plugins/golang/examples/minimal/minimal.go

   1 /* Example plugin.
   2  * Copyright Red Hat
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met:
   7  *
   8  * * Redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer.
  10  *
  11  * * 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  *
  15  * * Neither the name of Red Hat nor the names of its contributors may be
  16  * used to endorse or promote products derived from this software without
  17  * specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  21  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  22  * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
  23  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  26  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  27  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  28  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  29  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 package main
  34
  35 import (
  36         "C"
  37         "libguestfs.org/nbdkit"
  38         "unsafe"
  39 )
  40
  41 var pluginName = "minimal"
  42
  43 type MinimalPlugin struct {
  44         nbdkit.Plugin
  45 }
  46
  47 type MinimalConnection struct {
  48         nbdkit.Connection
  49 }
  50
  51 var size uint64 = 1024 * 1024
  52
  53 func (p *MinimalPlugin) Open(readonly bool) (nbdkit.ConnectionInterface, error) {
  54         return &MinimalConnection{}, nil
  55 }
  56
  57 func (c *MinimalConnection) GetSize() (uint64, error) {
  58         return size, nil
  59 }
  60
  61 func (c *MinimalConnection) PRead(buf []byte, offset uint64,
  62         flags uint32) error {
  63         for i := 0; i < len(buf); i++ {
  64                 buf[i] = 0
  65         }
  66         return nil
  67 }
  68
  69 //----------------------------------------------------------------------
  70 //
  71 // The boilerplate below this line is required by all golang plugins,
  72 // as well as importing "C" and "unsafe" modules at the top of the
  73 // file.
  74
  75 //export plugin_init
  76 func plugin_init() unsafe.Pointer {
  77         // If your plugin needs to do any initialization, you can
  78         // either put it here or implement a Load() method.
  79         // ...
  80
  81         // Then you must call the following function.
  82         return nbdkit.PluginInitialize(pluginName, &MinimalPlugin{})
  83 }
  84
  85 // This is never(?) called, but must exist.
  86 func main() {}