| 1 | .\" Copyright (c) 1990 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 | .\" |
| 7 | .\" %sccs.include.redist.man% |
| 8 | .\" |
| 9 | .\" @(#)funopen.3 5.1 (Berkeley) %G% |
| 10 | .\" |
| 11 | .TH FUNOPEN 3 "" |
| 12 | .UC 7 |
| 13 | .SH NAME |
| 14 | funopen, fropen, fwopen \- open a stream |
| 15 | .SH SYNOPSIS |
| 16 | .nf |
| 17 | .ft B |
| 18 | #include <stdio.h> |
| 19 | |
| 20 | FILE * |
| 21 | funopen(void *cookie, int (*readfn)(void *, char *, int), |
| 22 | .RS |
| 23 | .\" old man macros need the reset of bold mode |
| 24 | .ft B |
| 25 | int (*writefn)(void *, char *, int), |
| 26 | fpos_t (*seekfn)(void *, off_t, int), int (*closefn)(void *)); |
| 27 | .RE |
| 28 | .\" old man macros need the reset of bold mode |
| 29 | .ft B |
| 30 | |
| 31 | FILE * |
| 32 | fropen(void *cookie, int (*readfn)(void *, char *, int)); |
| 33 | |
| 34 | FILE * |
| 35 | fwopen(void *cookie, int (*writefn)(void *, char *, int)); |
| 36 | .ft R |
| 37 | .fi |
| 38 | .SH DESCRIPTION |
| 39 | .I Funopen |
| 40 | associates a stream with up to four ``I/O functions''. |
| 41 | Either |
| 42 | .I readfn |
| 43 | or |
| 44 | .I writefn |
| 45 | must be specified; |
| 46 | the others can be given as an appropriately-typed NULL pointer. |
| 47 | These I/O functions will be used to read, write, seek and |
| 48 | close the new stream. |
| 49 | .PP |
| 50 | In general, omitting a function means that any attempt to perform the |
| 51 | associated operation on the resulting stream will fail. |
| 52 | If the close function is omitted, closing the stream will flush |
| 53 | any buffered output and then succeed. |
| 54 | .PP |
| 55 | The calling conventions of |
| 56 | .IR readfn , |
| 57 | .IR writefn , |
| 58 | .I seekfn |
| 59 | and |
| 60 | .I closefn |
| 61 | must match those, respectively, of |
| 62 | .IR read (2), |
| 63 | .IR write (2), |
| 64 | .IR seek (2), |
| 65 | and |
| 66 | .IR close (2) |
| 67 | with the single exception that they are passed the |
| 68 | .I cookie |
| 69 | argument specified to |
| 70 | .I funopen |
| 71 | in place of the traditional file descriptor argument. |
| 72 | .PP |
| 73 | Read and write I/O functions are allowed to change the underlying buffer |
| 74 | on fully buffered or line buffered streams by calling |
| 75 | .IR setvbuf . |
| 76 | They are also not required to completely fill or empty the buffer. |
| 77 | They are not, however, allowed to change streams from unbuffered to buffered |
| 78 | or to change the state of the line buffering flag. |
| 79 | They must also be prepared to have read or write calls occur on buffers other |
| 80 | than the one most recently specified. |
| 81 | .PP |
| 82 | All user I/O functions can report an error by returning \-1. |
| 83 | Additionally, all of the functions should set the external variable |
| 84 | .I errno |
| 85 | appropriately if an error occurs. |
| 86 | .PP |
| 87 | An error on |
| 88 | .I closefn |
| 89 | does not keep the stream open. |
| 90 | .PP |
| 91 | As a convenience, the include file ``<stdio.h>'' defines the macros |
| 92 | .I fropen |
| 93 | and |
| 94 | .I fwopen |
| 95 | as calls to |
| 96 | .I funopen |
| 97 | with only a read or write function specified. |
| 98 | .SH "SEE ALSO" |
| 99 | fcntl(2), open(2), fclose(3), fopen(3), fseek(3), setbuf(3) |
| 100 | .SH "RETURN VALUES" |
| 101 | Upon successful completion, |
| 102 | .I funopen |
| 103 | returns a FILE pointer. |
| 104 | Otherwise, NULL is returned and the global variable |
| 105 | .I errno |
| 106 | is set to indicate the error. |
| 107 | .SH ERRORS |
| 108 | .TP 15 |
| 109 | [EINVAL] |
| 110 | .I Funopen |
| 111 | was called without either a read or write function. |
| 112 | .I Funopen |
| 113 | may also fail and set errno for any of the errors |
| 114 | specified for the routine |
| 115 | .IR malloc (3). |
| 116 | .SH BUGS |
| 117 | .I Funopen |
| 118 | may not be portable to systems other than BSD. |