include/nbdkit-plugin.h

   1 /* nbdkit
   2  * Copyright (C) 2013-2018 Red Hat Inc.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met:
   8  *
   9  * * Redistributions of source code must retain the above copyright
  10  * notice, this list of conditions and the following disclaimer.
  11  *
  12  * * Redistributions in binary form must reproduce the above copyright
  13  * notice, this list of conditions and the following disclaimer in the
  14  * documentation and/or other materials provided with the distribution.
  15  *
  16  * * Neither the name of Red Hat nor the names of its contributors may be
  17  * used to endorse or promote products derived from this software without
  18  * specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  22  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  23  * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
  24  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  25  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  26  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  27  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  28  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  29  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  30  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 /* See nbdkit-plugin(3) for documentation and how to write a plugin. */
  35
  36 #ifndef NBDKIT_PLUGIN_H
  37 #define NBDKIT_PLUGIN_H
  38
  39 #include <nbdkit-common.h>
  40
  41 #ifdef __cplusplus
  42 extern "C" {
  43 #endif
  44
  45 /* By default, a plugin gets API version 1; but you may request
  46  * version 2 prior to including this header */
  47 #ifndef NBDKIT_API_VERSION
  48 #define NBDKIT_API_VERSION                            1
  49 #elif (NBDKIT_API_VERSION - 0) < 1 || NBDKIT_API_VERSION > 2
  50 #error Unsupported API version
  51 #endif
  52
  53 struct nbdkit_plugin {
  54   /* Do not set these fields directly; use NBDKIT_REGISTER_PLUGIN.
  55    * They exist so that we can support plugins compiled against
  56    * one version of the header with a runtime compiled against a
  57    * different version with more (or fewer) fields.
  58    */
  59   uint64_t _struct_size;
  60   int _api_version;
  61   int _thread_model;
  62
  63   /* Plugins are responsible for these fields; see the documentation
  64    * for semantics, and which fields are optional. New fields will
  65    * only be added at the end of the struct.
  66    */
  67   const char *name;
  68   const char *longname;
  69   const char *version;
  70   const char *description;
  71
  72   void (*load) (void);
  73   void (*unload) (void);
  74
  75   int (*config) (const char *key, const char *value);
  76   int (*config_complete) (void);
  77   const char *config_help;
  78
  79   void * (*open) (int readonly);
  80   void (*close) (void *handle);
  81
  82   int64_t (*get_size) (void *handle);
  83
  84   int (*can_write) (void *handle);
  85   int (*can_flush) (void *handle);
  86   int (*is_rotational) (void *handle);
  87   int (*can_trim) (void *handle);
  88
  89 #if NBDKIT_API_VERSION == 1
  90   int (*pread) (void *handle, void *buf, uint32_t count, uint64_t offset);
  91   int (*pwrite) (void *handle, const void *buf, uint32_t count, uint64_t offset);
  92   int (*flush) (void *handle);
  93   int (*trim) (void *handle, uint32_t count, uint64_t offset);
  94   int (*zero) (void *handle, uint32_t count, uint64_t offset, int may_trim);
  95 #else
  96   int (*_pread_old) (void *, void *, uint32_t, uint64_t);
  97   int (*_pwrite_old) (void *, const void *, uint32_t, uint64_t);
  98   int (*_flush_old) (void *);
  99   int (*_trim_old) (void *, uint32_t, uint64_t);
 100   int (*_zero_old) (void *, uint32_t, uint64_t, int);
 101 #endif
 102
 103   int errno_is_preserved;
 104
 105   void (*dump_plugin) (void);
 106
 107   int (*can_fua) (void *handle);
 108 #if NBDKIT_API_VERSION == 1
 109   int (*_unused1) (void *, void *, uint32_t, uint64_t);
 110   int (*_unused2) (void *, const void *, uint32_t, uint64_t, uint32_t);
 111   int (*_unused3) (void *, uint32_t);
 112   int (*_unused4) (void *, uint32_t, uint64_t, uint32_t);
 113   int (*_unused5) (void *, uint32_t, uint64_t, uint32_t);
 114 #else
 115   int (*pread) (void *handle, void *buf, uint32_t count, uint64_t offset,
 116                 uint32_t flags);
 117   int (*pwrite) (void *handle, const void *buf, uint32_t count,
 118                  uint64_t offset, uint32_t flags);
 119   int (*flush) (void *handle, uint32_t flags);
 120   int (*trim) (void *handle, uint32_t count, uint64_t offset, uint32_t flags);
 121   int (*zero) (void *handle, uint32_t count, uint64_t offset, uint32_t flags);
 122 #endif
 123   /* int (*set_exportname) (void *handle, const char *exportname); */
 124 };
 125
 126 extern void nbdkit_set_error (int err);
 127
 128 #define NBDKIT_REGISTER_PLUGIN(plugin)                                  \
 129   NBDKIT_CXX_LANG_C                                                     \
 130   struct nbdkit_plugin *                                                \
 131   plugin_init (void)                                                    \
 132   {                                                                     \
 133     (plugin)._struct_size = sizeof (plugin);                            \
 134     (plugin)._api_version = NBDKIT_API_VERSION;                         \
 135     (plugin)._thread_model = THREAD_MODEL;                              \
 136     return &(plugin);                                                   \
 137   }
 138
 139 #ifdef __cplusplus
 140 }
 141 #endif
 142
 143 #endif /* NBDKIT_PLUGIN_H */