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 49 The 50 .Fn funopen 51 function 52 associates a stream with up to four 53 .Dq Tn I/O No functions . 54 Either 55 .Fa readfn 56 or 57 .Fa writefn 58 must be specified; 59 the others can be given as an appropriately-typed 60 .Dv NULL 61 pointer. 62 These 63 .Tn I/O 64 functions will be used to read, write, seek and 65 close the new stream. 66 .Pp 67 In general, omitting a function means that any attempt to perform the 68 associated operation on the resulting stream will fail. 69 If the close function is omitted, closing the stream will flush 70 any buffered output and then succeed. 71 .Pp 72 The calling conventions of 73 .Fa readfn , 74 .Fa writefn , 75 .Fa seekfn 76 and 77 .Fa closefn 78 must match those, respectively, of 79 .Xr read 2 , 80 .Xr write 2 , 81 .Xr lseek 2 , 82 and 83 .Xr close 2 84 with the single exception that they are passed the 85 .Fa cookie 86 argument specified to 87 .Fn funopen 88 in place of the traditional file descriptor argument. 89 .Pp 90 Read and write 91 .Tn I/O 92 functions are allowed to change the underlying buffer 93 on fully buffered or line buffered streams by calling 94 .Xr setvbuf 3 . 95 They are also not required to completely fill or empty the buffer. 96 They are not, however, allowed to change streams from unbuffered to buffered 97 or to change the state of the line buffering flag. 98 They must also be prepared to have read or write calls occur on buffers other 99 than the one most recently specified. 100 .Pp 101 All user 102 .Tn I/O 103 functions can report an error by returning \-1. 104 Additionally, all of the functions should set the external variable 105 .Va errno 106 appropriately if an error occurs. 107 .Pp 108 An error on 109 .Fn closefn 110 does not keep the stream open. 111 .Pp 112 As a convenience, the include file 113 .In stdio.h 114 defines the macros 115 .Fn fropen 116 and 117 .Fn fwopen 118 as calls to 119 .Fn funopen 120 with only a read or write function specified. 121 .Sh RETURN VALUES 122 Upon successful completion, 123 .Fn funopen 124 returns a 125 .Dv FILE 126 pointer. 127 Otherwise, 128 .Dv NULL 129 is returned and the global variable 130 .Va errno 131 is set to indicate the error. 132 .Sh ERRORS 133 .Bl -tag -width Er 134 .It Bq Er EINVAL 135 The 136 .Fn funopen 137 function 138 was called without either a read or write function. 139 The 140 .Fn funopen 141 function 142 may also fail and set 143 .Va errno 144 for any of the errors 145 specified 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 157 The 158 .Fn funopen 159 functions first appeared in 160 .Bx 4.4 . 161 .Sh BUGS 162 The 163 .Fn funopen 164 function 165 may not be portable to systems other than 166 .Bx . 167 .Pp 168 The 169 .Fn funopen 170 interface erroneously assumes that 171 .Vt fpos_t 172 is an integral type; see 173 .Xr fseek 3 174 for a discussion of this issue. 175