Adding upstream version 1.0.18.upstream/1.0.18upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 3467 insertions, 0 deletions

diff --git a/libevent/buffer.c b/libevent/buffer.c
new file mode 100644
index 0000000..3524b35
--- /dev/null
+++ b/libevent/buffer.c
@@ -0,0 +1,3467 @@
+/*
+ * 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"
+#include "evconfig-private.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 _GNU_SOURCE before we include
+ * stdio.h.  This comes from evconfig-private.h.
+ */
+#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
+#ifdef EVENT__HAVE_SYS_STAT_H
+#include <sys/stat.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 "log-internal.h"
+#include "mm-internal.h"
+#include "util-internal.h"
+#include "evthread-internal.h"
+#include "evbuffer-internal.h"
+#include "bufferevent-internal.h"
+#include "event-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
+
+/* 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 ? \
+	    0 : (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)
+
+/* evbuffer_ptr support */
+#define PTR_NOT_FOUND(ptr) do {			\
+	(ptr)->pos = -1;					\
+	(ptr)->internal_.chain = NULL;		\
+	(ptr)->internal_.pos_in_chain = 0;	\
+} while (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 event_callback *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);
+static int evbuffer_ptr_subtract(struct evbuffer *buf, struct evbuffer_ptr *pos,
+    size_t howfar);
+static int evbuffer_file_segment_materialize(struct evbuffer_file_segment *seg);
+static inline void evbuffer_chain_incref(struct evbuffer_chain *chain);
+
+static struct evbuffer_chain *
+evbuffer_chain_new(size_t size)
+{
+	struct evbuffer_chain *chain;
+	size_t to_alloc;
+
+	if (size > EVBUFFER_CHAIN_MAX - EVBUFFER_CHAIN_SIZE)
+		return (NULL);
+
+	size += EVBUFFER_CHAIN_SIZE;
+
+	/* get the next largest memory that can hold the buffer */
+	if (size < EVBUFFER_CHAIN_MAX / 2) {
+		to_alloc = MIN_BUFFER_SIZE;
+		while (to_alloc < size) {
+			to_alloc <<= 1;
+		}
+	} else {
+		to_alloc = size;
+	}
+
+	/* 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(unsigned char, chain);
+
+	chain->refcnt = 1;
+
+	return (chain);
+}
+
+static inline void
+evbuffer_chain_free(struct evbuffer_chain *chain)
+{
+	EVUTIL_ASSERT(chain->refcnt > 0);
+	if (--chain->refcnt > 0) {
+		/* chain is still referenced by other chains */
+		return;
+	}
+
+	if (CHAIN_PINNED(chain)) {
+		/* will get freed once no longer dangling */
+		chain->refcnt++;
+		chain->flags |= EVBUFFER_DANGLING;
+		return;
+	}
+
+	/* safe to release chain, it's either a referencing
+	 * chain or all references to it have been freed */
+	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);
+	}
+	if (chain->flags & EVBUFFER_FILESEGMENT) {
+		struct evbuffer_chain_file_segment *info =
+		    EVBUFFER_CHAIN_EXTRA(
+			    struct evbuffer_chain_file_segment,
+			    chain);
+		if (info->segment) {
+#ifdef _WIN32
+			if (info->segment->is_mapping)
+				UnmapViewOfFile(chain->buffer);
+#endif
+			evbuffer_file_segment_free(info->segment);
+		}
+	}
+	if (chain->flags & EVBUFFER_MULTICAST) {
+		struct evbuffer_multicast_parent *info =
+		    EVBUFFER_CHAIN_EXTRA(
+			    struct evbuffer_multicast_parent,
+			    chain);
+		/* referencing chain is being freed, decrease
+		 * refcounts of source chain and associated
+		 * evbuffer (which get freed once both reach
+		 * zero) */
+		EVUTIL_ASSERT(info->source != NULL);
+		EVUTIL_ASSERT(info->parent != NULL);
+		EVBUFFER_LOCK(info->source);
+		evbuffer_chain_free(info->parent);
+		evbuffer_decref_and_unlock_(info->source);
+	}
+
+	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 **chp;
+		chp = evbuffer_free_trailing_empty_chains(buf);
+		*chp = chain;
+		if (chain->off)
+			buf->last_with_datap = chp;
+		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);
+}
+
+static inline void
+evbuffer_chain_incref(struct evbuffer_chain *chain)
+{
+    ++chain->refcnt;
+}
+
+struct evbuffer *
+evbuffer_new(void)
+{
+	struct evbuffer *buffer;
+
+	buffer = mm_calloc(1, sizeof(struct evbuffer));
+	if (buffer == NULL)
+		return (NULL);
+
+	LIST_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 = base;
+	buffer->deferred_cbs = 1;
+	event_deferred_cb_init_(&buffer->deferred,
+	    event_base_get_npriorities(base) / 2,
+	    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 (LIST_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 = LIST_FIRST(&buffer->callbacks);
+	     cbent != LIST_END(&buffer->callbacks);
+	     cbent = next) {
+		/* Get the 'next' pointer now in case this callback decides
+		 * to remove itself or something. */
+		next = LIST_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 (LIST_EMPTY(&buffer->callbacks)) {
+		buffer->n_add_for_cb = buffer->n_del_for_cb = 0;
+		return;
+	}
+
+	if (buffer->deferred_cbs) {
+		if (event_deferred_cb_schedule_(buffer->cb_queue, &buffer->deferred)) {
+			evbuffer_incref_and_lock_(buffer);
+			if (buffer->parent)
+				bufferevent_incref_(buffer->parent);
+			EVBUFFER_UNLOCK(buffer);
+		}
+	}
+
+	evbuffer_run_callbacks(buffer, 0);
+}
+
+static void
+evbuffer_deferred_callback(struct event_callback *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 = LIST_FIRST(&buffer->callbacks))) {
+		LIST_REMOVE(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;
+}
+
+size_t
+evbuffer_add_iovec(struct evbuffer * buf, struct evbuffer_iovec * vec, int n_vec) {
+	int n;
+	size_t res;
+	size_t to_alloc;
+
+	EVBUFFER_LOCK(buf);
+
+	res = to_alloc = 0;
+
+	for (n = 0; n < n_vec; n++) {
+		to_alloc += vec[n].iov_len;
+	}
+
+	if (evbuffer_expand_fast_(buf, to_alloc, 2) < 0) {
+		goto done;
+	}
+
+	for (n = 0; n < n_vec; n++) {
+		/* XXX each 'add' call here does a bunch of setup that's
+		 * obviated by evbuffer_expand_fast_, and some cleanup that we
+		 * would like to do only once.  Instead we should just extract
+		 * the part of the code that's needed. */
+
+		if (evbuffer_add(buf, vec[n].iov_base, vec[n].iov_len) < 0) {
+			goto done;
+		}
+
+		res += vec[n].iov_len;
+	}
+
+done:
+    EVBUFFER_UNLOCK(buf);
+    return res;
+}
+
+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 = (void *)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;
+	struct evbuffer_chain **chainp = buf->last_with_datap;
+
+	ASSERT_EVBUFFER_LOCKED(buf);
+
+	if (!*chainp)
+		return 0;
+
+	while ((*chainp)->next) {
+		chainp = &(*chainp)->next;
+		if ((*chainp)->off)
+			buf->last_with_datap = chainp;
+		++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)
+{
+	struct evbuffer_chain **chp;
+
+	ASSERT_EVBUFFER_LOCKED(dst);
+	ASSERT_EVBUFFER_LOCKED(src);
+
+	chp = evbuffer_free_trailing_empty_chains(dst);
+	*chp = src->first;
+
+	if (src->last_with_datap == &src->first)
+		dst->last_with_datap = chp;
+	else
+		dst->last_with_datap = src->last_with_datap;
+	dst->last = src->last;
+	dst->total_len += src->total_len;
+}
+
+static inline void
+APPEND_CHAIN_MULTICAST(struct evbuffer *dst, struct evbuffer *src)
+{
+	struct evbuffer_chain *tmp;
+	struct evbuffer_chain *chain = src->first;
+	struct evbuffer_multicast_parent *extra;
+
+	ASSERT_EVBUFFER_LOCKED(dst);
+	ASSERT_EVBUFFER_LOCKED(src);
+
+	for (; chain; chain = chain->next) {
+		if (!chain->off || chain->flags & EVBUFFER_DANGLING) {
+			/* skip empty chains */
+			continue;
+		}
+
+		tmp = evbuffer_chain_new(sizeof(struct evbuffer_multicast_parent));
+		if (!tmp) {
+			event_warn("%s: out of memory", __func__);
+			return;
+		}
+		extra = EVBUFFER_CHAIN_EXTRA(struct evbuffer_multicast_parent, tmp);
+		/* reference evbuffer containing source chain so it
+		 * doesn't get released while the chain is still
+		 * being referenced to */
+		evbuffer_incref_(src);
+		extra->source = src;
+		/* reference source chain which now becomes immutable */
+		evbuffer_chain_incref(chain);
+		extra->parent = chain;
+		chain->flags |= EVBUFFER_IMMUTABLE;
+		tmp->buffer_len = chain->buffer_len;
+		tmp->misalign = chain->misalign;
+		tmp->off = chain->off;
+		tmp->flags |= EVBUFFER_MULTICAST|EVBUFFER_IMMUTABLE;
+		tmp->buffer = chain->buffer;
+		evbuffer_chain_insert(dst, tmp);
+	}
+}
+
+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_add_buffer_reference(struct evbuffer *outbuf, struct evbuffer *inbuf)
+{
+	size_t in_total_len, out_total_len;
+	struct evbuffer_chain *chain;
+	int result = 0;
+
+	EVBUFFER_LOCK2(inbuf, outbuf);
+	in_total_len = inbuf->total_len;
+	out_total_len = outbuf->total_len;
+	chain = inbuf->first;
+
+	if (in_total_len == 0)
+		goto done;
+
+	if (outbuf->freeze_end || outbuf == inbuf) {
+		result = -1;
+		goto done;
+	}
+
+	for (; chain; chain = chain->next) {
+		if ((chain->flags & (EVBUFFER_FILESEGMENT|EVBUFFER_SENDFILE|EVBUFFER_MULTICAST)) != 0) {
+			/* chain type can not be referenced */
+			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);
+	}
+	APPEND_CHAIN_MULTICAST(outbuf, inbuf);
+
+	outbuf->n_add_for_cb += in_total_len;
+	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;
+		EVUTIL_ASSERT(remaining <= chain->off);
+		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_from(buf, NULL, 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)
+{
+	return evbuffer_copyout_from(buf, NULL, data_out, datlen);
+}
+
+ev_ssize_t
+evbuffer_copyout_from(struct evbuffer *buf, const struct evbuffer_ptr *pos,
+    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;
+	size_t pos_in_chain;
+
+	EVBUFFER_LOCK(buf);
+
+	if (pos) {
+		if (datlen > (size_t)(EV_SSIZE_MAX - pos->pos)) {
+			result = -1;
+			goto done;
+		}
+		chain = pos->internal_.chain;
+		pos_in_chain = pos->internal_.pos_in_chain;
+		if (datlen + pos->pos > buf->total_len)
+			datlen = buf->total_len - pos->pos;
+	} else {
+		chain = buf->first;
+		pos_in_chain = 0;
+		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 - pos_in_chain) {
+		size_t copylen = chain->off - pos_in_chain;
+		memcpy(data,
+		    chain->buffer + chain->misalign + pos_in_chain,
+		    copylen);
+		data += copylen;
+		datlen -= copylen;
+
+		chain = chain->next;
+		pos_in_chain = 0;
+		EVUTIL_ASSERT(chain || datlen==0);
+	}
+
+	if (datlen) {
+		EVUTIL_ASSERT(chain);
+		EVUTIL_ASSERT(datlen+pos_in_chain <= chain->off);
+
+		memcpy(data, chain->buffer + chain->misalign + pos_in_chain,
+		    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 (chain != src->first) {
+		/* 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;
+
+		if (chain->buffer) {
+			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 size_t
+evbuffer_strspn(
+	struct evbuffer_ptr *ptr, const char *chrset)
+{
+	size_t count = 0;
+	struct evbuffer_chain *chain = ptr->internal_.chain;
+	size_t i = ptr->internal_.pos_in_chain;
+
+	if (!chain)
+		return 0;
+
+	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 int
+evbuffer_getchr(struct evbuffer_ptr *it)
+{
+	struct evbuffer_chain *chain = it->internal_.chain;
+	size_t off = it->internal_.pos_in_chain;
+
+	if (chain == NULL)
+		return -1;
+
+	return (unsigned char)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;
+
+	/* Avoid locking in trivial edge cases */
+	if (start && start->internal_.chain == NULL) {
+		PTR_NOT_FOUND(&it);
+		if (eol_len_out)
+			*eol_len_out = extra_drain;
+		return it;
+	}
+
+	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: {
+		ev_ssize_t start_pos = it.pos;
+		/* Look for a LF ... */
+		if (evbuffer_strchr(&it, '\n') < 0)
+			goto done;
+		extra_drain = 1;
+		/* ... optionally preceeded by a CR. */
+		if (it.pos == start_pos)
+			break; /* If the first character is \n, don't back up */
+		/* This potentially does an extra linear walk over the first
+		 * few chains.  Probably, that's not too expensive unless you
+		 * have a really pathological setup. */
+		memcpy(&it2, &it, sizeof(it));
+		if (evbuffer_ptr_subtract(buffer, &it2, 1)<0)
+			break;
+		if (evbuffer_getchr(&it2) == '\r') {
+			memcpy(&it, &it2, sizeof(it));
+			extra_drain = 2;
+		}
+		break;
+	}
+	case EVBUFFER_EOL_LF:
+		if (evbuffer_strchr(&it, '\n') < 0)
+			goto done;
+		extra_drain = 1;
+		break;
+	case EVBUFFER_EOL_NUL:
+		if (evbuffer_strchr(&it, '\0') < 0)
+			goto done;
+		extra_drain = 1;
+		break;
+	default:
+		goto done;
+	}
+
+	ok = 1;
+done:
+	EVBUFFER_UNLOCK(buffer);
+
+	if (!ok)
+		PTR_NOT_FOUND(&it);
+	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;
+	}
+	/* Prevent buf->total_len overflow */
+	if (datlen > EV_SIZE_MAX - buf->total_len) {
+		goto done;
+	}
+
+	if (*buf->last_with_datap == NULL) {
+		chain = buf->last;
+	} else {
+		chain = *buf->last_with_datap;
+	}
+
+	/* 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) {
+		/* Always true for mutable buffers */
+		EVUTIL_ASSERT(chain->misalign >= 0 &&
+		    (ev_uint64_t)chain->misalign <= EVBUFFER_CHAIN_MAX);
+		remain = chain->buffer_len - (size_t)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 (datlen == 0) {
+		result = 0;
+		goto done;
+	}
+	if (buf->freeze_start) {
+		goto done;
+	}
+	if (datlen > EV_SIZE_MAX - buf->total_len) {
+		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) {
+		/* Always true for mutable buffers */
+		EVUTIL_ASSERT(chain->misalign >= 0 &&
+		    (ev_uint64_t)chain->misalign <= EVBUFFER_CHAIN_MAX);
+
+		/* 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 && chain->off)
+		buf->last_with_datap = &tmp->next;
+
+	tmp->next = chain;
+
+	tmp->off = datlen;
+	EVUTIL_ASSERT(datlen <= tmp->buffer_len);
+	tmp->misalign = tmp->buffer_len - datlen;
+
+	memcpy(tmp->buffer + tmp->misalign, data, datlen);
+	buf->total_len += datlen;
+	buf->n_add_for_cb += datlen;
+
+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 ||
+		datlen >= (EVBUFFER_CHAIN_MAX - chain->off)) {
+		/* 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 {
+			/* can't overflow, since only mutable chains have
+			 * huge misaligns. */
+			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);
+		}
+		EVUTIL_ASSERT(datlen >= avail);
+		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;
+	EVUTIL_ASSERT(*firstchainp);
+	if (CHAIN_SPACE_LEN(*firstchainp) == 0) {
+		firstchainp = &(*firstchainp)->next;
+	}
+
+	chain = *firstchainp;
+	EVUTIL_ASSERT(chain);
+	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 = (void *)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;
+	/* Can overflow, but mostly harmlessly. XXXX */
+	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) {
+		/* can't overflow, since only mutable chains have
+		 * huge misaligns. */
+		size_t space = (size_t) CHAIN_SPACE_LEN(*chainp);
+		/* XXXX This is a kludge that can waste space in perverse
+		 * situations. */
+		if (space > EVBUFFER_CHAIN_MAX)
+			space = EVBUFFER_CHAIN_MAX;
+		if ((ev_ssize_t)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 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 dest_fd,
+    ev_ssize_t howmuch)
+{
+	struct evbuffer_chain *chain = buffer->first;
+	struct evbuffer_chain_file_segment *info =
+	    EVBUFFER_CHAIN_EXTRA(struct evbuffer_chain_file_segment,
+		chain);
+	const int source_fd = info->segment->fd;
+#if defined(SENDFILE_IS_MACOSX) || defined(SENDFILE_IS_FREEBSD)
+	int res;
+	ev_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(source_fd, dest_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(source_fd, dest_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(dest_fd, source_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(dest_fd, source_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);
+		EVUTIL_ASSERT(p || !howmuch);
+		n = send(fd, p, howmuch, 0);
+#else
+		void *p = evbuffer_pullup(buffer, howmuch);
+		EVUTIL_ASSERT(p || !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;
+}
+
+/* Subract <b>howfar</b> from the position of <b>pos</b> within
+ * <b>buf</b>. Returns 0 on success, -1 on failure.
+ *
+ * This isn't exposed yet, because of potential inefficiency issues.
+ * Maybe it should be. */
+static int
+evbuffer_ptr_subtract(struct evbuffer *buf, struct evbuffer_ptr *pos,
+    size_t howfar)
+{
+	if (pos->pos < 0)
+		return -1;
+	if (howfar > (size_t)pos->pos)
+		return -1;
+	if (pos->internal_.chain && howfar <= pos->internal_.pos_in_chain) {
+		pos->internal_.pos_in_chain -= howfar;
+		pos->pos -= howfar;
+		return 0;
+	} else {
+		const size_t newpos = pos->pos - howfar;
+		/* Here's the inefficient part: it walks over the
+		 * chains until we hit newpos. */
+		return evbuffer_ptr_set(buf, pos, newpos, EVBUFFER_PTR_SET);
+	}
+}
+
+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;
+	int result = 0;
+
+	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 */
+		if (pos->pos < 0 || EV_SIZE_MAX - position < (size_t)pos->pos) {
+			EVBUFFER_UNLOCK(buf);
+			return -1;
+		}
+		chain = pos->internal_.chain;
+		pos->pos += position;
+		position = pos->internal_.pos_in_chain;
+		break;
+	}
+
+	EVUTIL_ASSERT(EV_SIZE_MAX - left >= position);
+	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 if (left == 0) {
+		/* The first byte in the (nonexistent) chain after the last chain */
+		pos->internal_.chain = NULL;
+		pos->internal_.pos_in_chain = 0;
+	} else {
+		PTR_NOT_FOUND(pos);
+		result = -1;
+	}
+
+	EVBUFFER_UNLOCK(buf);
+
+	return result;
+}
+
+/**
+   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 < 0 ||
+	    EV_SIZE_MAX - len < (size_t)pos->pos ||
+	    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:
+	PTR_NOT_FOUND(&pos);
+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;
+
+	/* Avoid locking in trivial edge cases */
+	if (start_at && start_at->internal_.chain == NULL)
+		return 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 = (void *)(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;
+		if (start_at) {
+			len -= start_at->pos;
+		}
+	}
+
+	while (chain) {
+		if (len >= 0 && len_so_far >= len)
+			break;
+		if (idx<n_vec) {
+			vec[idx].iov_base = (void *)(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 (INT_MAX >= EVBUFFER_CHAIN_MAX &&
+		    (size_t)sz >= EVBUFFER_CHAIN_MAX)
+			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 = (unsigned 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): we may want to add to automagically convert to mmap, in
+ * case evbuffer_remove() or evbuffer_pullup() are being used.
+ */
+struct evbuffer_file_segment *
+evbuffer_file_segment_new(
+	int fd, ev_off_t offset, ev_off_t length, unsigned flags)
+{
+	struct evbuffer_file_segment *seg =
+	    mm_calloc(sizeof(struct evbuffer_file_segment), 1);
+	if (!seg)
+		return NULL;
+	seg->refcnt = 1;
+	seg->fd = fd;
+	seg->flags = flags;
+	seg->file_offset = offset;
+	seg->cleanup_cb = NULL;
+	seg->cleanup_cb_arg = NULL;
+#ifdef _WIN32
+#ifndef lseek
+#define lseek _lseeki64
+#endif
+#ifndef fstat
+#define fstat _fstat
+#endif
+#ifndef stat
+#define stat _stat
+#endif
+#endif
+	if (length == -1) {
+		struct stat st;
+		if (fstat(fd, &st) < 0)
+			goto err;
+		length = st.st_size;
+	}
+	seg->length = length;
+
+	if (offset < 0 || length < 0 ||
+	    ((ev_uint64_t)length > EVBUFFER_CHAIN_MAX) ||
+	    (ev_uint64_t)offset > (ev_uint64_t)(EVBUFFER_CHAIN_MAX - length))
+		goto err;
+
+#if defined(USE_SENDFILE)
+	if (!(flags & EVBUF_FS_DISABLE_SENDFILE)) {
+		seg->can_sendfile = 1;
+		goto done;
+	}
+#endif
+
+	if (evbuffer_file_segment_materialize(seg)<0)
+		goto err;
+
+#if defined(USE_SENDFILE)
+done:
+#endif
+	if (!(flags & EVBUF_FS_DISABLE_LOCKING)) {
+		EVTHREAD_ALLOC_LOCK(seg->lock, 0);
+	}
+	return seg;
+err:
+	mm_free(seg);
+	return NULL;
+}
+
+#ifdef EVENT__HAVE_MMAP
+static long
+get_page_size(void)
+{
+#ifdef SC_PAGE_SIZE
+	return sysconf(SC_PAGE_SIZE);
+#elif defined(_SC_PAGE_SIZE)
+	return sysconf(_SC_PAGE_SIZE);
+#else
+	return 1;
+#endif
+}
+#endif
+
+/* DOCDOC */
+/* Requires lock */
+static int
+evbuffer_file_segment_materialize(struct evbuffer_file_segment *seg)
+{
+	const unsigned flags = seg->flags;
+	const int fd = seg->fd;
+	const ev_off_t length = seg->length;
+	const ev_off_t offset = seg->file_offset;
+
+	if (seg->contents)
+		return 0; /* already materialized */
+
+#if defined(EVENT__HAVE_MMAP)
+	if (!(flags & EVBUF_FS_DISABLE_MMAP)) {
+		off_t offset_rounded = 0, offset_leftover = 0;
+		void *mapped;
+		if (offset) {
+			/* mmap implementations don't generally like us
+			 * to have an offset that isn't a round  */
+			long page_size = get_page_size();
+			if (page_size == -1)
+				goto err;
+			offset_leftover = offset % page_size;
+			offset_rounded = offset - offset_leftover;
+		}
+		mapped = mmap(NULL, length + offset_leftover,
+		    PROT_READ,
+#ifdef MAP_NOCACHE
+		    MAP_NOCACHE | /* ??? */
+#endif
+#ifdef MAP_FILE
+		    MAP_FILE |
+#endif
+		    MAP_PRIVATE,
+		    fd, offset_rounded);
+		if (mapped == MAP_FAILED) {
+			event_warn("%s: mmap(%d, %d, %zu) failed",
+			    __func__, fd, 0, (size_t)(offset + length));
+		} else {
+			seg->mapping = mapped;
+			seg->contents = (char*)mapped+offset_leftover;
+			seg->mmap_offset = 0;
+			seg->is_mapping = 1;
+			goto done;
+		}
+	}
+#endif
+#ifdef _WIN32
+	if (!(flags & EVBUF_FS_DISABLE_MMAP)) {
+		intptr_t h = _get_osfhandle(fd);
+		HANDLE m;
+		ev_uint64_t total_size = length+offset;
+		if ((HANDLE)h == INVALID_HANDLE_VALUE)
+			goto err;
+		m = CreateFileMapping((HANDLE)h, NULL, PAGE_READONLY,
+		    (total_size >> 32), total_size & 0xfffffffful,
+		    NULL);
+		if (m != INVALID_HANDLE_VALUE) { /* Does h leak? */
+			seg->mapping_handle = m;
+			seg->mmap_offset = offset;
+			seg->is_mapping = 1;
+			goto done;
+		}
+	}
+#endif
+	{
+		ev_off_t start_pos = lseek(fd, 0, SEEK_CUR), pos;
+		ev_off_t read_so_far = 0;
+		char *mem;
+		int e;
+		ev_ssize_t n = 0;
+		if (!(mem = mm_malloc(length)))
+			goto err;
+		if (start_pos < 0) {
+			mm_free(mem);
+			goto err;
+		}
+		if (lseek(fd, offset, SEEK_SET) < 0) {
+			mm_free(mem);
+			goto err;
+		}
+		while (read_so_far < length) {
+			n = read(fd, mem+read_so_far, length-read_so_far);
+			if (n <= 0)
+				break;
+			read_so_far += n;
+		}
+
+		e = errno;
+		pos = lseek(fd, start_pos, SEEK_SET);
+		if (n < 0 || (n == 0 && length > read_so_far)) {
+			mm_free(mem);
+			errno = e;
+			goto err;
+		} else if (pos < 0) {
+			mm_free(mem);
+			goto err;
+		}
+
+		seg->contents = mem;
+	}
+
+done:
+	return 0;
+err:
+	return -1;
+}
+
+void evbuffer_file_segment_add_cleanup_cb(struct evbuffer_file_segment *seg,
+	evbuffer_file_segment_cleanup_cb cb, void* arg)
+{
+	EVUTIL_ASSERT(seg->refcnt > 0);
+	seg->cleanup_cb = cb;
+	seg->cleanup_cb_arg = arg;
+}
+
+void
+evbuffer_file_segment_free(struct evbuffer_file_segment *seg)
+{
+	int refcnt;
+	EVLOCK_LOCK(seg->lock, 0);
+	refcnt = --seg->refcnt;
+	EVLOCK_UNLOCK(seg->lock, 0);
+	if (refcnt > 0)
+		return;
+	EVUTIL_ASSERT(refcnt == 0);
+
+	if (seg->is_mapping) {
+#ifdef _WIN32
+		CloseHandle(seg->mapping_handle);
+#elif defined (EVENT__HAVE_MMAP)
+		off_t offset_leftover;
+		offset_leftover = seg->file_offset % get_page_size();
+		if (munmap(seg->mapping, seg->length + offset_leftover) == -1)
+			event_warn("%s: munmap failed", __func__);
+#endif
+	} else if (seg->contents) {
+		mm_free(seg->contents);
+	}
+
+	if ((seg->flags & EVBUF_FS_CLOSE_ON_FREE) && seg->fd >= 0) {
+		close(seg->fd);
+	}
+	
+	if (seg->cleanup_cb) {
+		(*seg->cleanup_cb)((struct evbuffer_file_segment const*)seg, 
+		    seg->flags, seg->cleanup_cb_arg);
+		seg->cleanup_cb = NULL;
+		seg->cleanup_cb_arg = NULL;
+	}
+
+	EVTHREAD_FREE_LOCK(seg->lock, 0);
+	mm_free(seg);
+}
+
+int
+evbuffer_add_file_segment(struct evbuffer *buf,
+    struct evbuffer_file_segment *seg, ev_off_t offset, ev_off_t length)
+{
+	struct evbuffer_chain *chain;
+	struct evbuffer_chain_file_segment *extra;
+	int can_use_sendfile = 0;
+
+	EVBUFFER_LOCK(buf);
+	EVLOCK_LOCK(seg->lock, 0);
+	if (buf->flags & EVBUFFER_FLAG_DRAINS_TO_FD) {
+		can_use_sendfile = 1;
+	} else {
+		if (!seg->contents) {
+			if (evbuffer_file_segment_materialize(seg)<0) {
+				EVLOCK_UNLOCK(seg->lock, 0);
+				EVBUFFER_UNLOCK(buf);
+				return -1;
+			}
+		}
+	}
+	EVLOCK_UNLOCK(seg->lock, 0);
+
+	if (buf->freeze_end)
+		goto err;
+
+	if (length < 0) {
+		if (offset > seg->length)
+			goto err;
+		length = seg->length - offset;
+	}
+
+	/* Can we actually add this? */
+	if (offset+length > seg->length)
+		goto err;
+
+	chain = evbuffer_chain_new(sizeof(struct evbuffer_chain_file_segment));
+	if (!chain)
+		goto err;
+	extra = EVBUFFER_CHAIN_EXTRA(struct evbuffer_chain_file_segment, chain);
+
+	chain->flags |= EVBUFFER_IMMUTABLE|EVBUFFER_FILESEGMENT;
+	if (can_use_sendfile && seg->can_sendfile) {
+		chain->flags |= EVBUFFER_SENDFILE;
+		chain->misalign = seg->file_offset + offset;
+		chain->off = length;
+		chain->buffer_len = chain->misalign + length;
+	} else if (seg->is_mapping) {
+#ifdef _WIN32
+		ev_uint64_t total_offset = seg->mmap_offset+offset;
+		ev_uint64_t offset_rounded=0, offset_remaining=0;
+		LPVOID data;
+		if (total_offset) {
+			SYSTEM_INFO si;
+			memset(&si, 0, sizeof(si)); /* cargo cult */
+			GetSystemInfo(&si);
+			offset_remaining = total_offset % si.dwAllocationGranularity;
+			offset_rounded = total_offset - offset_remaining;
+		}
+		data = MapViewOfFile(
+			seg->mapping_handle,
+			FILE_MAP_READ,
+			offset_rounded >> 32,
+			offset_rounded & 0xfffffffful,
+			length + offset_remaining);
+		if (data == NULL) {
+			mm_free(chain);
+			goto err;
+		}
+		chain->buffer = (unsigned char*) data;
+		chain->buffer_len = length+offset_remaining;
+		chain->misalign = offset_remaining;
+		chain->off = length;
+#else
+		chain->buffer = (unsigned char*)(seg->contents + offset);
+		chain->buffer_len = length;
+		chain->off = length;
+#endif
+	} else {
+		chain->buffer = (unsigned char*)(seg->contents + offset);
+		chain->buffer_len = length;
+		chain->off = length;
+	}
+
+	EVLOCK_LOCK(seg->lock, 0);
+	++seg->refcnt;
+	EVLOCK_UNLOCK(seg->lock, 0);
+	extra->segment = seg;
+	buf->n_add_for_cb += length;
+	evbuffer_chain_insert(buf, chain);
+
+	evbuffer_invoke_callbacks_(buf);
+
+	EVBUFFER_UNLOCK(buf);
+
+	return 0;
+err:
+	EVBUFFER_UNLOCK(buf);
+	evbuffer_file_segment_free(seg); /* Lowers the refcount */
+	return -1;
+}
+
+int
+evbuffer_add_file(struct evbuffer *buf, int fd, ev_off_t offset, ev_off_t length)
+{
+	struct evbuffer_file_segment *seg;
+	unsigned flags = EVBUF_FS_CLOSE_ON_FREE;
+	int r;
+
+	seg = evbuffer_file_segment_new(fd, offset, length, flags);
+	if (!seg)
+		return -1;
+	r = evbuffer_add_file_segment(buf, seg, 0, length);
+	if (r == 0)
+		evbuffer_file_segment_free(seg);
+	return r;
+}
+
+int
+evbuffer_setcb(struct evbuffer *buffer, evbuffer_cb cb, void *cbarg)
+{
+	EVBUFFER_LOCK(buffer);
+
+	if (!LIST_EMPTY(&buffer->callbacks))
+		evbuffer_remove_all_callbacks(buffer);
+
+	if (cb) {
+		struct evbuffer_cb_entry *ent =
+		    evbuffer_add_cb(buffer, NULL, cbarg);
+		if (!ent) {
+			EVBUFFER_UNLOCK(buffer);
+			return -1;
+		}
+		ent->cb.cb_obsolete = cb;
+		ent->flags |= EVBUFFER_CB_OBSOLETE;
+	}
+	EVBUFFER_UNLOCK(buffer);
+	return 0;
+}
+
+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;
+	LIST_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);
+	LIST_REMOVE(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);
+	LIST_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
+
+int
+evbuffer_get_callbacks_(struct evbuffer *buffer, struct event_callback **cbs,
+    int max_cbs)
+{
+	int r = 0;
+	EVBUFFER_LOCK(buffer);
+	if (buffer->deferred_cbs) {
+		if (max_cbs < 1) {
+			r = -1;
+			goto done;
+		}
+		cbs[0] = &buffer->deferred;
+		r = 1;
+	}
+done:
+	EVBUFFER_UNLOCK(buffer);
+	return r;
+}