include/nbdkit-plugin.h

   1 /* nbdkit
   2  * Copyright (C) 2013-2019 Red Hat Inc.
   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 /* See nbdkit-plugin(3) for documentation and how to write a plugin. */
  34
  35 #ifndef NBDKIT_PLUGIN_H
  36 #define NBDKIT_PLUGIN_H
  37
  38 #include <nbdkit-common.h>
  39
  40 #ifdef __cplusplus
  41 extern "C" {
  42 #endif
  43
  44 /* By default, a plugin gets API version 1; but you may request
  45  * version 2 prior to including this header */
  46 #ifndef NBDKIT_API_VERSION
  47 #define NBDKIT_API_VERSION                            1
  48 #elif (NBDKIT_API_VERSION - 0) < 1 || NBDKIT_API_VERSION > 2
  49 #error Unsupported API version
  50 #endif
  51
  52 struct nbdkit_plugin {
  53   /* Do not set these fields directly; use NBDKIT_REGISTER_PLUGIN.
  54    * They exist so that we can support plugins compiled against
  55    * one version of the header with a runtime compiled against a
  56    * different version with more (or fewer) fields.
  57    */
  58   uint64_t _struct_size;
  59   int _api_version;
  60   int _thread_model;
  61
  62   /* Plugins are responsible for these fields; see the documentation
  63    * for semantics, and which fields are optional. New fields will
  64    * only be added at the end of the struct.
  65    */
  66   const char *name;
  67   const char *longname;
  68   const char *version;
  69   const char *description;
  70
  71   void (*load) (void);
  72   void (*unload) (void);
  73
  74   int (*config) (const char *key, const char *value);
  75   int (*config_complete) (void);
  76   const char *config_help;
  77
  78   void * (*open) (int readonly);
  79   void (*close) (void *handle);
  80
  81   int64_t (*get_size) (void *handle);
  82
  83   int (*can_write) (void *handle);
  84   int (*can_flush) (void *handle);
  85   int (*is_rotational) (void *handle);
  86   int (*can_trim) (void *handle);
  87
  88 #if NBDKIT_API_VERSION == 1
  89   int (*pread) (void *handle, void *buf, uint32_t count, uint64_t offset);
  90   int (*pwrite) (void *handle, const void *buf, uint32_t count, uint64_t offset);
  91   int (*flush) (void *handle);
  92   int (*trim) (void *handle, uint32_t count, uint64_t offset);
  93   int (*zero) (void *handle, uint32_t count, uint64_t offset, int may_trim);
  94 #else
  95   int (*_pread_old) (void *, void *, uint32_t, uint64_t);
  96   int (*_pwrite_old) (void *, const void *, uint32_t, uint64_t);
  97   int (*_flush_old) (void *);
  98   int (*_trim_old) (void *, uint32_t, uint64_t);
  99   int (*_zero_old) (void *, uint32_t, uint64_t, int);
 100 #endif
 101
 102   int errno_is_preserved;
 103
 104   void (*dump_plugin) (void);
 105
 106   int (*can_zero) (void *handle);
 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
 124   const char *magic_config_key;
 125
 126   int (*can_multi_conn) (void *handle);
 127
 128   int (*can_extents) (void *handle);
 129   int (*extents) (void *handle, uint32_t count, uint64_t offset, uint32_t flags,
 130                   struct nbdkit_extents *extents);
 131   int (*can_cache) (void *handle);
 132   int (*cache) (void *handle, uint32_t count, uint64_t offset, uint32_t flags);
 133
 134   int (*thread_model) (void);
 135
 136   int (*can_fast_zero) (void *handle);
 137 };
 138
 139 extern void nbdkit_set_error (int err);
 140
 141 #define NBDKIT_REGISTER_PLUGIN(plugin)                                  \
 142   NBDKIT_CXX_LANG_C                                                     \
 143   struct nbdkit_plugin *                                                \
 144   plugin_init (void)                                                    \
 145   {                                                                     \
 146     (plugin)._struct_size = sizeof (plugin);                            \
 147     (plugin)._api_version = NBDKIT_API_VERSION;                         \
 148     (plugin)._thread_model = THREAD_MODEL;                              \
 149     return &(plugin);                                                   \
 150   }
 151
 152 #ifdef __cplusplus
 153 }
 154 #endif
 155
 156 #endif /* NBDKIT_PLUGIN_H */