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.\" $FreeBSD$ 36.\" 37.Dd March 19, 2004 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 56The 57.Fn funopen 58function 59associates a stream with up to four 60.Dq Tn I/O No functions . 61Either 62.Fa readfn 63or 64.Fa writefn 65must be specified; 66the others can be given as an appropriately-typed 67.Dv NULL 68pointer. 69These 70.Tn I/O 71functions will be used to read, write, seek and 72close the new stream. 73.Pp 74In general, omitting a function means that any attempt to perform the 75associated operation on the resulting stream will fail. 76If the close function is omitted, closing the stream will flush 77any buffered output and then succeed. 78.Pp 79The calling conventions of 80.Fa readfn , 81.Fa writefn , 82.Fa seekfn 83and 84.Fa closefn 85must match those, respectively, of 86.Xr read 2 , 87.Xr write 2 , 88.Xr lseek 2 , 89and 90.Xr close 2 91with the single exception that they are passed the 92.Fa cookie 93argument specified to 94.Fn funopen 95in place of the traditional file descriptor argument. 96.Pp 97Read and write 98.Tn I/O 99functions are allowed to change the underlying buffer 100on fully buffered or line buffered streams by calling 101.Xr setvbuf 3 . 102They are also not required to completely fill or empty the buffer. 103They are not, however, allowed to change streams from unbuffered to buffered 104or to change the state of the line buffering flag. 105They must also be prepared to have read or write calls occur on buffers other 106than the one most recently specified. 107.Pp 108All user 109.Tn I/O 110functions can report an error by returning \-1. 111Additionally, all of the functions should set the external variable 112.Va errno 113appropriately if an error occurs. 114.Pp 115An error on 116.Fn closefn 117does not keep the stream open. 118.Pp 119As a convenience, the include file 120.In stdio.h 121defines the macros 122.Fn fropen 123and 124.Fn fwopen 125as calls to 126.Fn funopen 127with only a read or write function specified. 128.Sh RETURN VALUES 129Upon successful completion, 130.Fn funopen 131returns a 132.Dv FILE 133pointer. 134Otherwise, 135.Dv NULL 136is returned and the global variable 137.Va errno 138is set to indicate the error. 139.Sh ERRORS 140.Bl -tag -width Er 141.It Bq Er EINVAL 142The 143.Fn funopen 144function 145was called without either a read or write function. 146The 147.Fn funopen 148function 149may also fail and set 150.Va errno 151for any of the errors 152specified 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 163The 164.Fn funopen 165functions first appeared in 166.Bx 4.4 . 167.Sh BUGS 168The 169.Fn funopen 170function 171may not be portable to systems other than 172.Bx . 173.Pp 174The 175.Fn funopen 176interface erroneously assumes that 177.Vt fpos_t 178is an integral type; see 179.Xr fseek 3 180for a discussion of this issue. 181