1.\" $NetBSD: funopen.3,v 1.23 2015/09/06 01:36:21 dholland 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. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)funopen.3 8.1 (Berkeley) 6/9/93 33.\" 34.Dd March 16, 2012 35.Dt FUNOPEN 3 36.Os 37.Sh NAME 38.Nm funopen , 39.Nm funopen2 , 40.Nm fropen , 41.Nm fropen2 , 42.Nm fwopen , 43.Nm fwopen2 44.Nd open a stream 45.Sh LIBRARY 46.Lb libc 47.Sh SYNOPSIS 48.In stdio.h 49.Ft FILE * 50.Fn funopen "void *cookie" "int (*readfn)(void *, char *, int)" "int (*writefn)(void *, const char *, int)" "off_t (*seekfn)(void *, off_t, int)" "int (*closefn)(void *)" 51.Fn funopen2 "void *cookie" "ssize_t (*readfn)(void *, void *, size_t)" "ssize_t (*writefn)(void *, const void *, size_t)" "off_t (*seekfn)(void *, off_t, int)" "int (*flushfn)(void *)" "int (*closefn)(void *)" 52.Ft FILE * 53.Fn fropen "void *cookie" "int (*readfn)(void *, char *, int)" 54.Ft FILE * 55.Fn fropen2 "void *cookie" "ssize_t (*readfn)(void *, void *, size_t)" 56.Ft FILE * 57.Fn fwopen "void *cookie" "int (*writefn)(void *, const char *, int)" 58.Ft FILE * 59.Fn fwopen2 "void *cookie" "ssize_t (*writefn)(void *, const void *, size_t)" 60.Sh DESCRIPTION 61The 62.Fn funopen 63function 64associates a stream with up to four 65.Dq Tn I/O No functions . 66Either 67.Fa readfn 68or 69.Fa writefn 70must be specified; 71the others can be given as an appropriately-typed 72.Dv NULL 73pointer. 74These 75.Tn I/O 76functions will be used to read, write, seek and 77close the new stream. 78.Pp 79The 80.Fn funopen2 81function provides sightly different read and write signatures, which match 82better the corresponding system calls, plus the ability to augment the 83streams default flushing function. 84If a flushing function is provided, then it is called after all data has 85been written to the stream. 86.Pp 87In general, omitting a function means that any attempt to perform the 88associated operation on the resulting stream will fail. 89If the close function is omitted, closing the stream will flush 90any buffered output and then succeed. 91.Pp 92The calling conventions of 93.Fa readfn , 94.Fa writefn , 95.Fa seekfn 96and 97.Fa closefn 98must match those, respectively, of 99.Xr read 2 , 100.Xr write 2 , 101.Xr lseek 2 , 102and 103.Xr close 2 ; 104except that they are passed the 105.Fa cookie 106argument specified to 107.Fn funopen 108in place of the traditional file descriptor argument. 109.Pp 110Read and write 111.Tn I/O 112functions are allowed to change the underlying buffer 113on fully buffered or line buffered streams by calling 114.Xr setvbuf 3 . 115They are also not required to completely fill or empty the buffer. 116They are not, however, allowed to change streams from unbuffered to buffered 117or to change the state of the line buffering flag. 118They must also be prepared to have read or write calls occur on buffers other 119than the one most recently specified. 120.Pp 121All user 122.Tn I/O 123functions can report an error by returning \-1. 124Additionally, all of the functions should set the external variable 125.Va errno 126appropriately if an error occurs. 127.Pp 128An error on 129.Fn closefn 130does not keep the stream open. 131.Pp 132As a convenience, the include file 133.In stdio.h 134defines the macros 135.Fn fropen 136and 137.Fn fwopen 138as calls to 139.Fn funopen 140with only a read or write function specified. 141.Sh RETURN VALUES 142Upon successful completion, 143.Fn funopen 144returns a 145.Dv FILE 146pointer. 147Otherwise, 148.Dv NULL 149is returned and the global variable 150.Va errno 151is set to indicate the error. 152.Sh ERRORS 153.Bl -tag -width Er 154.It Bq Er EINVAL 155The 156.Fn funopen 157function 158was called without either a read or write function. 159The 160.Fn funopen 161function 162may also fail and set 163.Va errno 164for any of the errors 165specified for the routine 166.Xr malloc 3 . 167.El 168.Sh SEE ALSO 169.Xr fcntl 2 , 170.Xr open 2 , 171.Xr fclose 3 , 172.Xr fmemopen 3 , 173.Xr fopen 3 , 174.Xr fseek 3 , 175.Xr setbuf 3 176.Sh HISTORY 177The 178.Fn funopen 179functions first appeared in 180.Bx 4.4 . 181The 182.Fn funopen2 183functions first appeared in 184.Nx 7.0 . 185.Sh CAVEATS 186All three functions are specific to 187.Nx 188and thus unportable. 189