1.\" Copyright (c) 2016, EMC / Isilon Storage Division 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS 14.\" IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, 15.\" THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 16.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR 17.\" CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 18.\" EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 19.\" PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; 20.\" OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 21.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR 22.\" OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 23.\" ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24.\" 25.Dd May 9, 2016 26.Dt FOPENCOOKIE 3 27.Os 28.Sh NAME 29.Nm fopencookie 30.Nd open a stream 31.Sh LIBRARY 32.Lb libc 33.Sh SYNOPSIS 34.In stdio.h 35.Ft typedef ssize_t 36.Fn (*cookie_read_function_t) "void *cookie" "char *buf" "size_t size" 37.Ft typedef ssize_t 38.Fn (*cookie_write_function_t) "void *cookie" "const char *buf" "size_t size" 39.Ft typedef int 40.Fn (*cookie_seek_function_t) "void *cookie" "off64_t *offset" "int whence" 41.Ft typedef int 42.Fn (*cookie_close_function_t) "void *cookie" 43.Bd -literal 44typedef struct { 45 cookie_read_function_t *read; 46 cookie_write_function_t *write; 47 cookie_seek_function_t *seek; 48 cookie_close_function_t *close; 49} cookie_io_functions_t; 50.Ed 51.Ft FILE * 52.Fn fopencookie "void *cookie" "const char *mode" "cookie_io_functions_t io_funcs" 53.Sh DESCRIPTION 54The 55.Nm 56function 57associates a stream with up to four 58.Dq Tn I/O No functions . 59These 60.Tn I/O 61functions will be used to read, write, seek and 62close the new stream. 63.Pp 64In general, omitting a function means that any attempt to perform the 65associated operation on the resulting stream will fail. 66If the write function is omitted, data written to the stream is discarded. 67If the close function is omitted, closing the stream will flush 68any buffered output and then succeed. 69.Pp 70The calling conventions of 71.Fa read , 72.Fa write , 73and 74.Fa close 75must match those, respectively, of 76.Xr read 2 , 77.Xr write 2 , 78and 79.Xr close 2 80with the single exception that they are passed the 81.Fa cookie 82argument specified to 83.Nm 84in place of the traditional file descriptor argument. 85The 86.Fa seek 87function updates the current stream offset using 88.Fa *offset 89and 90.Fa whence . 91If 92.Fa *offset 93is non-NULL, it updates 94.Fa *offset 95with the current stream offset. 96.Pp 97.Nm 98is implemented as a thin shim around the 99.Xr funopen 3 100interface. 101Limitations, possibilities, and requirements of that interface apply to 102.Nm . 103.Sh RETURN VALUES 104Upon successful completion, 105.Nm 106returns a 107.Dv FILE 108pointer. 109Otherwise, 110.Dv NULL 111is returned and the global variable 112.Va errno 113is set to indicate the error. 114.Sh ERRORS 115.Bl -tag -width Er 116.It Bq Er EINVAL 117A bogus 118.Fa mode 119was provided to 120.Nm . 121.It Bq Er ENOMEM 122The 123.Nm 124function 125may fail and set 126.Va errno 127for any of the errors 128specified for the 129.Xr malloc 3 130routine. 131.El 132.Sh SEE ALSO 133.Xr fcntl 2 , 134.Xr open 2 , 135.Xr fclose 3 , 136.Xr fopen 3 , 137.Xr fseek 3 , 138.Xr funopen 3 139.Sh HISTORY 140The 141.Fn funopen 142functions first appeared in 143.Bx 4.4 . 144The 145.Nm 146function first appeared in 147.Fx 11 . 148.Sh BUGS 149The 150.Nm 151function is a nonstandard glibc extension and may not be portable to systems 152other than 153.Fx 154and Linux. 155