1.\" Copyright (c) 1990, 1991 The Regents of the University of California. 2.\" 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 5.3 (Berkeley) 4/19/91 35.\" 36.Dd April 19, 1991 37.Dt FUNOPEN 3 38.Os 39.Sh NAME 40.Nm funopen , 41.Nm fropen , 42.Nm fwopen 43.Nd open a stream 44.Sh SYNOPSIS 45.Fd #include <stdio.h> 46.Ft FILE * 47.Fn funopen "void *cookie" "int (*readfn)(void *, char *, int)" "int (writefn*)(void *, const char *, int)" "fpos_t (seekfn*)(void *, fpos_t, int)" "int (closefn*)(void *)" 48.Ft FILE * 49.Fn fropen "void *cookie" "int (*readfn)(void *, char *, int)" 50.Ft FILE * 51.Fn fwopen "void *cookie" "int (*writefn)(void *, char *, int)" 52.Sh DESCRIPTION 53The 54.Fn funopen 55function 56associates a stream with up to four 57.Dq Tn I/O No functions . 58Either 59.Fa readfn 60or 61.Fa writefn 62must be specified; 63the others can be given as an appropriately-typed 64.Dv NULL 65pointer. 66These 67.Tn I/O 68functions will be used to read, write, seek and 69close the new stream. 70.Pp 71In general, omitting a function means that any attempt to perform the 72associated operation on the resulting stream will fail. 73If the close function is omitted, closing the stream will flush 74any buffered output and then succeed. 75.Pp 76The calling conventions of 77.Fa readfn , 78.Fa writefn , 79.Fa seekfn 80and 81.Fa closefn 82must match those, respectively, of 83.Xr read 2 , 84.Xr write 2 , 85.Xr seek 2 , 86and 87.Xr close 2 88with the single exception that they are passed the 89.Fa cookie 90argument specified to 91.Fn funopen 92in place of the traditional file descriptor argument. 93.Pp 94Read and write 95.Tn I/O 96functions are allowed to change the underlying buffer 97on fully buffered or line buffered streams by calling 98.Xr setvbuf 3 . 99They are also not required to completely fill or empty the buffer. 100They are not, however, allowed to change streams from unbuffered to buffered 101or to change the state of the line buffering flag. 102They must also be prepared to have read or write calls occur on buffers other 103than the one most recently specified. 104.Pp 105All user 106.Tn I/O 107functions can report an error by returning \-1. 108Additionally, all of the functions should set the external variable 109.Va errno 110appropriately if an error occurs. 111.Pp 112An error on 113.Fn closefn 114does not keep the stream open. 115.Pp 116As a convenience, the include file 117.Aq Pa stdio.h 118defines the macros 119.Fn fropen 120and 121.Fn fwopen 122as calls to 123.Fn funopen 124with only a read or write function specified. 125.Sh RETURN VALUES 126Upon successful completion, 127.Fn funopen 128returns a 129.Dv FILE 130pointer. 131Otherwise, 132.Dv NULL 133is returned and the global variable 134.Va errno 135is set to indicate the error. 136.Sh ERRORS 137.Bl -tag -width [EINVAL] 138.It Bq Er EINVAL 139The 140.Fn funopen 141function 142was called without either a read or write function. 143The 144.Fn funopen 145function 146may also fail and set 147.Va errno 148for any of the errors 149specified for the routine 150.Xr malloc 3 . 151.El 152.Sh SEE ALSO 153.Xr fcntl 2 , 154.Xr open 2 , 155.Xr fclose 3 , 156.Xr fopen 3 , 157.Xr fseek 3 , 158.Xr setbuf 3 159.Sh HISTORY 160These 161functions are 162.Ud . 163.Sh BUGS 164The 165.Fn funopen 166function 167may not be portable to systems other than 168.Bx . 169