __func__);
 			munmap(mapped, length);
 			return (-1);
 		}
 		chain->flags |= EVBUFFER_MMAP | EVBUFFER_IMMUTABLE;
 		chain->buffer = mapped;
 		chain->buffer_len = length + offset;
 		chain->off = length + offset;
 		info = EVBUFFER_CHAIN_EXTRA(struct evbuffer_chain_fd, chain);
 		info->fd = fd;
 		EVBUFFER_LOCK(outbuf);
 		if (outbuf->freeze_end) {
 			info->fd = -1;
 			evbuffer_chain_free(chain);
 			ok = 0;
 		} else {
 			outbuf->n_add_for_cb += length;
 			evbuffer_chain_insert(outbuf, chain);
 			/* we need to subtract whatever we don't need */
 			evbuffer_drain(outbuf, offset);
 		}
 	} else
 #endif
 	{
 		/* the default implementation */
 		struct evbuffer *tmp = evbuffer_new();
 		ev_ssize_t read;
 		if (tmp == NULL)
 			return (-1);
 #ifdef WIN32
 #define lseek _lseeki64
 #endif
 		if (lseek(fd, offset, SEEK_SET) == -1) {
 			evbuffer_free(tmp);
 			return (-1);
 		}
 		/* we add everything to a temporary buffer, so that we
 		 * can abort without side effects if the read fails.
 		 */
 		while (length) {
 			read = evbuffer_readfile(tmp, fd, (ev_ssize_t)length);
 			if (read == -1) {
 				evbuffer_free(tmp);
 				return (-1);
 			}
 			length -= read;
 		}
 		EVBUFFER_LOCK(outbuf);
 		if (outbuf->freeze_end) {
 			evbuffer_free(tmp);
 			ok = 0;
 		} else {
 			evbuffer_add_buffer(outbuf, tmp);
 			evbuffer_free(tmp);
 #ifdef WIN32
 #define close _close
 #endif
 			close(fd);
 		}
 	}
 	if (ok)
 		evbuffer_invoke_callbacks(outbuf);
 	EVBUFFER_UNLOCK(outbuf);
 	return ok ? 0 : -1;
 }
 void
 evbuffer_setcb(struct evbuffer *buffer, evbuffer_cb cb, void *cbarg)
 {
 	EVBUFFER_LOCK(buffer);
 	if (!TAILQ_EMPTY(&buffer->callbacks))
 		evbuffer_remove_all_callbacks(buffer);
 	if (cb) {
 		struct evbuffer_cb_entry *ent =
 		    evbuffer_add_cb(buffer, NULL, cbarg);
 		ent->cb.cb_obsolete = cb;
 		ent->flags |= EVBUFFER_CB_OBSOLETE;
 	}
 	EVBUFFER_UNLOCK(buffer);
 }
 struct evbuffer_cb_entry *
 evbuffer_add_cb(struct evbuffer *buffer, evbuffer_cb_func cb, void *cbarg)
 {
 	struct evbuffer_cb_entry *e;
 	if (! (e = mm_calloc(1, sizeof(struct evbuffer_cb_entry))))
 		return NULL;
 	EVBUFFER_LOCK(buffer);
 	e->cb.cb_func = cb;
 	e->cbarg = cbarg;
 	e->flags = EVBUFFER_CB_ENABLED;
 	TAILQ_INSERT_HEAD(&buffer->callbacks, e, next);
 	EVBUFFER_UNLOCK(buffer);
 	return e;
 }
 int
 evbuffer_remove_cb_entry(struct evbuffer *buffer,
 			 struct evbuffer_cb_entry *ent)
 {
 	EVBUFFER_LOCK(buffer);
 	TAILQ_REMOVE(&buffer->callbacks, ent, next);
 	EVBUFFER_UNLOCK(buffer);
 	mm_free(ent);
 	return 0;
 }
 int
 evbuffer_remove_cb(struct evbuffer *buffer, evbuffer_cb_func cb, void *cbarg)
 {
 	struct evbuffer_cb_entry *cbent;
 	int result = -1;
 	EVBUFFER_LOCK(buffer);
 	TAILQ_FOREACH(cbent, &buffer->callbacks, next) {
 		if (cb == cbent->cb.cb_func && cbarg == cbent->cbarg) {
 			result = evbuffer_remove_cb_entry(buffer, cbent);
 			goto done;
 		}
 	}
 done:
 	EVBUFFER_UNLOCK(buffer);
 	return result;
 }
 int
 evbuffer_cb_set_flags(struct evbuffer *buffer,
 		      struct evbuffer_cb_entry *cb, ev_uint32_t flags)
 {
 	/* the user isn't allowed to mess with these. */
 	flags &= ~EVBUFFER_CB_INTERNAL_FLAGS;
 	EVBUFFER_LOCK(buffer);
 	cb->flags |= flags;
 	EVBUFFER_UNLOCK(buffer);
 	return 0;
 }
 int
 evbuffer_cb_clear_flags(struct evbuffer *buffer,
 		      struct evbuffer_cb_entry *cb, ev_uint32_t flags)
 {
 	/* the user isn't allowed to mess with these. */
 	flags &= ~EVBUFFER_CB_INTERNAL_FLAGS;
 	EVBUFFER_LOCK(buffer);
 	cb->flags &= ~flags;
 	EVBUFFER_UNLOCK(buffer);
 	return 0;
 }
 int
 evbuffer_freeze(struct evbuffer *buffer, int start)
 {
 	EVBUFFER_LOCK(buffer);
 	if (start)
 		buffer->freeze_start = 1;
 	else
 		buffer->freeze_end = 1;
 	EVBUFFER_UNLOCK(buffer);
 	return 0;
 }
 int
 evbuffer_unfreeze(struct evbuffer *buffer, int start)
 {
 	EVBUFFER_LOCK(buffer);
 	if (start)
 		buffer->freeze_start = 0;
 	else
 		buffer->freeze_end = 0;
 	EVBUFFER_UNLOCK(buffer);
 	return 0;
 }
 #if 0
 void
 evbuffer_cb_suspend(struct evbuffer *buffer, struct evbuffer_cb_entry *cb)
 {
 	if (!(cb->flags & EVBUFFER_CB_SUSPENDED)) {
 		cb->size_before_suspend = evbuffer_get_length(buffer);
 		cb->flags |= EVBUFFER_CB_SUSPENDED;
 	}
 }
 void
 evbuffer_cb_unsuspend(struct evbuffer *buffer, struct evbuffer_cb_entry *cb)
 {
 	if ((cb->flags & EVBUFFER_CB_SUSPENDED)) {
 		unsigned call = (cb->flags & EVBUFFER_CB_CALL_ON_UNSUSPEND);
 		size_t sz = cb->size_before_suspend;
 		cb->flags &= ~(EVBUFFER_CB_SUSPENDED|
 			       EVBUFFER_CB_CALL_ON_UNSUSPEND);
 		cb->size_before_suspend = 0;
 		if (call && (cb->flags & EVBUFFER_CB_ENABLED)) {
 			cb->cb(buffer, sz, evbuffer_get_length(buffer), cb->cbarg);
 		}
 	}
 }
 #endif
 /* These hooks are exposed so that the unit tests can temporarily disable
  * sendfile support in order to test mmap, or both to test linear
  * access. Don't use it; if we need to add a way to disable sendfile support
  * in the future, it will probably be via an alternate version of
  * evbuffer_add_file() with a 'flags' argument.
  */
 int _evbuffer_testing_use_sendfile(void);
 int _evbuffer_testing_use_mmap(void);
 int _evbuffer_testing_use_linear_file_access(void);
 int
 _evbuffer_testing_use_sendfile(void)
 {
 	int ok = 0;
 #ifdef USE_SENDFILE
 	use_sendfile = 1;
 	ok = 1;
 #endif
 #ifdef _EVENT_HAVE_MMAP
 	use_mmap = 0;
 #endif
 	return ok;
 }
 int
 _evbuffer_testing_use_mmap(void)
 {
 	int ok = 0;
 #ifdef USE_SENDFILE
 	use_sendfile = 0;
 #endif
 #ifdef _EVENT_HAVE_MMAP
 	use_mmap = 1;
 	ok = 1;
 #endif
 	return ok;
 }
 int
 _evbuffer_testing_use_linear_file_access(void)
 {
 #ifdef USE_SENDFILE
 	use_sendfile = 0;
 #endif
 #ifdef _EVENT_HAVE_MMAP
 	use_mmap = 0;
 #endif
 	return 1;
 }

The Tor Browser / annotate

ipc/chromium/src/third_party/libevent/buffer.c@6474c204b198 (annotated)

ipc/chromium/src/third_party/libevent/buffer.c