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. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.Dd May 9, 2016 31.Dt FUNOPEN 3 32.Os 33.Sh NAME 34.Nm funopen , 35.Nm fropen , 36.Nm fwopen 37.Nd open a stream 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In stdio.h 42.Ft FILE * 43.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 *)" 44.Ft FILE * 45.Fn fropen "void *cookie" "int (*readfn)(void *, char *, int)" 46.Ft FILE * 47.Fn fwopen "void *cookie" "int (*writefn)(void *, const char *, int)" 48.Sh DESCRIPTION 49The 50.Fn funopen 51function 52associates a stream with up to four 53.Dq Tn I/O No functions . 54Either 55.Fa readfn 56or 57.Fa writefn 58must be specified; 59the others can be given as an appropriately-typed 60.Dv NULL 61pointer. 62These 63.Tn I/O 64functions will be used to read, write, seek and 65close the new stream. 66.Pp 67In general, omitting a function means that any attempt to perform the 68associated operation on the resulting stream will fail. 69If the close function is omitted, closing the stream will flush 70any buffered output and then succeed. 71.Pp 72The calling conventions of 73.Fa readfn , 74.Fa writefn , 75.Fa seekfn 76and 77.Fa closefn 78must match those, respectively, of 79.Xr read 2 , 80.Xr write 2 , 81.Xr lseek 2 , 82and 83.Xr close 2 84with the single exception that they are passed the 85.Fa cookie 86argument specified to 87.Fn funopen 88in place of the traditional file descriptor argument. 89.Pp 90Read and write 91.Tn I/O 92functions are allowed to change the underlying buffer 93on fully buffered or line buffered streams by calling 94.Xr setvbuf 3 . 95They are also not required to completely fill or empty the buffer. 96They are not, however, allowed to change streams from unbuffered to buffered 97or to change the state of the line buffering flag. 98They must also be prepared to have read or write calls occur on buffers other 99than the one most recently specified. 100.Pp 101All user 102.Tn I/O 103functions can report an error by returning \-1. 104Additionally, all of the functions should set the external variable 105.Va errno 106appropriately if an error occurs. 107.Pp 108An error on 109.Fn closefn 110does not keep the stream open. 111.Pp 112As a convenience, the include file 113.In stdio.h 114defines the macros 115.Fn fropen 116and 117.Fn fwopen 118as calls to 119.Fn funopen 120with only a read or write function specified. 121.Sh RETURN VALUES 122Upon successful completion, 123.Fn funopen 124returns a 125.Dv FILE 126pointer. 127Otherwise, 128.Dv NULL 129is returned and the global variable 130.Va errno 131is set to indicate the error. 132.Sh ERRORS 133.Bl -tag -width Er 134.It Bq Er EINVAL 135The 136.Fn funopen 137function 138was called without either a read or write function. 139The 140.Fn funopen 141function 142may also fail and set 143.Va errno 144for any of the errors 145specified for the routine 146.Xr malloc 3 . 147.El 148.Sh SEE ALSO 149.Xr fcntl 2 , 150.Xr open 2 , 151.Xr fclose 3 , 152.Xr fopen 3 , 153.Xr fopencookie 3 , 154.Xr fseek 3 , 155.Xr setbuf 3 156.Sh HISTORY 157The 158.Fn funopen 159functions first appeared in 160.Bx 4.4 . 161.Sh BUGS 162The 163.Fn funopen 164function 165may not be portable to systems other than 166.Bx . 167.Pp 168The 169.Fn funopen 170interface erroneously assumes that 171.Vt fpos_t 172is an integral type; see 173.Xr fseek 3 174for a discussion of this issue. 175