Adding upstream version 1.0.18.upstream/1.0.18upstream

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

1 files changed, 1077 insertions, 0 deletions

diff --git a/libevent/include/event2/buffer.h b/libevent/include/event2/buffer.h
new file mode 100644
index 0000000..88af3ae
--- /dev/null
+++ b/libevent/include/event2/buffer.h
@@ -0,0 +1,1077 @@
+/*
+ * 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.
+ */
+#ifndef EVENT2_BUFFER_H_INCLUDED_
+#define EVENT2_BUFFER_H_INCLUDED_
+
+/** @file event2/buffer.h
+
+  Functions for buffering data for network sending or receiving.
+
+  An evbuffer can be used for preparing data before sending it to
+  the network or conversely for reading data from the network.
+  Evbuffers try to avoid memory copies as much as possible.  As a
+  result, evbuffers can be used to pass data around without actually
+  incurring the overhead of copying the data.
+
+  A new evbuffer can be allocated with evbuffer_new(), and can be
+  freed with evbuffer_free().  Most users will be using evbuffers via
+  the bufferevent interface.  To access a bufferevent's evbuffers, use
+  bufferevent_get_input() and bufferevent_get_output().
+
+  There are several guidelines for using evbuffers.
+
+  - if you already know how much data you are going to add as a result
+    of calling evbuffer_add() multiple times, it makes sense to use
+    evbuffer_expand() first to make sure that enough memory is allocated
+    before hand.
+
+  - evbuffer_add_buffer() adds the contents of one buffer to the other
+    without incurring any unnecessary memory copies.
+
+  - evbuffer_add() and evbuffer_add_buffer() do not mix very well:
+    if you use them, you will wind up with fragmented memory in your
+	buffer.
+
+  - For high-performance code, you may want to avoid copying data into and out
+    of buffers.  You can skip the copy step by using
+    evbuffer_reserve_space()/evbuffer_commit_space() when writing into a
+    buffer, and evbuffer_peek() when reading.
+
+  In Libevent 2.0 and later, evbuffers are represented using a linked
+  list of memory chunks, with pointers to the first and last chunk in
+  the chain.
+
+  As the contents of an evbuffer can be stored in multiple different
+  memory blocks, it cannot be accessed directly.  Instead, evbuffer_pullup()
+  can be used to force a specified number of bytes to be contiguous. This
+  will cause memory reallocation and memory copies if the data is split
+  across multiple blocks.  It is more efficient, however, to use
+  evbuffer_peek() if you don't require that the memory to be contiguous.
+ */
+
+#include <event2/visibility.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <event2/event-config.h>
+#include <stdarg.h>
+#ifdef EVENT__HAVE_SYS_TYPES_H
+#include <sys/types.h>
+#endif
+#ifdef EVENT__HAVE_SYS_UIO_H
+#include <sys/uio.h>
+#endif
+#include <event2/util.h>
+
+/**
+   An evbuffer is an opaque data type for efficiently buffering data to be
+   sent or received on the network.
+
+   @see event2/event.h for more information
+*/
+struct evbuffer
+#ifdef EVENT_IN_DOXYGEN_
+{}
+#endif
+;
+
+/**
+    Pointer to a position within an evbuffer.
+
+    Used when repeatedly searching through a buffer.  Calling any function
+    that modifies or re-packs the buffer contents may invalidate all
+    evbuffer_ptrs for that buffer.  Do not modify or contruct these values
+    except with evbuffer_ptr_set.
+
+    An evbuffer_ptr can represent any position from the start of a buffer up
+    to a position immediately after the end of a buffer.
+
+    @see evbuffer_ptr_set()
+ */
+struct evbuffer_ptr {
+	ev_ssize_t pos;
+
+	/* Do not alter or rely on the values of fields: they are for internal
+	 * use */
+	struct {
+		void *chain;
+		size_t pos_in_chain;
+	} internal_;
+};
+
+/** Describes a single extent of memory inside an evbuffer.  Used for
+    direct-access functions.
+
+    @see evbuffer_reserve_space, evbuffer_commit_space, evbuffer_peek
+ */
+#ifdef EVENT__HAVE_SYS_UIO_H
+#define evbuffer_iovec iovec
+/* Internal use -- defined only if we are using the native struct iovec */
+#define EVBUFFER_IOVEC_IS_NATIVE_
+#else
+struct evbuffer_iovec {
+	/** The start of the extent of memory. */
+	void *iov_base;
+	/** The length of the extent of memory. */
+	size_t iov_len;
+};
+#endif
+
+/**
+  Allocate storage for a new evbuffer.
+
+  @return a pointer to a newly allocated evbuffer struct, or NULL if an error
+	occurred
+ */
+EVENT2_EXPORT_SYMBOL
+struct evbuffer *evbuffer_new(void);
+/**
+  Deallocate storage for an evbuffer.
+
+  @param buf pointer to the evbuffer to be freed
+ */
+EVENT2_EXPORT_SYMBOL
+void evbuffer_free(struct evbuffer *buf);
+
+/**
+   Enable locking on an evbuffer so that it can safely be used by multiple
+   threads at the same time.
+
+   NOTE: when locking is enabled, the lock will be held when callbacks are
+   invoked.  This could result in deadlock if you aren't careful.  Plan
+   accordingly!
+
+   @param buf An evbuffer to make lockable.
+   @param lock A lock object, or NULL if we should allocate our own.
+   @return 0 on success, -1 on failure.
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_enable_locking(struct evbuffer *buf, void *lock);
+
+/**
+   Acquire the lock on an evbuffer.  Has no effect if locking was not enabled
+   with evbuffer_enable_locking.
+*/
+EVENT2_EXPORT_SYMBOL
+void evbuffer_lock(struct evbuffer *buf);
+
+/**
+   Release the lock on an evbuffer.  Has no effect if locking was not enabled
+   with evbuffer_enable_locking.
+*/
+EVENT2_EXPORT_SYMBOL
+void evbuffer_unlock(struct evbuffer *buf);
+
+
+/** If this flag is set, then we will not use evbuffer_peek(),
+ * evbuffer_remove(), evbuffer_remove_buffer(), and so on to read bytes
+ * from this buffer: we'll only take bytes out of this buffer by
+ * writing them to the network (as with evbuffer_write_atmost), by
+ * removing them without observing them (as with evbuffer_drain),
+ * or by copying them all out at once (as with evbuffer_add_buffer).
+ *
+ * Using this option allows the implementation to use sendfile-based
+ * operations for evbuffer_add_file(); see that function for more
+ * information.
+ *
+ * This flag is on by default for bufferevents that can take advantage
+ * of it; you should never actually need to set it on a bufferevent's
+ * output buffer.
+ */
+#define EVBUFFER_FLAG_DRAINS_TO_FD 1
+
+/** Change the flags that are set for an evbuffer by adding more.
+ *
+ * @param buffer the evbuffer that the callback is watching.
+ * @param cb the callback whose status we want to change.
+ * @param flags One or more EVBUFFER_FLAG_* options
+ * @return 0 on success, -1 on failure.
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_set_flags(struct evbuffer *buf, ev_uint64_t flags);
+/** Change the flags that are set for an evbuffer by removing some.
+ *
+ * @param buffer the evbuffer that the callback is watching.
+ * @param cb the callback whose status we want to change.
+ * @param flags One or more EVBUFFER_FLAG_* options
+ * @return 0 on success, -1 on failure.
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_clear_flags(struct evbuffer *buf, ev_uint64_t flags);
+
+/**
+  Returns the total number of bytes stored in the evbuffer
+
+  @param buf pointer to the evbuffer
+  @return the number of bytes stored in the evbuffer
+*/
+EVENT2_EXPORT_SYMBOL
+size_t evbuffer_get_length(const struct evbuffer *buf);
+
+/**
+   Returns the number of contiguous available bytes in the first buffer chain.
+
+   This is useful when processing data that might be split into multiple
+   chains, or that might all be in the first chain.  Calls to
+   evbuffer_pullup() that cause reallocation and copying of data can thus be
+   avoided.
+
+   @param buf pointer to the evbuffer
+   @return 0 if no data is available, otherwise the number of available bytes
+     in the first buffer chain.
+*/
+EVENT2_EXPORT_SYMBOL
+size_t evbuffer_get_contiguous_space(const struct evbuffer *buf);
+
+/**
+  Expands the available space in an evbuffer.
+
+  Expands the available space in the evbuffer to at least datlen, so that
+  appending datlen additional bytes will not require any new allocations.
+
+  @param buf the evbuffer to be expanded
+  @param datlen the new minimum length requirement
+  @return 0 if successful, or -1 if an error occurred
+*/
+EVENT2_EXPORT_SYMBOL
+int evbuffer_expand(struct evbuffer *buf, size_t datlen);
+
+/**
+   Reserves space in the last chain or chains of an evbuffer.
+
+   Makes space available in the last chain or chains of an evbuffer that can
+   be arbitrarily written to by a user.  The space does not become
+   available for reading until it has been committed with
+   evbuffer_commit_space().
+
+   The space is made available as one or more extents, represented by
+   an initial pointer and a length.  You can force the memory to be
+   available as only one extent.  Allowing more extents, however, makes the
+   function more efficient.
+
+   Multiple subsequent calls to this function will make the same space
+   available until evbuffer_commit_space() has been called.
+
+   It is an error to do anything that moves around the buffer's internal
+   memory structures before committing the space.
+
+   NOTE: The code currently does not ever use more than two extents.
+   This may change in future versions.
+
+   @param buf the evbuffer in which to reserve space.
+   @param size how much space to make available, at minimum.  The
+      total length of the extents may be greater than the requested
+      length.
+   @param vec an array of one or more evbuffer_iovec structures to
+      hold pointers to the reserved extents of memory.
+   @param n_vec The length of the vec array.  Must be at least 1;
+       2 is more efficient.
+   @return the number of provided extents, or -1 on error.
+   @see evbuffer_commit_space()
+*/
+EVENT2_EXPORT_SYMBOL
+int
+evbuffer_reserve_space(struct evbuffer *buf, ev_ssize_t size,
+    struct evbuffer_iovec *vec, int n_vec);
+
+/**
+   Commits previously reserved space.
+
+   Commits some of the space previously reserved with
+   evbuffer_reserve_space().  It then becomes available for reading.
+
+   This function may return an error if the pointer in the extents do
+   not match those returned from evbuffer_reserve_space, or if data
+   has been added to the buffer since the space was reserved.
+
+   If you want to commit less data than you got reserved space for,
+   modify the iov_len pointer of the appropriate extent to a smaller
+   value.  Note that you may have received more space than you
+   requested if it was available!
+
+   @param buf the evbuffer in which to reserve space.
+   @param vec one or two extents returned by evbuffer_reserve_space.
+   @param n_vecs the number of extents.
+   @return 0 on success, -1 on error
+   @see evbuffer_reserve_space()
+*/
+EVENT2_EXPORT_SYMBOL
+int evbuffer_commit_space(struct evbuffer *buf,
+    struct evbuffer_iovec *vec, int n_vecs);
+
+/**
+  Append data to the end of an evbuffer.
+
+  @param buf the evbuffer to be appended to
+  @param data pointer to the beginning of the data buffer
+  @param datlen the number of bytes to be copied from the data buffer
+  @return 0 on success, -1 on failure.
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_add(struct evbuffer *buf, const void *data, size_t datlen);
+
+
+/**
+  Read data from an evbuffer and drain the bytes read.
+
+  If more bytes are requested than are available in the evbuffer, we
+  only extract as many bytes as were available.
+
+  @param buf the evbuffer to be read from
+  @param data the destination buffer to store the result
+  @param datlen the maximum size of the destination buffer
+  @return the number of bytes read, or -1 if we can't drain the buffer.
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_remove(struct evbuffer *buf, void *data, size_t datlen);
+
+/**
+  Read data from an evbuffer, and leave the buffer unchanged.
+
+  If more bytes are requested than are available in the evbuffer, we
+  only extract as many bytes as were available.
+
+  @param buf the evbuffer to be read from
+  @param data_out the destination buffer to store the result
+  @param datlen the maximum size of the destination buffer
+  @return the number of bytes read, or -1 if we can't drain the buffer.
+ */
+EVENT2_EXPORT_SYMBOL
+ev_ssize_t evbuffer_copyout(struct evbuffer *buf, void *data_out, size_t datlen);
+
+/**
+  Read data from the middle of an evbuffer, and leave the buffer unchanged.
+
+  If more bytes are requested than are available in the evbuffer, we
+  only extract as many bytes as were available.
+
+  @param buf the evbuffer to be read from
+  @param pos the position to start reading from
+  @param data_out the destination buffer to store the result
+  @param datlen the maximum size of the destination buffer
+  @return the number of bytes read, or -1 if we can't drain the buffer.
+ */
+EVENT2_EXPORT_SYMBOL
+ev_ssize_t evbuffer_copyout_from(struct evbuffer *buf, const struct evbuffer_ptr *pos, void *data_out, size_t datlen);
+
+/**
+  Read data from an evbuffer into another evbuffer, draining
+  the bytes from the source buffer.  This function avoids copy
+  operations to the extent possible.
+
+  If more bytes are requested than are available in src, the src
+  buffer is drained completely.
+
+  @param src the evbuffer to be read from
+  @param dst the destination evbuffer to store the result into
+  @param datlen the maximum numbers of bytes to transfer
+  @return the number of bytes read
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_remove_buffer(struct evbuffer *src, struct evbuffer *dst,
+    size_t datlen);
+
+/** Used to tell evbuffer_readln what kind of line-ending to look for.
+ */
+enum evbuffer_eol_style {
+	/** Any sequence of CR and LF characters is acceptable as an
+	 * EOL.
+	 *
+	 * Note that this style can produce ambiguous results: the
+	 * sequence "CRLF" will be treated as a single EOL if it is
+	 * all in the buffer at once, but if you first read a CR from
+	 * the network and later read an LF from the network, it will
+	 * be treated as two EOLs.
+	 */
+	EVBUFFER_EOL_ANY,
+	/** An EOL is an LF, optionally preceded by a CR.  This style is
+	 * most useful for implementing text-based internet protocols. */
+	EVBUFFER_EOL_CRLF,
+	/** An EOL is a CR followed by an LF. */
+	EVBUFFER_EOL_CRLF_STRICT,
+	/** An EOL is a LF. */
+	EVBUFFER_EOL_LF,
+	/** An EOL is a NUL character (that is, a single byte with value 0) */
+	EVBUFFER_EOL_NUL
+};
+
+/**
+ * Read a single line from an evbuffer.
+ *
+ * Reads a line terminated by an EOL as determined by the evbuffer_eol_style
+ * argument.  Returns a newly allocated nul-terminated string; the caller must
+ * free the returned value.  The EOL is not included in the returned string.
+ *
+ * @param buffer the evbuffer to read from
+ * @param n_read_out if non-NULL, points to a size_t that is set to the
+ *       number of characters in the returned string.  This is useful for
+ *       strings that can contain NUL characters.
+ * @param eol_style the style of line-ending to use.
+ * @return pointer to a single line, or NULL if an error occurred
+ */
+EVENT2_EXPORT_SYMBOL
+char *evbuffer_readln(struct evbuffer *buffer, size_t *n_read_out,
+    enum evbuffer_eol_style eol_style);
+
+/**
+  Move all data from one evbuffer into another evbuffer.
+
+  This is a destructive add.  The data from one buffer moves into
+  the other buffer.  However, no unnecessary memory copies occur.
+
+  @param outbuf the output buffer
+  @param inbuf the input buffer
+  @return 0 if successful, or -1 if an error occurred
+
+  @see evbuffer_remove_buffer()
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_add_buffer(struct evbuffer *outbuf, struct evbuffer *inbuf);
+
+/**
+  Copy data from one evbuffer into another evbuffer.
+
+  This is a non-destructive add.  The data from one buffer is copied
+  into the other buffer.  However, no unnecessary memory copies occur.
+
+  Note that buffers already containing buffer references can't be added
+  to other buffers.
+
+  @param outbuf the output buffer
+  @param inbuf the input buffer
+  @return 0 if successful, or -1 if an error occurred
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_add_buffer_reference(struct evbuffer *outbuf,
+    struct evbuffer *inbuf);
+
+/**
+   A cleanup function for a piece of memory added to an evbuffer by
+   reference.
+
+   @see evbuffer_add_reference()
+ */
+typedef void (*evbuffer_ref_cleanup_cb)(const void *data,
+    size_t datalen, void *extra);
+
+/**
+  Reference memory into an evbuffer without copying.
+
+  The memory needs to remain valid until all the added data has been
+  read.  This function keeps just a reference to the memory without
+  actually incurring the overhead of a copy.
+
+  @param outbuf the output buffer
+  @param data the memory to reference
+  @param datlen how memory to reference
+  @param cleanupfn callback to be invoked when the memory is no longer
+	referenced by this evbuffer.
+  @param cleanupfn_arg optional argument to the cleanup callback
+  @return 0 if successful, or -1 if an error occurred
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_add_reference(struct evbuffer *outbuf,
+    const void *data, size_t datlen,
+    evbuffer_ref_cleanup_cb cleanupfn, void *cleanupfn_arg);
+
+/**
+  Copy data from a file into the evbuffer for writing to a socket.
+
+  This function avoids unnecessary data copies between userland and
+  kernel.  If sendfile is available and the EVBUFFER_FLAG_DRAINS_TO_FD
+  flag is set, it uses those functions.  Otherwise, it tries to use
+  mmap (or CreateFileMapping on Windows).
+
+  The function owns the resulting file descriptor and will close it
+  when finished transferring data.
+
+  The results of using evbuffer_remove() or evbuffer_pullup() on
+  evbuffers whose data was added using this function are undefined.
+
+  For more fine-grained control, use evbuffer_add_file_segment.
+
+  @param outbuf the output buffer
+  @param fd the file descriptor
+  @param offset the offset from which to read data
+  @param length how much data to read, or -1 to read as much as possible.
+    (-1 requires that 'fd' support fstat.)
+  @return 0 if successful, or -1 if an error occurred
+*/
+
+EVENT2_EXPORT_SYMBOL
+int evbuffer_add_file(struct evbuffer *outbuf, int fd, ev_off_t offset,
+    ev_off_t length);
+
+/**
+  An evbuffer_file_segment holds a reference to a range of a file --
+  possibly the whole file! -- for use in writing from an evbuffer to a
+  socket.  It could be implemented with mmap, sendfile, splice, or (if all
+  else fails) by just pulling all the data into RAM.  A single
+  evbuffer_file_segment can be added more than once, and to more than one
+  evbuffer.
+ */
+struct evbuffer_file_segment;
+
+/**
+    Flag for creating evbuffer_file_segment: If this flag is set, then when
+    the evbuffer_file_segment is freed and no longer in use by any
+    evbuffer, the underlying fd is closed.
+ */
+#define EVBUF_FS_CLOSE_ON_FREE    0x01
+/**
+   Flag for creating evbuffer_file_segment: Disable memory-map based
+   implementations.
+ */
+#define EVBUF_FS_DISABLE_MMAP     0x02
+/**
+   Flag for creating evbuffer_file_segment: Disable direct fd-to-fd
+   implementations (including sendfile and splice).
+
+   You might want to use this option if data needs to be taken from the
+   evbuffer by any means other than writing it to the network: the sendfile
+   backend is fast, but it only works for sending files directly to the
+   network.
+ */
+#define EVBUF_FS_DISABLE_SENDFILE 0x04
+/**
+   Flag for creating evbuffer_file_segment: Do not allocate a lock for this
+   segment.  If this option is set, then neither the segment nor any
+   evbuffer it is added to may ever be accessed from more than one thread
+   at a time.
+ */
+#define EVBUF_FS_DISABLE_LOCKING  0x08
+
+/**
+   A cleanup function for a evbuffer_file_segment added to an evbuffer
+   for reference.
+ */
+typedef void (*evbuffer_file_segment_cleanup_cb)(
+    struct evbuffer_file_segment const* seg, int flags, void* arg);
+
+/**
+   Create and return a new evbuffer_file_segment for reading data from a
+   file and sending it out via an evbuffer.
+
+   This function avoids unnecessary data copies between userland and
+   kernel.  Where available, it uses sendfile or splice.
+
+   The file descriptor must not be closed so long as any evbuffer is using
+   this segment.
+
+   The results of using evbuffer_remove() or evbuffer_pullup() or any other
+   function that reads bytes from an evbuffer on any evbuffer containing
+   the newly returned segment are undefined, unless you pass the
+   EVBUF_FS_DISABLE_SENDFILE flag to this function.
+
+   @param fd an open file to read from.
+   @param offset an index within the file at which to start reading
+   @param length how much data to read, or -1 to read as much as possible.
+      (-1 requires that 'fd' support fstat.)
+   @param flags any number of the EVBUF_FS_* flags
+   @return a new evbuffer_file_segment, or NULL on failure.
+ **/
+EVENT2_EXPORT_SYMBOL
+struct evbuffer_file_segment *evbuffer_file_segment_new(
+	int fd, ev_off_t offset, ev_off_t length, unsigned flags);
+
+/**
+   Free an evbuffer_file_segment
+
+   It is safe to call this function even if the segment has been added to
+   one or more evbuffers.  The evbuffer_file_segment will not be freed
+   until no more references to it exist.
+ */
+EVENT2_EXPORT_SYMBOL
+void evbuffer_file_segment_free(struct evbuffer_file_segment *seg);
+
+/**
+   Add cleanup callback and argument for the callback to an
+   evbuffer_file_segment.
+
+   The cleanup callback will be invoked when no more references to the
+   evbuffer_file_segment exist.
+ **/
+EVENT2_EXPORT_SYMBOL
+void evbuffer_file_segment_add_cleanup_cb(struct evbuffer_file_segment *seg,
+	evbuffer_file_segment_cleanup_cb cb, void* arg);
+
+/**
+   Insert some or all of an evbuffer_file_segment at the end of an evbuffer
+
+   Note that the offset and length parameters of this function have a
+   different meaning from those provided to evbuffer_file_segment_new: When
+   you create the segment, the offset is the offset _within the file_, and
+   the length is the length _of the segment_, whereas when you add a
+   segment to an evbuffer, the offset is _within the segment_ and the
+   length is the length of the _part of the segment you want to use.
+
+   In other words, if you have a 10 KiB file, and you create an
+   evbuffer_file_segment for it with offset 20 and length 1000, it will
+   refer to bytes 20..1019 inclusive.  If you then pass this segment to
+   evbuffer_add_file_segment and specify an offset of 20 and a length of
+   50, you will be adding bytes 40..99 inclusive.
+
+   @param buf the evbuffer to append to
+   @param seg the segment to add
+   @param offset the offset within the segment to start from
+   @param length the amount of data to add, or -1 to add it all.
+   @return 0 on success, -1 on failure.
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_add_file_segment(struct evbuffer *buf,
+    struct evbuffer_file_segment *seg, ev_off_t offset, ev_off_t length);
+
+/**
+  Append a formatted string to the end of an evbuffer.
+
+  The string is formated as printf.
+
+  @param buf the evbuffer that will be appended to
+  @param fmt a format string
+  @param ... arguments that will be passed to printf(3)
+  @return The number of bytes added if successful, or -1 if an error occurred.
+
+  @see evutil_printf(), evbuffer_add_vprintf()
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_add_printf(struct evbuffer *buf, const char *fmt, ...)
+#ifdef __GNUC__
+  __attribute__((format(printf, 2, 3)))
+#endif
+;
+
+/**
+  Append a va_list formatted string to the end of an evbuffer.
+
+  @param buf the evbuffer that will be appended to
+  @param fmt a format string
+  @param ap a varargs va_list argument array that will be passed to vprintf(3)
+  @return The number of bytes added if successful, or -1 if an error occurred.
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_add_vprintf(struct evbuffer *buf, const char *fmt, va_list ap)
+#ifdef __GNUC__
+	__attribute__((format(printf, 2, 0)))
+#endif
+;
+
+
+/**
+  Remove a specified number of bytes data from the beginning of an evbuffer.
+
+  @param buf the evbuffer to be drained
+  @param len the number of bytes to drain from the beginning of the buffer
+  @return 0 on success, -1 on failure.
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_drain(struct evbuffer *buf, size_t len);
+
+
+/**
+  Write the contents of an evbuffer to a file descriptor.
+
+  The evbuffer will be drained after the bytes have been successfully written.
+
+  @param buffer the evbuffer to be written and drained
+  @param fd the file descriptor to be written to
+  @return the number of bytes written, or -1 if an error occurred
+  @see evbuffer_read()
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_write(struct evbuffer *buffer, evutil_socket_t fd);
+
+/**
+  Write some of the contents of an evbuffer to a file descriptor.
+
+  The evbuffer will be drained after the bytes have been successfully written.
+
+  @param buffer the evbuffer to be written and drained
+  @param fd the file descriptor to be written to
+  @param howmuch the largest allowable number of bytes to write, or -1
+	to write as many bytes as we can.
+  @return the number of bytes written, or -1 if an error occurred
+  @see evbuffer_read()
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_write_atmost(struct evbuffer *buffer, evutil_socket_t fd,
+						  ev_ssize_t howmuch);
+
+/**
+  Read from a file descriptor and store the result in an evbuffer.
+
+  @param buffer the evbuffer to store the result
+  @param fd the file descriptor to read from
+  @param howmuch the number of bytes to be read. If the given number is negative
+  or out of maximum bytes per one read, as many bytes as we can will be read.
+  @return the number of bytes read, or -1 if an error occurred
+  @see evbuffer_write()
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_read(struct evbuffer *buffer, evutil_socket_t fd, int howmuch);
+
+/**
+   Search for a string within an evbuffer.
+
+   @param buffer the evbuffer to be searched
+   @param what the string to be searched for
+   @param len the length of the search string
+   @param start NULL or a pointer to a valid struct evbuffer_ptr.
+   @return a struct evbuffer_ptr whose 'pos' field has the offset of the
+     first occurrence of the string in the buffer after 'start'.  The 'pos'
+     field of the result is -1 if the string was not found.
+ */
+EVENT2_EXPORT_SYMBOL
+struct evbuffer_ptr evbuffer_search(struct evbuffer *buffer, const char *what, size_t len, const struct evbuffer_ptr *start);
+
+/**
+   Search for a string within part of an evbuffer.
+
+   @param buffer the evbuffer to be searched
+   @param what the string to be searched for
+   @param len the length of the search string
+   @param start NULL or a pointer to a valid struct evbuffer_ptr that
+     indicates where we should start searching.
+   @param end NULL or a pointer to a valid struct evbuffer_ptr that
+     indicates where we should stop searching.
+   @return a struct evbuffer_ptr whose 'pos' field has the offset of the
+     first occurrence of the string in the buffer after 'start'.  The 'pos'
+     field of the result is -1 if the string was not found.
+ */
+EVENT2_EXPORT_SYMBOL
+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);
+
+/**
+   Defines how to adjust an evbuffer_ptr by evbuffer_ptr_set()
+
+   @see evbuffer_ptr_set() */
+enum evbuffer_ptr_how {
+	/** Sets the pointer to the position; can be called on with an
+	    uninitialized evbuffer_ptr. */
+	EVBUFFER_PTR_SET,
+	/** Advances the pointer by adding to the current position. */
+	EVBUFFER_PTR_ADD
+};
+
+/**
+   Sets the search pointer in the buffer to position.
+
+   There are two ways to use this function: you can call
+      evbuffer_ptr_set(buf, &pos, N, EVBUFFER_PTR_SET)
+   to move 'pos' to a position 'N' bytes after the start of the buffer, or
+      evbuffer_ptr_set(buf, &pos, N, EVBUFFER_PTR_ADD)
+   to move 'pos' forward by 'N' bytes.
+
+   If evbuffer_ptr is not initialized, this function can only be called
+   with EVBUFFER_PTR_SET.
+
+   An evbuffer_ptr can represent any position from the start of the buffer to
+   a position immediately after the end of the buffer.
+
+   @param buffer the evbuffer to be search
+   @param ptr a pointer to a struct evbuffer_ptr
+   @param position the position at which to start the next search
+   @param how determines how the pointer should be manipulated.
+   @returns 0 on success or -1 otherwise
+*/
+EVENT2_EXPORT_SYMBOL
+int
+evbuffer_ptr_set(struct evbuffer *buffer, struct evbuffer_ptr *ptr,
+    size_t position, enum evbuffer_ptr_how how);
+
+/**
+   Search for an end-of-line string within an evbuffer.
+
+   @param buffer the evbuffer to be searched
+   @param start NULL or a pointer to a valid struct evbuffer_ptr to start
+      searching at.
+   @param eol_len_out If non-NULL, the pointed-to value will be set to
+      the length of the end-of-line string.
+   @param eol_style The kind of EOL to look for; see evbuffer_readln() for
+      more information
+   @return a struct evbuffer_ptr whose 'pos' field has the offset of the
+     first occurrence EOL in the buffer after 'start'.  The 'pos'
+     field of the result is -1 if the string was not found.
+ */
+EVENT2_EXPORT_SYMBOL
+struct evbuffer_ptr evbuffer_search_eol(struct evbuffer *buffer,
+    struct evbuffer_ptr *start, size_t *eol_len_out,
+    enum evbuffer_eol_style eol_style);
+
+/** Function to peek at data inside an evbuffer without removing it or
+    copying it out.
+
+    Pointers to the data are returned by filling the 'vec_out' array
+    with pointers to one or more extents of data inside the buffer.
+
+    The total data in the extents that you get back may be more than
+    you requested (if there is more data last extent than you asked
+    for), or less (if you do not provide enough evbuffer_iovecs, or if
+    the buffer does not have as much data as you asked to see).
+
+    @param buffer the evbuffer to peek into,
+    @param len the number of bytes to try to peek.  If len is negative, we
+       will try to fill as much of vec_out as we can.  If len is negative
+       and vec_out is not provided, we return the number of evbuffer_iovecs
+       that would be needed to get all the data in the buffer.
+    @param start_at an evbuffer_ptr indicating the point at which we
+       should start looking for data.  NULL means, "At the start of the
+       buffer."
+    @param vec_out an array of evbuffer_iovec
+    @param n_vec the length of vec_out.  If 0, we only count how many
+       extents would be necessary to point to the requested amount of
+       data.
+    @return The number of extents needed.  This may be less than n_vec
+       if we didn't need all the evbuffer_iovecs we were given, or more
+       than n_vec if we would need more to return all the data that was
+       requested.
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_peek(struct evbuffer *buffer, ev_ssize_t len,
+    struct evbuffer_ptr *start_at,
+    struct evbuffer_iovec *vec_out, int n_vec);
+
+
+/** Structure passed to an evbuffer_cb_func evbuffer callback
+
+    @see evbuffer_cb_func, evbuffer_add_cb()
+ */
+struct evbuffer_cb_info {
+	/** The number of bytes in this evbuffer when callbacks were last
+	 * invoked. */
+	size_t orig_size;
+	/** The number of bytes added since callbacks were last invoked. */
+	size_t n_added;
+	/** The number of bytes removed since callbacks were last invoked. */
+	size_t n_deleted;
+};
+
+/** Type definition for a callback that is invoked whenever data is added or
+    removed from an evbuffer.
+
+    An evbuffer may have one or more callbacks set at a time.  The order
+    in which they are executed is undefined.
+
+    A callback function may add more callbacks, or remove itself from the
+    list of callbacks, or add or remove data from the buffer.  It may not
+    remove another callback from the list.
+
+    If a callback adds or removes data from the buffer or from another
+    buffer, this can cause a recursive invocation of your callback or
+    other callbacks.  If you ask for an infinite loop, you might just get
+    one: watch out!
+
+    @param buffer the buffer whose size has changed
+    @param info a structure describing how the buffer changed.
+    @param arg a pointer to user data
+*/
+typedef void (*evbuffer_cb_func)(struct evbuffer *buffer, const struct evbuffer_cb_info *info, void *arg);
+
+struct evbuffer_cb_entry;
+/** Add a new callback to an evbuffer.
+
+  Subsequent calls to evbuffer_add_cb() add new callbacks.  To remove this
+  callback, call evbuffer_remove_cb or evbuffer_remove_cb_entry.
+
+  @param buffer the evbuffer to be monitored
+  @param cb the callback function to invoke when the evbuffer is modified,
+	or NULL to remove all callbacks.
+  @param cbarg an argument to be provided to the callback function
+  @return a handle to the callback on success, or NULL on failure.
+ */
+EVENT2_EXPORT_SYMBOL
+struct evbuffer_cb_entry *evbuffer_add_cb(struct evbuffer *buffer, evbuffer_cb_func cb, void *cbarg);
+
+/** Remove a callback from an evbuffer, given a handle returned from
+    evbuffer_add_cb.
+
+    Calling this function invalidates the handle.
+
+    @return 0 if a callback was removed, or -1 if no matching callback was
+    found.
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_remove_cb_entry(struct evbuffer *buffer,
+			     struct evbuffer_cb_entry *ent);
+
+/** Remove a callback from an evbuffer, given the function and argument
+    used to add it.
+
+    @return 0 if a callback was removed, or -1 if no matching callback was
+    found.
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_remove_cb(struct evbuffer *buffer, evbuffer_cb_func cb, void *cbarg);
+
+/** If this flag is not set, then a callback is temporarily disabled, and
+ * should not be invoked.
+ *
+ * @see evbuffer_cb_set_flags(), evbuffer_cb_clear_flags()
+ */
+#define EVBUFFER_CB_ENABLED 1
+
+/** Change the flags that are set for a callback on a buffer by adding more.
+
+    @param buffer the evbuffer that the callback is watching.
+    @param cb the callback whose status we want to change.
+    @param flags EVBUFFER_CB_ENABLED to re-enable the callback.
+    @return 0 on success, -1 on failure.
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_cb_set_flags(struct evbuffer *buffer,
+			  struct evbuffer_cb_entry *cb, ev_uint32_t flags);
+
+/** Change the flags that are set for a callback on a buffer by removing some
+
+    @param buffer the evbuffer that the callback is watching.
+    @param cb the callback whose status we want to change.
+    @param flags EVBUFFER_CB_ENABLED to disable the callback.
+    @return 0 on success, -1 on failure.
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_cb_clear_flags(struct evbuffer *buffer,
+			  struct evbuffer_cb_entry *cb, ev_uint32_t flags);
+
+#if 0
+/** Postpone calling a given callback until unsuspend is called later.
+
+    This is different from disabling the callback, since the callback will get
+	invoked later if the buffer size changes between now and when we unsuspend
+	it.
+
+	@param the buffer that the callback is watching.
+	@param cb the callback we want to suspend.
+ */
+EVENT2_EXPORT_SYMBOL
+void evbuffer_cb_suspend(struct evbuffer *buffer, struct evbuffer_cb_entry *cb);
+/** Stop postponing a callback that we postponed with evbuffer_cb_suspend.
+
+	If data was added to or removed from the buffer while the callback was
+	suspended, the callback will get called once now.
+
+	@param the buffer that the callback is watching.
+	@param cb the callback we want to stop suspending.
+ */
+EVENT2_EXPORT_SYMBOL
+void evbuffer_cb_unsuspend(struct evbuffer *buffer, struct evbuffer_cb_entry *cb);
+#endif
+
+/**
+  Makes the data at the beginning of an evbuffer contiguous.
+
+  @param buf the evbuffer to make contiguous
+  @param size the number of bytes to make contiguous, or -1 to make the
+	entire buffer contiguous.
+  @return a pointer to the contiguous memory array, or NULL if param size
+	requested more data than is present in the buffer.
+*/
+
+EVENT2_EXPORT_SYMBOL
+unsigned char *evbuffer_pullup(struct evbuffer *buf, ev_ssize_t size);
+
+/**
+  Prepends data to the beginning of the evbuffer
+
+  @param buf the evbuffer to which to prepend data
+  @param data a pointer to the memory to prepend
+  @param size the number of bytes to prepend
+  @return 0 if successful, or -1 otherwise
+*/
+
+EVENT2_EXPORT_SYMBOL
+int evbuffer_prepend(struct evbuffer *buf, const void *data, size_t size);
+
+/**
+  Prepends all data from the src evbuffer to the beginning of the dst
+  evbuffer.
+
+  @param dst the evbuffer to which to prepend data
+  @param src the evbuffer to prepend; it will be emptied as a result
+  @return 0 if successful, or -1 otherwise
+*/
+EVENT2_EXPORT_SYMBOL
+int evbuffer_prepend_buffer(struct evbuffer *dst, struct evbuffer* src);
+
+/**
+   Prevent calls that modify an evbuffer from succeeding. A buffer may
+   frozen at the front, at the back, or at both the front and the back.
+
+   If the front of a buffer is frozen, operations that drain data from
+   the front of the buffer, or that prepend data to the buffer, will
+   fail until it is unfrozen.   If the back a buffer is frozen, operations
+   that append data from the buffer will fail until it is unfrozen.
+
+   @param buf The buffer to freeze
+   @param at_front If true, we freeze the front of the buffer.  If false,
+      we freeze the back.
+   @return 0 on success, -1 on failure.
+*/
+EVENT2_EXPORT_SYMBOL
+int evbuffer_freeze(struct evbuffer *buf, int at_front);
+/**
+   Re-enable calls that modify an evbuffer.
+
+   @param buf The buffer to un-freeze
+   @param at_front If true, we unfreeze the front of the buffer.  If false,
+      we unfreeze the back.
+   @return 0 on success, -1 on failure.
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_unfreeze(struct evbuffer *buf, int at_front);
+
+struct event_base;
+/**
+   Force all the callbacks on an evbuffer to be run, not immediately after
+   the evbuffer is altered, but instead from inside the event loop.
+
+   This can be used to serialize all the callbacks to a single thread
+   of execution.
+ */
+EVENT2_EXPORT_SYMBOL
+int evbuffer_defer_callbacks(struct evbuffer *buffer, struct event_base *base);
+
+/**
+  Append data from 1 or more iovec's to an evbuffer
+
+  Calculates the number of bytes needed for an iovec structure and guarantees
+  all data will fit into a single chain. Can be used in lieu of functionality
+  which calls evbuffer_add() constantly before being used to increase
+  performance.
+
+  @param buffer the destination buffer
+  @param vec the source iovec
+  @param n_vec the number of iovec structures.
+  @return the number of bytes successfully written to the output buffer.
+*/
+EVENT2_EXPORT_SYMBOL
+size_t evbuffer_add_iovec(struct evbuffer * buffer, struct evbuffer_iovec * vec, int n_vec);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* EVENT2_BUFFER_H_INCLUDED_ */