[apple/libc.git] / stdio / FreeBSD / funopen.3

.\" Copyright (c) 1990, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek.
.\" 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. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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.
.\"
.\"     @(#)funopen.3	8.1 (Berkeley) 6/9/93
.\" $FreeBSD: src/lib/libc/stdio/funopen.3,v 1.12 2001/10/01 16:08:59 ru Exp $
.\"
.Dd June 9, 1993
.Dt FUNOPEN 3
.Os
.Sh NAME
.Nm funopen ,
.Nm fropen ,
.Nm fwopen
.Nd open a stream
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdio.h
.Ft FILE *
.Fn funopen "const void *cookie" "int (*readfn)(void *, char *, int)" "int (*writefn)(void *, const char *, int)" "fpos_t (*seekfn)(void *, fpos_t, int)" "int (*closefn)(void *)"
.Ft FILE *
.Fn fropen "void  *cookie" "int  (*readfn)(void *, char *, int)"
.Ft FILE *
.Fn fwopen "void  *cookie" "int  (*writefn)(void *, const char *, int)"
.Sh DESCRIPTION
The
.Fn funopen
function
associates a stream with up to four
.Dq Tn I/O No functions .
Either
.Fa readfn
or
.Fa writefn
must be specified;
the others can be given as an appropriately-typed
.Dv NULL
pointer.
These
.Tn I/O
functions will be used to read, write, seek and
close the new stream.
.Pp
In general, omitting a function means that any attempt to perform the
associated operation on the resulting stream will fail.
If the close function is omitted, closing the stream will flush
any buffered output and then succeed.
.Pp
The calling conventions of
.Fa readfn ,
.Fa writefn ,
.Fa seekfn
and
.Fa closefn
must match those, respectively, of
.Xr read 2 ,
.Xr write 2 ,
.Xr lseek 2 ,
and
.Xr close 2
with the single exception that they are passed the
.Fa cookie
argument specified to
.Fn funopen
in place of the traditional file descriptor argument.
.Pp
Read and write
.Tn I/O
functions are allowed to change the underlying buffer
on fully buffered or line buffered streams by calling
.Xr setvbuf 3 .
They are also not required to completely fill or empty the buffer.
They are not, however, allowed to change streams from unbuffered to buffered
or to change the state of the line buffering flag.
They must also be prepared to have read or write calls occur on buffers other
than the one most recently specified.
.Pp
All user
.Tn I/O
functions can report an error by returning \-1.
Additionally, all of the functions should set the external variable
.Va errno
appropriately if an error occurs.
.Pp
An error on
.Fn closefn
does not keep the stream open.
.Pp
As a convenience, the include file
.Aq Pa stdio.h
defines the macros
.Fn fropen
and
.Fn fwopen
as calls to
.Fn funopen
with only a read or write function specified.
.Sh RETURN VALUES
Upon successful completion,
.Fn funopen
returns a
.Dv FILE
pointer.
Otherwise,
.Dv NULL
is returned and the global variable
.Va errno
is set to indicate the error.
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er EINVAL
The
.Fn funopen
function
was called without either a read or write function.
The
.Fn funopen
function
may also fail and set
.Va errno
for any of the errors
specified for the routine
.Xr malloc 3 .
.El
.Sh SEE ALSO
.Xr fcntl 2 ,
.Xr open 2 ,
.Xr fclose 3 ,
.Xr fopen 3 ,
.Xr fseek 3 ,
.Xr setbuf 3
.Sh HISTORY
The
.Fn funopen
functions first appeared in
.Bx 4.4 .
.Sh BUGS
The
.Fn funopen
function
may not be portable to systems other than
.Bx .
Commit	Line	Data
5b2abdfb A	1	.\" Copyright (c) 1990, 1991, 1993
	2	.\" The Regents of the University of California. All rights reserved.
	3	.\"
	4	.\" This code is derived from software contributed to Berkeley by
	5	.\" Chris Torek.
	6	.\" Redistribution and use in source and binary forms, with or without
	7	.\" modification, are permitted provided that the following conditions
	8	.\" are met:
	9	.\" 1. Redistributions of source code must retain the above copyright
	10	.\" notice, this list of conditions and the following disclaimer.
	11	.\" 2. Redistributions in binary form must reproduce the above copyright
	12	.\" notice, this list of conditions and the following disclaimer in the
	13	.\" documentation and/or other materials provided with the distribution.
	14	.\" 3. All advertising materials mentioning features or use of this software
	15	.\" must display the following acknowledgement:
	16	.\" This product includes software developed by the University of
	17	.\" California, Berkeley and its contributors.
	18	.\" 4. Neither the name of the University nor the names of its contributors
	19	.\" may be used to endorse or promote products derived from this software
	20	.\" without specific prior written permission.
	21	.\"
	22	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	23	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	24	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	25	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	26	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	27	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	28	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	29	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	30	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	31	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	32	.\" SUCH DAMAGE.
	33	.\"
	34	.\" @(#)funopen.3 8.1 (Berkeley) 6/9/93
	35	.\" $FreeBSD: src/lib/libc/stdio/funopen.3,v 1.12 2001/10/01 16:08:59 ru Exp $
	36	.\"
	37	.Dd June 9, 1993
	38	.Dt FUNOPEN 3
	39	.Os
	40	.Sh NAME
	41	.Nm funopen ,
	42	.Nm fropen ,
	43	.Nm fwopen
	44	.Nd open a stream
	45	.Sh LIBRARY
	46	.Lb libc
	47	.Sh SYNOPSIS
	48	.In stdio.h
	49	.Ft FILE *
	50	.Fn funopen "const void cookie" "int (readfn)(void , char , int)" "int (writefn)(void , const char , int)" "fpos_t (seekfn)(void , fpos_t, int)" "int (closefn)(void *)"
	51	.Ft FILE *
	52	.Fn fropen "void cookie" "int (readfn)(void , char , int)"
	53	.Ft FILE *
	54	.Fn fwopen "void cookie" "int (writefn)(void , const char , int)"
	55	.Sh DESCRIPTION
	56	The
	57	.Fn funopen
	58	function
	59	associates a stream with up to four
	60	.Dq Tn I/O No functions .
	61	Either
	62	.Fa readfn
	63	or
	64	.Fa writefn
65	must be specified;
66	the others can be given as an appropriately-typed
67	.Dv NULL
68	pointer.
69	These
70	.Tn I/O
71	functions will be used to read, write, seek and
72	close the new stream.
73	.Pp
74	In general, omitting a function means that any attempt to perform the
75	associated operation on the resulting stream will fail.
76	If the close function is omitted, closing the stream will flush
77	any buffered output and then succeed.
78	.Pp
79	The calling conventions of
80	.Fa readfn ,
81	.Fa writefn ,
82	.Fa seekfn
83	and
84	.Fa closefn
85	must match those, respectively, of
86	.Xr read 2 ,
87	.Xr write 2 ,
88	.Xr lseek 2 ,
89	and
90	.Xr close 2
91	with the single exception that they are passed the
92	.Fa cookie
93	argument specified to
94	.Fn funopen
95	in place of the traditional file descriptor argument.
96	.Pp
97	Read and write
98	.Tn I/O
99	functions are allowed to change the underlying buffer
100	on fully buffered or line buffered streams by calling
101	.Xr setvbuf 3 .
102	They are also not required to completely fill or empty the buffer.
103	They are not, however, allowed to change streams from unbuffered to buffered
104	or to change the state of the line buffering flag.
105	They must also be prepared to have read or write calls occur on buffers other
106	than the one most recently specified.
107	.Pp
108	All user
109	.Tn I/O
110	functions can report an error by returning \-1.
111	Additionally, all of the functions should set the external variable
112	.Va errno
113	appropriately if an error occurs.
114	.Pp
115	An error on
116	.Fn closefn
117	does not keep the stream open.
118	.Pp
119	As a convenience, the include file
120	.Aq Pa stdio.h
121	defines the macros
122	.Fn fropen
123	and
124	.Fn fwopen
125	as calls to
126	.Fn funopen
127	with only a read or write function specified.
128	.Sh RETURN VALUES
129	Upon successful completion,
130	.Fn funopen
131	returns a
132	.Dv FILE
133	pointer.
134	Otherwise,
135	.Dv NULL
136	is returned and the global variable
137	.Va errno
138	is set to indicate the error.
139	.Sh ERRORS
140	.Bl -tag -width Er
141	.It Bq Er EINVAL
142	The
143	.Fn funopen
144	function
145	was called without either a read or write function.
146	The
147	.Fn funopen
148	function
149	may also fail and set
150	.Va errno
151	for any of the errors
152	specified for the routine
153	.Xr malloc 3 .
154	.El
155	.Sh SEE ALSO
156	.Xr fcntl 2 ,
157	.Xr open 2 ,
158	.Xr fclose 3 ,
159	.Xr fopen 3 ,
160	.Xr fseek 3 ,
161	.Xr setbuf 3
162	.Sh HISTORY
163	The
164	.Fn funopen
165	functions first appeared in
166	.Bx 4.4 .
167	.Sh BUGS
168	The
169	.Fn funopen
170	function
171	may not be portable to systems other than
172	.Bx .