.\" $OpenBSD: ibuf_add.3,v 1.12 2025/06/13 18:34:00 schwarze Exp $
.\"
.\" Copyright (c) 2023 Claudio Jeker <claudio@openbsd.org>
.\" Copyright (c) 2010 Nicholas Marriott <nicm@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
.\" IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
.\" OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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.Dd $Mdocdate: June 13 2025 $
.Dt IBUF_ADD 3
.Os
.Sh NAME
.Nm ibuf_add ,
.Nm ibuf_add_h16 ,
.Nm ibuf_add_h32 ,
.Nm ibuf_add_h64 ,
.Nm ibuf_add_ibuf ,
.Nm ibuf_add_n16 ,
.Nm ibuf_add_n32 ,
.Nm ibuf_add_n64 ,
.Nm ibuf_add_n8 ,
.Nm ibuf_add_strbuf ,
.Nm ibuf_add_zero ,
.Nm ibuf_close ,
.Nm ibuf_data ,
.Nm ibuf_dynamic ,
.Nm ibuf_fd_avail ,
.Nm ibuf_fd_get ,
.Nm ibuf_fd_set ,
.Nm ibuf_free ,
.Nm ibuf_from_buffer ,
.Nm ibuf_from_ibuf ,
.Nm ibuf_get ,
.Nm ibuf_get_ibuf ,
.Nm ibuf_get_h16 ,
.Nm ibuf_get_h32 ,
.Nm ibuf_get_h64 ,
.Nm ibuf_get_n16 ,
.Nm ibuf_get_n32 ,
.Nm ibuf_get_n64 ,
.Nm ibuf_get_n8 ,
.Nm ibuf_get_strbuf ,
.Nm ibuf_get_string ,
.Nm ibuf_left ,
.Nm ibuf_open ,
.Nm ibuf_read ,
.Nm ibuf_reserve ,
.Nm ibuf_rewind ,
.Nm ibuf_seek ,
.Nm ibuf_set ,
.Nm ibuf_set_h16 ,
.Nm ibuf_set_h32 ,
.Nm ibuf_set_h64 ,
.Nm ibuf_set_n16 ,
.Nm ibuf_set_n32 ,
.Nm ibuf_set_n64 ,
.Nm ibuf_set_n8 ,
.Nm ibuf_set_maxsize ,
.Nm ibuf_size ,
.Nm ibuf_skip ,
.Nm ibuf_truncate ,
.Nm ibuf_write ,
.Nm msgbuf_clear ,
.Nm msgbuf_concat ,
.Nm msgbuf_free ,
.Nm msgbuf_get ,
.Nm msgbuf_new ,
.Nm msgbuf_new_reader ,
.Nm msgbuf_queuelen ,
.Nm msgbuf_read ,
.Nm msgbuf_write ,
.Nm ibufq_concat ,
.Nm ibufq_flush ,
.Nm ibufq_free ,
.Nm ibufq_new ,
.Nm ibufq_pop ,
.Nm ibufq_push ,
.Nm ibufq_queuelen
.Nd save buffer API for basic IO
.Sh SYNOPSIS
.Lb libutil
.In imsg.h
.Fd #define IBUF_READ_SIZE 65535
.Ft int
.Fn ibuf_add "struct ibuf *buf" "const void *data" "size_t len"
.Ft int
.Fn ibuf_add_h16 "struct ibuf *buf" "uint64_t value"
.Ft int
.Fn ibuf_add_h32 "struct ibuf *buf" "uint64_t value"
.Ft int
.Fn ibuf_add_h64 "struct ibuf *buf" "uint64_t value"
.Ft int
.Fn ibuf_add_ibuf "struct ibuf *buf" "const struct ibuf *from"
.Ft int
.Fn ibuf_add_n16 "struct ibuf *buf" "uint64_t value"
.Ft int
.Fn ibuf_add_n32 "struct ibuf *buf" "uint64_t value"
.Ft int
.Fn ibuf_add_n64 "struct ibuf *buf" "uint64_t value"
.Ft int
.Fn ibuf_add_n8 "struct ibuf *buf" "uint64_t value"
.Ft int
.Fn ibuf_add_strbuf "struct ibuf *buf" "const char *str" "size_t len"
.Ft int
.Fn ibuf_add_zero "struct ibuf *buf" "size_t len"
.Ft void
.Fn ibuf_close "struct msgbuf *msgbuf" "struct ibuf *buf"
.Ft void *
.Fn ibuf_data "struct ibuf *buf"
.Ft struct ibuf *
.Fn ibuf_dynamic "size_t len" "size_t max"
.Ft int
.Fn ibuf_fd_avail "struct ibuf *buf"
.Ft int
.Fn ibuf_fd_get "struct ibuf *buf"
.Ft void
.Fn ibuf_fd_set "struct ibuf *buf" "int fd"
.Ft void
.Fn ibuf_free "struct ibuf *buf"
.Ft void
.Fn ibuf_from_buffer "struct ibuf *buf" "void *data" "size_t len"
.Ft void
.Fn ibuf_from_ibuf "struct ibuf *buf" "const ibuf *from"
.Ft int
.Fn ibuf_get "struct ibuf *buf" "void *data" "size_t len"
.Ft int
.Fn ibuf_get_ibuf "struct ibuf *buf" "size_t len" "struct ibuf *new"
.Ft int
.Fn ibuf_get_h16 "struct ibuf *buf" "uint16_t *value"
.Ft int
.Fn ibuf_get_h32 "struct ibuf *buf" "uint32_t *value"
.Ft int
.Fn ibuf_get_h64 "struct ibuf *buf" "uint64_t *value"
.Ft int
.Fn ibuf_get_n16 "struct ibuf *buf" "uint16_t *value"
.Ft int
.Fn ibuf_get_n32 "struct ibuf *buf" "uint32_t *value"
.Ft int
.Fn ibuf_get_n64 "struct ibuf *buf" "uint64_t *value"
.Ft int
.Fn ibuf_get_n8 "struct ibuf *buf" "uint8_t *value"
.Ft int
.Fn ibuf_get_strbuf "struct ibuf *buf" "char *str" "size_t len"
.Ft char *
.Fn ibuf_get_string "struct ibuf *buf" "size_t len"
.Ft size_t
.Fn ibuf_left "const struct ibuf *buf"
.Ft struct ibuf *
.Fn ibuf_open "size_t len"
.Ft int
.Fn ibuf_read "int fd" "struct msgbuf *msgbuf"
.Ft void *
.Fn ibuf_reserve "struct ibuf *buf" "size_t len"
.Ft void
.Fn ibuf_rewind "struct ibuf *buf"
.Ft void *
.Fn ibuf_seek "struct ibuf *buf" "size_t pos" "size_t len"
.Ft int
.Fn ibuf_set "struct ibuf *buf" "size_t pos" "const void *data" \
    "size_t len"
.Ft int
.Fn ibuf_set_h16 "struct ibuf *buf" "size_t pos" "uint64_t value"
.Ft int
.Fn ibuf_set_h32 "struct ibuf *buf" "size_t pos" "uint64_t value"
.Ft int
.Fn ibuf_set_h64 "struct ibuf *buf" "size_t pos" "uint64_t value"
.Ft int
.Fn ibuf_set_n16 "struct ibuf *buf" "size_t pos" "uint64_t value"
.Ft int
.Fn ibuf_set_n32 "struct ibuf *buf" "size_t pos" "uint64_t value"
.Ft int
.Fn ibuf_set_n64 "struct ibuf *buf" "size_t pos" "uint64_t value"
.Ft int
.Fn ibuf_set_n8 "struct ibuf *buf" "size_t pos" "uint64_t value"
.Ft int
.Fn ibuf_set_maxsize "struct ibuf *buf" "size_t max"
.Ft size_t
.Fn ibuf_size "const struct ibuf *buf"
.Ft int
.Fn ibuf_skip "struct ibuf *buf" "size_t len"
.Ft int
.Fn ibuf_truncate "struct ibuf *buf" "size_t len"
.Ft int
.Fn ibuf_write "int fd" "struct msgbuf *msgbuf"
.Ft void
.Fn msgbuf_clear "struct msgbuf *msgbuf"
.Ft void
.Fn msgbuf_concat "struct msgbuf *msgbuf" "struct ibufqueue *from"
.Ft void
.Fn msgbuf_free "struct msgbuf *msgbuf"
.Ft struct ibuf *
.Fn msgbuf_get "struct msgbuf *msgbuf"
.Ft struct msgbuf *
.Fn msgbuf_new void
.Ft struct msgbuf *
.Fn msgbuf_new_reader "size_t hdrsz" \
    "struct ibuf *(*readhdr)(struct ibuf *, void *, int *)" "void *arg"
.Ft uint32_t
.Fn msgbuf_queuelen "struct msgbuf *msgbuf"
.Ft int
.Fn msgbuf_read "int fd" "struct msgbuf *msgbuf"
.Ft int
.Fn msgbuf_write "int fd" "struct msgbuf *msgbuf"
.Ft void
.Fn ibufq_concat "struct ibufqueue *to" "struct ibufqueue *from"
.Ft void
.Fn ibufq_flush "struct ibufqueue *bufq"
.Ft void
.Fn ibufq_free "struct ibufqueue *bufq"
.Ft struct ibufqueue *
.Fn ibufq_new void
.Ft struct ibuf *
.Fn ibufq_pop "struct ibufqueue *bufq"
.Ft void
.Fn ibufq_push "struct ibufqueue *bufq" "struct ibuf *buf"
.Ft uint32_t
.Fn ibufq_queuelen "struct ibufqueue *bufq"
.Sh DESCRIPTION
The ibuf API defines functions to manipulate buffers, used for example to
construct imsgs with
.Xr imsg_create 3 .
A
.Vt struct ibuf
is a single buffer.
It has a maximum size, a read and a write position.
Buffers should be either constructed with the various
.Fn ibuf_add
and
.Fn ibuf_set
functions or consumed with the various
.Fn ibuf_get
functions.
A
.Vt struct msgbuf
is used to queue the output buffers for transmission.
.Pp
.Fn ibuf_add
appends a block of data to
.Fa buf .
0 is returned on success and \-1 on failure.
.Pp
.Fn ibuf_add_h16 ,
.Fn ibuf_add_h32 ,
and
.Fn ibuf_add_h64
add a 2-byte, 4-byte, and 8-byte
.Fa value
to
.Fa buf
in host byte order.
This function checks
.Fa value
to not overflow.
0 is returned on success and \-1 on failure.
.Pp
.Fn ibuf_add_ibuf
appends the buffer
.Fa from
to
.Fa buf .
0 is returned on success and \-1 on failure.
.Pp
.Fn ibuf_add_n8 ,
.Fn ibuf_add_n16 ,
.Fn ibuf_add_n32 ,
and
.Fn ibuf_add_n64
add a 1-byte, 2-byte, 4-byte, and 8-byte
.Fa value
to
.Fa buf
in network byte order.
This function checks
.Fa value
to not overflow.
0 is returned on success and \-1 on failure.
.Pp
.Fn ibuf_add_strbuf
appends a fixed-size buffer containing a string,
zero-padded to
.Fa len ,
which must be large enough to allow at least one NUL.
0 is returned on success and \-1 on failure.
.Pp
.Fn ibuf_add_zero
appends a block of zeros to
.Fa buf .
0 is returned on success and \-1 on failure.
.Pp
.Fn ibuf_close
appends
.Fa buf
to
.Fa msgbuf
ready to be sent.
.Pp
.Fn ibuf_data
returns the pointer to the internal buffer.
This function should only be used together with
.Fn ibuf_size
to process a previously generated buffer.
.Pp
.Fn ibuf_dynamic
allocates a resizeable buffer of initial length
.Fa len
and maximum size
.Fa max .
Buffers allocated with
.Fn ibuf_dynamic
are automatically grown if necessary when data is added.
.Pp
.Fn ibuf_fd_avail ,
.Fn ibuf_fd_get
and
.Fn ibuf_fd_set
are functions to check, get and set the file descriptor assigned to
.Fa buf .
After calling
.Fn ibuf_fd_set
the file descriptor is part of the
.Fa buf
and will be transmitted or closed by the ibuf API.
Any previously set file descriptor will be closed before assigning a
new descriptor.
.Fn ibuf_fd_get
returns the file descriptor and passes the responsibility to track the
descriptor back to the program.
.Fn ibuf_fd_avail
returns true if there is a file descriptor set on
.Fa buf .
.Pp
.Fn ibuf_free
frees
.Fa buf
and any associated storage, and closes any file descriptor set with
.Fn ibuf_fd_set .
If
.Fa buf
is a NULL pointer, no action occurs.
.Pp
.Fn ibuf_from_buffer
initializes the passed
.Fa buf
to point at
.Fa data
and spanning
.Fa len
bytes.
The returned buffer can be read using the various
.Fn ibuf_get
functions.
.Fn ibuf_from_ibuf
duplicates the
.Fa from
ibuf into
.Fa buf
without modifying
.Fa from .
This allows safely peeking into an ibuf without consuming data.
.Pp
.Fn ibuf_get
consumes a block of data from
.Fa buf
spanning
.Fa len
bytes.
0 is returned on success and \-1 on failure.
.Pp
.Fn ibuf_get_ibuf
consumes
.Fa len
bytes from the buffer
.Fa buf
and returns it in
.Fa new
covering this region.
The data in this buffer is only valid as long as
.Fa buf
remains valid.
There is no need to deallocate
.Fa new
using
.Fn ibuf_free .
0 is returned on success and \-1 on failure.
.Pp
.Fn ibuf_get_h16 ,
.Fn ibuf_get_h32 ,
and
.Fn ibuf_get_h64
get a 2-byte, 4-byte, and 8-byte
.Fa value
from
.Fa buf
without altering byte order.
0 is returned on success and \-1 on failure.
.Pp
.Fn ibuf_get_n8 ,
.Fn ibuf_get_n16 ,
.Fn ibuf_get_n32 ,
and
.Fn ibuf_get_n64
get a 1-byte, 2-byte, 4-byte, and 8-byte
.Fa value
from
.Fa buf
converting the value from network to host byte order.
0 is returned on success and \-1 on failure.
.Pp
.Fn ibuf_get_strbuf
copies
.Fa len
bytes from the buffer
.Fa buf
into
.Fa str ,
ensuring that it is NUL-terminated.
0 is returned on success and \-1 on failure.
.Pp
.Fn ibuf_get_string
consumes
.Fa len
bytes from the buffer
.Fa buf
and returns the result of passing the bytes and len to
.Xr strndup 3 .
The returned pointer should be passed to
.Xr free 3
when it is no longer needed.
On error NULL is returned.
.Pp
The
.Fn ibuf_open
function allocates a fixed-length buffer.
The buffer may not be resized and may contain a maximum of
.Fa len
bytes.
On success
.Fn ibuf_open
returns a pointer to the buffer; on failure it returns NULL.
.Pp
The
.Fn ibuf_read
routine receives pending messages using
.Xr read 2 .
It calls the
.Fn readhdr
callback to obtain a
.Vt struct ibuf
of the appropriate size.
It returns 1 on success, 0 if the connection was closed and \-1 on error
and the global variable errno is set to indicate the error.
The errors
.Er EINTR
and
.Er EAGAIN
are treated as follows:
.Er EINTR
will automatically retry the read operation while
.Er EAGAIN
will be ignored with a 1 return.
The application will then retry the operation at a later stage.
.Pp
.Fn ibuf_reserve
is used to reserve
.Fa len
bytes in
.Fa buf .
A pointer to the start of the reserved space is returned, or NULL on error.
.Pp
.Fn ibuf_rewind
resets the read offset to the start of the buffer.
.Pp
.Fn ibuf_seek
returns a pointer to the part of the buffer at offset
.Fa pos
and of extent
.Fa len .
NULL is returned if the requested range is outside the part of the buffer
in use.
.Pp
.Fn ibuf_set
replaces a part of
.Fa buf
at offset
.Fa pos
with the
.Fa data
of extent
.Fa len .
0 is returned on success and \-1 on failure.
.Pp
.Fn ibuf_set_h16 ,
.Fn ibuf_set_h32
and
.Fn ibuf_set_h64
replace a 2-byte, 4-byte or 8-byte
.Fa value
at offset
.Fa pos
in the buffer
.Fa buf
in host byte order.
This function checks
.Fa value
to not overflow.
0 is returned on success and \-1 on failure.
.Pp
.Fn ibuf_set_n8 ,
.Fn ibuf_set_n16 ,
.Fn ibuf_set_n32
and
.Fn ibuf_set_n64
replace a 1-byte, 2-byte, 4-byte or 8-byte
.Fa value
at offset
.Fa pos
in the buffer
.Fa buf
in network byte order.
This function checks
.Fa value
to not overflow.
0 is returned on success and \-1 on failure.
.Pp
.Fn ibuf_set_maxsize
reduces the maximum payload of
.Fa buf
to
.Fa max .
0 is returned on success and \-1 on failure.
.Pp
.Fn ibuf_size
and
.Fn ibuf_left
are functions which return the total bytes used and available in
.Fa buf ,
respectively.
.Pp
.Fn ibuf_skip
advances the read position in
.Fa buf
by
.Fa len
bytes.
0 is returned on success and \-1 on failure.
.Pp
.Fn ibuf_truncate
truncates the buffer to
.Fa len
bytes if necessary zero extending the buffer.
0 is returned on success and \-1 on failure.
.Pp
The
.Fn ibuf_write
routine transmits as many pending buffers as possible from
.Fa msgbuf
using
.Xr writev 2 .
It returns 0 if it succeeds, -1 on error and the global variable
.Va errno
is set to indicate the error.
The errors
.Er EINTR ,
.Er EAGAIN ,
and
.Er ENOBUFS
are treated as follows:
.Er EINTR
will automatically retry the write operation while the other errors are
ignored with a 0 return.
The application will then retry the operation at a later stage.
.Pp
.Fn msgbuf_clear
empties a msgbuf, removing and discarding any queued buffers.
.Pp
.Fn msgbuf_concat
moves all queued buffers from the ibufqueue
.Fa from
to the msgbuf.
Afterwards the ibufqueue
.Fa from
is empty.
.Pp
.Fn msgbuf_free
function frees the
.Fa msgbuf
allocated by
.Fn msgbuf_new
or
.Fn msgbuf_new_reader .
.Fn msgbuf_get
returns the next pending message.
It should be called in a loop until NULL is returned.
The ibuf returned must be freed by calling
.Fa ibuf_free .
.Pp
.Fn msgbuf_new
allocates a new message buffer structure which can be used with
.Fn ibuf_write
or
.Fn msbuf_write .
On error NULL is returned.
.Pp
.Fn msgbuf_new_reader
allocates a new message buffer structure which can additionally be used with
.Fn ibuf_read
and
.Fn msgbuf_read .
The
.Fa hdrsz
argument defines the size of the ibuf passed to the
.Fa readhdr
callback.
The
.Fa readhdr
callback parses the header and returns a new
.Vt struct ibuf
of the size of the full message.
It can take ownership of the file descriptor passed in its
.Vt "int *"
argument.
It should return NULL on error and set the global variable
.Va errno
appropriately.
The
.Fa arg
pointer is passed to the
.Fa readhdr
callback.
On error
.Fn msgbuf_new_reader
returns NULL.
.Pp
.Fn msgbuf_queuelen
returns the number of messages queued in
.Fa msgbuf .
This function returns 0 if no messages are pending for transmission.
.Pp
The
.Fn msgbuf_read
routine receives pending messages using
.Xr recvmsg 2 and supports file descriptor passing.
The function calls the
.Fn readhdr
callback function to get the total size of message.
It returns 1 on success, 0 if the connection was closed and \-1 on error
and the global variable errno is set to indicate the error.
The errors
.Er EINTR
and
.Er EAGAIN
are treated as follows:
.Er EINTR
will automatically retry the read operation while
.Er EAGAIN
will be ignored with a 1 return.
The application will then retry the operation at a later stage.
.Pp
The
.Fn msgbuf_write
routine calls
.Xr sendmsg 2
to transmit buffers queued in
.Fa msgbuf
and supports file descriptor passing.
It returns 0 if it succeeds, -1 on error and the global variable
.Va errno
is set to indicate the error.
The errors
.Er EINTR ,
.Er EAGAIN ,
and
.Er ENOBUFS
are treated as follows:
.Er EINTR
will automatically retry the write operation while the other errors are
ignored with a 0 return.
The application will then retry the operation at a later stage.
.Pp
The ibufqueue API can be used to implement additional buffer queues.
This can be useful in multithreaded applications to pass ibufs between
different threads.
.Pp
.Fn ibufq_new
allocates a new ibufqueue.
On error NULL is returned.
.Pp
.Fn ibufq_free
frees a previously allocated ibufqueue.
All queued ibufs are flushed before.
.Pp
.Fn ibufq_flush
frees any queued buffer.
.Pp
.Fn ibufq_push
and
.Fn ibufq_pop
queue and dequeue ibufs onto the ibufqueue
.Fa bufq .
.Pp
.Fn ibufq_queuelen
returns the number of buffers enqueued on
.Fa bufq .
.Pp
.Fn ibufq_concat
moves all buffers from
.Fa from
to
.Fa to .
.Sh SEE ALSO
.Xr socketpair 2 ,
.Xr imsg_add 3 ,
.Xr unix 4