1nbdkit-cc-plugin(3)                 NBDKIT                 nbdkit-cc-plugin(3)
2
3
4

NAME

6       nbdkit-cc-plugin - write small nbdkit plugins in inline C (and other
7       languages)
8

SYNOPSIS

10        nbdkit cc /path/to/plugin.c [CC=<CC>] [CFLAGS=<CFLAGS>]
11                                    [EXTRA_CFLAGS=<EXTRA_CFLAGS>]
12        nbdkit cc - <<'EOF'
13        ... C code ...
14        EOF
15

DESCRIPTION

17       This plugin allows you to write small nbdkit(1) plugins in C (and some
18       other languages).  When you use this plugin it compiles your source
19       code to a temporary plugin and then jumps into your compiled plugin.
20       It is somewhat similar to nbdkit-sh-plugin(3), except for C source
21       code.  This can also be used to write plugins which are "C scripts".
22
23       Note this is not the way you normally write nbdkit plugins in C.  To
24       understand how to write plugins in C normally, read nbdkit-plugin(3).
25
26   Simple plugin example
27       Simple plugins from the nbdkit source tree can be compiled and run
28       directly using commands such as:
29
30        $ nbdkit cc plugins/example1/example1.c EXTRA_CFLAGS="-I. -Iinclude"
31
32       You can also read the source from stdin using "-":
33
34        $ nbdkit cc - EXTRA_CFLAGS="-I. -Iinclude" \
35                    < plugins/example1/example1.c
36
37       To replace the compiler flags:
38
39        $ nbdkit cc plugins/example1/example1.c \
40                    CFLAGS="-O3 -mavx2 -fPIC -shared"
41
42   Compiler name and flags
43       The plugin parameters "CC", "CFLAGS" and "EXTRA_CFLAGS" (written in
44       uppercase) can be used to control which C compiler and C compiler flags
45       are used.  If not set, the default compiler and flags from when nbdkit
46       was itself compiled from source are used.  To see what those were you
47       can do:
48
49        $ nbdkit cc --dump-plugin
50        ...
51        CC=gcc
52        CFLAGS=-g -O2 -fPIC -shared
53
54       The "CFLAGS" parameter overrides the built-in flags completely.  The
55       "EXTRA_CFLAGS" parameter adds extra flags to the built-in flags.
56
57   Plugin API version
58       Plugins compiled this way must use the same API version as the cc
59       plugin itself uses.  Currently this is "NBDKIT_API_VERSION=2".
60
61   C plugin as a self-contained script
62       You can create a C plugin which is a self-contained script by adding
63       the following lines at the top and ensuring the C source is executable
64       ("chmod +x plugin.c"):
65
66        #if 0
67        exec nbdkit cc "$0" "$@"
68        #endif
69
70       The script can be run as a command with additional nbdkit flags and
71       plugin parameters, eg:
72
73        ./plugin.c -f -v
74        ./plugin.c -p 10000 --filter=cow
75        ./plugin.c param=1
76
77   Using this plugin with other programming languages
78       This plugin can be used with most ahead-of-time compiled programming
79       languages if they can create shared objects (.so files).  The only
80       requirement is that the compiler ("CC") supports an -o option to write
81       a shared object.  Some examples follow.
82
83       Using this plugin with C++
84
85        nbdkit cc CC=g++ source.cpp
86
87       Using this plugin with OCaml
88
89        nbdkit cc CC=ocamlopt \
90                  CFLAGS="-output-obj -runtime-variant _pic NBDKit.cmx -cclib -lnbdkitocaml" \
91                  source.ml
92
93       See nbdkit-ocaml-plugin(3).
94

PARAMETERS

96       The script name, or "-", must appear as the first parameter.
97
98       CC=CC
99       CFLAGS="CFLAGS"
100       EXTRA_CFLAGS="EXTRA_CFLAGS"
101           Override the compiler and flags.  See "Compiler name and flags"
102           above.
103
104       All other parameters on the command line are passed to the plugin.
105

EXAMPLE

107        $ nbdkit cc - <<'EOF'
108        #include <stdint.h>
109        #include <string.h>
110
111        #define NBDKIT_API_VERSION 2
112        #include <nbdkit-plugin.h>
113
114        char data[10*1024*1024];
115
116        #define THREAD_MODEL NBDKIT_THREAD_MODEL_PARALLEL
117
118        static void *
119        my_open (int readonly)
120        {
121          return NBDKIT_HANDLE_NOT_NEEDED;
122        }
123
124        static int64_t
125        my_get_size (void *handle)
126        {
127          return (int64_t) sizeof (data);
128        }
129
130        static int
131        my_pread (void *handle, void *buf,
132                  uint32_t count, uint64_t offset,
133                  uint32_t flags)
134        {
135          memcpy (buf, data+offset, count);
136          return 0;
137        }
138
139        static int
140        my_pwrite (void *handle, const void *buf,
141                   uint32_t count, uint64_t offset,
142                   uint32_t flags)
143        {
144          memcpy (data+offset, buf, count);
145          return 0;
146        }
147
148        static struct nbdkit_plugin plugin = {
149          .name              = "myplugin",
150          .open              = my_open,
151          .get_size          = my_get_size,
152          .pread             = my_pread,
153          .pwrite            = my_pwrite,
154        };
155
156        NBDKIT_REGISTER_PLUGIN(plugin)
157        EOF
158

FILES

160       $plugindir/nbdkit-cc-plugin.so
161           The plugin.
162
163           Use "nbdkit --dump-config" to find the location of $plugindir.
164

VERSION

166       "nbdkit-cc-plugin" first appeared in nbdkit 1.22.
167

SEE ALSO

169       nbdkit(1), nbdkit-plugin(3), nbdkit-sh-plugin(3).
170

AUTHORS

172       Richard W.M. Jones
173
175       Copyright (C) 2020 Red Hat Inc.
176

LICENSE

178       Redistribution and use in source and binary forms, with or without
179       modification, are permitted provided that the following conditions are
180       met:
181
182       •   Redistributions of source code must retain the above copyright
183           notice, this list of conditions and the following disclaimer.
184
185       •   Redistributions in binary form must reproduce the above copyright
186           notice, this list of conditions and the following disclaimer in the
187           documentation and/or other materials provided with the
188           distribution.
189
190       •   Neither the name of Red Hat nor the names of its contributors may
191           be used to endorse or promote products derived from this software
192           without specific prior written permission.
193
194       THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY
195       EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
196       IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
197       PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE
198       LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
199       CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
200       SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
201       BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
202       WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
203       OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
204       ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
205
206
207
208nbdkit-1.28.2                     2021-11-09               nbdkit-cc-plugin(3)
Impressum