1.\" $NetBSD: funopen.3,v 1.7 1997/01/23 08:10:04 mikel Exp $ 2.\" 3.\" Copyright (c) 1990, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" This code is derived from software contributed to Berkeley by 7.\" Chris Torek. 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. All advertising materials mentioning features or use of this software 17.\" must display the following acknowledgement: 18.\" This product includes software developed by the University of 19.\" California, Berkeley and its contributors. 20.\" 4. Neither the name of the University nor the names of its contributors 21.\" may be used to endorse or promote products derived from this software 22.\" without specific prior written permission. 23.\" 24.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34.\" SUCH DAMAGE. 35.\" 36.\" @(#)funopen.3 8.1 (Berkeley) 6/9/93 37.\" 38.Dd June 9, 1993 39.Dt FUNOPEN 3 40.Os 41.Sh NAME 42.Nm funopen , 43.Nm fropen , 44.Nm fwopen 45.Nd open a stream 46.Sh SYNOPSIS 47.Fd #include <stdio.h> 48.Ft FILE * 49.Fn funopen "void *cookie" "int (*readfn)(void *, char *, int)" "int (*writefn)(void *, const char *, int)" "fpos_t (*seekfn)(void *, fpos_t, int)" "int (*closefn)(void *)" 50.Ft FILE * 51.Fn fropen "void *cookie" "int (*readfn)(void *, char *, int)" 52.Ft FILE * 53.Fn fwopen "void *cookie" "int (*writefn)(void *, const char *, int)" 54.Sh DESCRIPTION 55The 56.Fn funopen 57function 58associates a stream with up to four 59.Dq Tn I/O No functions . 60Either 61.Fa readfn 62or 63.Fa writefn 64must be specified; 65the others can be given as an appropriately-typed 66.Dv NULL 67pointer. 68These 69.Tn I/O 70functions will be used to read, write, seek and 71close the new stream. 72.Pp 73In general, omitting a function means that any attempt to perform the 74associated operation on the resulting stream will fail. 75If the close function is omitted, closing the stream will flush 76any buffered output and then succeed. 77.Pp 78The calling conventions of 79.Fa readfn , 80.Fa writefn , 81.Fa seekfn 82and 83.Fa closefn 84must match those, respectively, of 85.Xr read 2 , 86.Xr write 2 , 87.Xr lseek 2 , 88and 89.Xr close 2 ; 90except that they are passed the 91.Fa cookie 92argument specified to 93.Fn funopen 94in place of the traditional file descriptor argument, 95and 96.Fa seekfn 97uses 98.Li fpos_t 99instead of 100.Li off_t . 101.Pp 102Read and write 103.Tn I/O 104functions are allowed to change the underlying buffer 105on fully buffered or line buffered streams by calling 106.Xr setvbuf 3 . 107They are also not required to completely fill or empty the buffer. 108They are not, however, allowed to change streams from unbuffered to buffered 109or to change the state of the line buffering flag. 110They must also be prepared to have read or write calls occur on buffers other 111than the one most recently specified. 112.Pp 113All user 114.Tn I/O 115functions can report an error by returning \-1. 116Additionally, all of the functions should set the external variable 117.Va errno 118appropriately if an error occurs. 119.Pp 120An error on 121.Fn closefn 122does not keep the stream open. 123.Pp 124As a convenience, the include file 125.Aq Pa stdio.h 126defines the macros 127.Fn fropen 128and 129.Fn fwopen 130as calls to 131.Fn funopen 132with only a read or write function specified. 133.Sh RETURN VALUES 134Upon successful completion, 135.Fn funopen 136returns a 137.Dv FILE 138pointer. 139Otherwise, 140.Dv NULL 141is returned and the global variable 142.Va errno 143is set to indicate the error. 144.Sh ERRORS 145.Bl -tag -width Er 146.It Bq Er EINVAL 147The 148.Fn funopen 149function 150was called without either a read or write function. 151The 152.Fn funopen 153function 154may also fail and set 155.Va errno 156for any of the errors 157specified for the routine 158.Xr malloc 3 . 159.El 160.Sh SEE ALSO 161.Xr fcntl 2 , 162.Xr open 2 , 163.Xr fclose 3 , 164.Xr fopen 3 , 165.Xr fseek 3 , 166.Xr setbuf 3 167.Sh HISTORY 168The 169.Fn funopen 170functions first appeared in 4.4BSD. 171.Sh BUGS 172The 173.Fn funopen 174function 175may not be portable to systems other than 176.Bx . 177