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.\" ========================================================================
.\"
.IX Title "nbdkit-cc-plugin 3"
.TH nbdkit-cc-plugin 3 2024-04-21 nbdkit-1.38.1 NBDKIT
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH NAME
nbdkit\-cc\-plugin \- write small nbdkit plugins in inline C
(and other languages)
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 2
\& nbdkit cc /path/to/plugin.c [CC=<CC>] [CFLAGS=<CFLAGS>]
\&                             [EXTRA_CFLAGS=<EXTRA_CFLAGS>]
.Ve
.PP
.Vb 3
\& nbdkit cc \- <<\*(AqEOF\*(Aq
\& ... C code ...
\& EOF
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
This plugin allows you to write small \fBnbdkit\fR\|(1) plugins in C (and
some other languages).  When you use this plugin it compiles your
source code to a temporary plugin and then jumps into your compiled
plugin.  It is somewhat similar to \fBnbdkit\-sh\-plugin\fR\|(3), except for
C source code.  This can also be used to write plugins which are "C
scripts".
.PP
\&\fBNote\fR this is not the way you normally write nbdkit plugins in C.
To understand how to write plugins in C normally, read
\&\fBnbdkit\-plugin\fR\|(3).
.SS "Simple plugin example"
.IX Subsection "Simple plugin example"
Simple plugins from the nbdkit source tree can be compiled and run
directly using commands such as:
.PP
.Vb 1
\& $ nbdkit cc plugins/example1/example1.c EXTRA_CFLAGS="\-I. \-Iinclude"
.Ve
.PP
You can also read the source from stdin using \f(CW\*(C`\-\*(C'\fR:
.PP
.Vb 2
\& $ nbdkit cc \- EXTRA_CFLAGS="\-I. \-Iinclude" \e
\&             < plugins/example1/example1.c
.Ve
.PP
To replace the compiler flags:
.PP
.Vb 2
\& $ nbdkit cc plugins/example1/example1.c \e
\&             CFLAGS="\-O3 \-mavx2 \-fPIC \-shared"
.Ve
.SS "Compiler name and flags"
.IX Subsection "Compiler name and flags"
The plugin parameters \f(CW\*(C`CC\*(C'\fR, \f(CW\*(C`CFLAGS\*(C'\fR and \f(CW\*(C`EXTRA_CFLAGS\*(C'\fR (written in
uppercase) can be used to control which C compiler and C compiler
flags are used.  If not set, the default compiler and flags from when
nbdkit was itself compiled from source are used.  To see what those
were you can do:
.PP
.Vb 4
\& $ nbdkit cc \-\-dump\-plugin
\& ...
\& CC=gcc
\& CFLAGS=\-g \-O2 \-fPIC \-shared
.Ve
.PP
The \f(CW\*(C`CFLAGS\*(C'\fR parameter overrides the built-in flags completely.  The
\&\f(CW\*(C`EXTRA_CFLAGS\*(C'\fR parameter adds extra flags to the built-in flags.
.SS "Plugin API version"
.IX Subsection "Plugin API version"
Plugins compiled this way must use the same API version as the cc
plugin itself uses.  Currently this is \f(CW\*(C`NBDKIT_API_VERSION=2\*(C'\fR.
.SS "C plugin as a self-contained script"
.IX Subsection "C plugin as a self-contained script"
You can create a C plugin which is a self-contained script by adding
the following lines at the top and ensuring the C source is executable
(\f(CW\*(C`chmod\ +x\ plugin.c\*(C'\fR):
.PP
.Vb 3
\& #if 0
\& exec nbdkit cc "$0" "$@"
\& #endif
.Ve
.PP
The script can be run as a command with additional nbdkit flags and
plugin parameters, eg:
.PP
.Vb 3
\& ./plugin.c \-f \-v
\& ./plugin.c \-p 10000 \-\-filter=cow
\& ./plugin.c param=1
.Ve
.SS "Using this plugin with C++"
.IX Subsection "Using this plugin with C++"
.Vb 1
\& nbdkit cc CC=g++ source.cpp
.Ve
.PP
C++ plugin scripts can be created similarly to C, but you must add
\&\f(CW\*(C`CC=g++\*(C'\fR as a parameter to exec nbdkit.
.SS "Using this plugin with OCaml"
.IX Subsection "Using this plugin with OCaml"
.Vb 3
\& nbdkit cc CC=ocamlopt \e
\&           CFLAGS="\-output\-obj \-runtime\-variant _pic  NBDKit.cmx \-cclib \-lnbdkitocaml" \e
\&           source.ml
.Ve
.PP
OCaml plugin scripts can be created using this trick:
.PP
.Vb 7
\& (*/.)>/dev/null 2>&1
\& exec nbdkit cc "$0" \e
\&      CC=ocamlopt \e
\&      CFLAGS="\-output\-obj \-runtime\-variant _pic  NBDKit.cmx \-cclib \-lnbdkitocaml" \e
\&      "$@"
\& *)
\& (* followed by OCaml code for the plugin here *)
.Ve
.PP
As with C plugin scripts, the file must be executable.  See also
\&\fBnbdkit\-ocaml\-plugin\fR\|(3).
.SS "Using this plugin with other programming languages"
.IX Subsection "Using this plugin with other programming languages"
This plugin can be used with most ahead-of-time compiled programming
languages if they can create shared objects (\fI.so\fR files).  The only
requirement is that the compiler (\f(CW\*(C`CC\*(C'\fR) supports an \fI\-o\fR option to
write a shared object.
.SH PARAMETERS
.IX Header "PARAMETERS"
The script name, or \f(CW\*(C`\-\*(C'\fR, must appear as the first parameter.
.IP \fBCC=\fRCC 4
.IX Item "CC=CC"
.PD 0
.IP "\fBCFLAGS=""\fRCFLAGS\fB""\fR" 4
.IX Item "CFLAGS=""CFLAGS"""
.IP "\fBEXTRA_CFLAGS=""\fREXTRA_CFLAGS\fB""\fR" 4
.IX Item "EXTRA_CFLAGS=""EXTRA_CFLAGS"""
.PD
Override the compiler and flags.  See "Compiler name and flags"
above.
.PP
All other parameters on the command line are passed to the plugin.
.SH EXAMPLE
.IX Header "EXAMPLE"
.Vb 3
\& $ nbdkit cc \- <<\*(AqEOF\*(Aq
\& #include <stdint.h>
\& #include <string.h>
\&
\& #define NBDKIT_API_VERSION 2
\& #include <nbdkit\-plugin.h>
\&
\& char data[10*1024*1024];
\&
\& #define THREAD_MODEL NBDKIT_THREAD_MODEL_PARALLEL
\&
\& static void *
\& my_open (int readonly)
\& {
\&   return NBDKIT_HANDLE_NOT_NEEDED;
\& }
\&
\& static int64_t
\& my_get_size (void *handle)
\& {
\&   return (int64_t) sizeof (data);
\& }
\&
\& static int
\& my_pread (void *handle, void *buf,
\&           uint32_t count, uint64_t offset,
\&           uint32_t flags)
\& {
\&   memcpy (buf, data+offset, count);
\&   return 0;
\& }
\&
\& static int
\& my_pwrite (void *handle, const void *buf,
\&            uint32_t count, uint64_t offset,
\&            uint32_t flags)
\& {
\&   memcpy (data+offset, buf, count);
\&   return 0;
\& }
\&
\& static struct nbdkit_plugin plugin = {
\&   .name              = "myplugin",
\&   .open              = my_open,
\&   .get_size          = my_get_size,
\&   .pread             = my_pread,
\&   .pwrite            = my_pwrite,
\& };
\&
\& NBDKIT_REGISTER_PLUGIN(plugin)
\& EOF
.Ve
.SH FILES
.IX Header "FILES"
.ie n .IP \fR\fI$plugindir\fR\fI/nbdkit\-cc\-plugin.so\fR 4
.el .IP \fR\f(CI$plugindir\fR\fI/nbdkit\-cc\-plugin.so\fR 4
.IX Item "$plugindir/nbdkit-cc-plugin.so"
The plugin.
.Sp
Use \f(CW\*(C`nbdkit \-\-dump\-config\*(C'\fR to find the location of \f(CW$plugindir\fR.
.SH VERSION
.IX Header "VERSION"
\&\f(CW\*(C`nbdkit\-cc\-plugin\*(C'\fR first appeared in nbdkit 1.22.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBnbdkit\fR\|(1),
\&\fBnbdkit\-plugin\fR\|(3),
\&\fBnbdkit\-eval\-plugin\fR\|(3).
\&\fBnbdkit\-ocaml\-plugin\fR\|(3).
\&\fBnbdkit\-sh\-plugin\fR\|(3).
.SH AUTHORS
.IX Header "AUTHORS"
Richard W.M. Jones
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright Red Hat
.SH LICENSE
.IX Header "LICENSE"
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
.IP \(bu 4
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
.IP \(bu 4
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
.IP \(bu 4
Neither the name of Red Hat nor the names of its contributors may be
used to endorse or promote products derived from this software without
specific prior written permission.
.PP
THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.