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 1.7.2.4 2001/12/14 18:33:57 ru Exp $ 36.\" $DragonFly: src/lib/libc/stdio/funopen.3,v 1.3 2006/05/26 19:39:37 swildner Exp $ 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 LIBRARY 47.Lb libc 48.Sh SYNOPSIS 49.In stdio.h 50.Ft FILE * 51.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 *)" 52.Ft FILE * 53.Fn fropen "void *cookie" "int (*readfn)(void *, char *, int)" 54.Ft FILE * 55.Fn fwopen "void *cookie" "int (*writefn)(void *, const char *, int)" 56.Sh DESCRIPTION 57The 58.Fn funopen 59function 60associates a stream with up to four 61.Dq Tn I/O No functions . 62Either 63.Fa readfn 64or 65.Fa writefn 66must be specified; 67the others can be given as an appropriately-typed 68.Dv NULL 69pointer. 70These 71.Tn I/O 72functions will be used to read, write, seek and 73close the new stream. 74.Pp 75In general, omitting a function means that any attempt to perform the 76associated operation on the resulting stream will fail. 77If the close function is omitted, closing the stream will flush 78any buffered output and then succeed. 79.Pp 80The calling conventions of 81.Fa readfn , 82.Fa writefn , 83.Fa seekfn 84and 85.Fa closefn 86must match those, respectively, of 87.Xr read 2 , 88.Xr write 2 , 89.Xr lseek 2 , 90and 91.Xr close 2 92with the single exception that they are passed the 93.Fa cookie 94argument specified to 95.Fn funopen 96in place of the traditional file descriptor argument. 97.Pp 98Read and write 99.Tn I/O 100functions are allowed to change the underlying buffer 101on fully buffered or line buffered streams by calling 102.Xr setvbuf 3 . 103They are also not required to completely fill or empty the buffer. 104They are not, however, allowed to change streams from unbuffered to buffered 105or to change the state of the line buffering flag. 106They must also be prepared to have read or write calls occur on buffers other 107than the one most recently specified. 108.Pp 109All user 110.Tn I/O 111functions can report an error by returning \-1. 112Additionally, all of the functions should set the external variable 113.Va errno 114appropriately if an error occurs. 115.Pp 116An error on 117.Fn closefn 118does not keep the stream open. 119.Pp 120As a convenience, the include file 121.In stdio.h 122defines the macros 123.Fn fropen 124and 125.Fn fwopen 126as calls to 127.Fn funopen 128with only a read or write function specified. 129.Sh RETURN VALUES 130Upon successful completion, 131.Fn funopen 132returns a 133.Dv FILE 134pointer. 135Otherwise, 136.Dv NULL 137is returned and the global variable 138.Va errno 139is set to indicate the error. 140.Sh ERRORS 141.Bl -tag -width Er 142.It Bq Er EINVAL 143The 144.Fn funopen 145function 146was called without either a read or write function. 147The 148.Fn funopen 149function 150may also fail and set 151.Va errno 152for any of the errors 153specified for the routine 154.Xr malloc 3 . 155.El 156.Sh SEE ALSO 157.Xr fcntl 2 , 158.Xr open 2 , 159.Xr fclose 3 , 160.Xr fopen 3 , 161.Xr fseek 3 , 162.Xr setbuf 3 163.Sh HISTORY 164The 165.Fn funopen 166functions first appeared in 167.Bx 4.4 . 168.Sh BUGS 169The 170.Fn funopen 171function 172may not be portable to systems other than 173.Bx . 174