1.\" $OpenBSD: funopen.3,v 1.14 2007/05/31 19:19:31 jmc 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.Dd $Mdocdate: May 31 2007 $ 33.Dt FUNOPEN 3 34.Os 35.Sh NAME 36.Nm funopen , 37.Nm fropen , 38.Nm fwopen 39.Nd open a stream 40.Sh SYNOPSIS 41.Fd #include <stdio.h> 42.Ft FILE * 43.Fn funopen "const void *cookie" "int (*readfn)(void *, char *, int)" \ 44 "int (*writefn)(void *, const char *, int)" \ 45 "fpos_t (*seekfn)(void *, fpos_t, int)" \ 46 "int (*closefn)(void *)" 47.Ft FILE * 48.Fn fropen "const void *cookie" "int (*readfn)(void *, char *, int)" 49.Ft FILE * 50.Fn fwopen "const void *cookie" "int (*writefn)(void *, const char *, int)" 51.Sh DESCRIPTION 52The 53.Fn funopen 54function associates a stream with up to four 55.Dq Tn I/O No functions . 56Either 57.Fa readfn 58or 59.Fa writefn 60must be specified; 61the others may be given as 62.Dv NULL 63pointers. 64These 65.Tn I/O 66functions will be used to read, write, seek, and close the new stream. 67.Pp 68In general, omitting a function means that any attempt to perform the 69associated operation on the resulting stream will fail. 70If the close function is omitted, closing the stream will flush 71any buffered output and then succeed. 72.Pp 73The calling conventions of 74.Fa readfn , 75.Fa writefn , 76.Fa seekfn , 77and 78.Fa closefn 79must match those, respectively, of 80.Xr read 2 , 81.Xr write 2 , 82.Xr lseek 2 , 83and 84.Xr close 2 85with the exceptions that they are passed the 86.Fa cookie 87argument specified to 88.Fn funopen 89in place of the traditional file descriptor argument and that 90the seek function takes an 91.Li fpos_t 92argument and not an 93.Li off_t 94argument. 95.Pp 96Read and write 97.Tn I/O 98functions are allowed to change the underlying buffer 99on fully buffered or line buffered streams by calling 100.Xr setvbuf 3 . 101They are also not required to completely fill or empty the buffer. 102They are not, however, allowed to change streams from unbuffered to buffered 103or to change the state of the line buffering flag. 104They must also be prepared to have read or write calls occur on buffers other 105than the one most recently specified. 106.Pp 107All user 108.Tn I/O 109functions can report an error by returning \-1. 110Additionally, all of the functions should set the external variable 111.Va errno 112appropriately if an error occurs. 113.Pp 114An error on 115.Fn closefn 116does not keep the stream open. 117.Pp 118As a convenience, the include file 119.Aq Pa stdio.h 120defines the macros 121.Fn fropen 122and 123.Fn fwopen 124as calls to 125.Fn funopen 126with only a read or write function specified. 127.Sh RETURN VALUES 128Upon successful completion, 129.Fn funopen 130returns a 131.Dv FILE 132pointer. 133Otherwise, 134.Dv NULL 135is returned and the global variable 136.Va errno 137is set to indicate the error. 138.Sh ERRORS 139.Bl -tag -width Er 140.It Bq Er EINVAL 141The 142.Fn funopen 143function was called without either a read or write function. 144The 145.Fn funopen 146function may also fail and set 147.Va errno 148for any of the errors specified for the routine 149.Xr malloc 3 . 150.El 151.Sh SEE ALSO 152.Xr fcntl 2 , 153.Xr open 2 , 154.Xr fclose 3 , 155.Xr fopen 3 , 156.Xr fseek 3 , 157.Xr setbuf 3 158.Sh HISTORY 159The 160.Fn funopen 161functions first appeared in 162.Bx 4.4 . 163.Sh BUGS 164The 165.Fn funopen 166function may not be portable to systems other than 167.Bx . 168