Вот такой туториал ;-)
On Thu, 27 Oct 2005 10:36:53 -0500, Steve Dobbelstein wrote:
> John Antypas <[EMAIL PROTECTED]> wrote on 10/26/2005 08:31:17 PM:
>
>> EVMS'ers,
>>
>> I've got some of this, but I'm missing the obvious I'm sure. I'm trying
>> to tie EVMS into higher-level interfaces. For many tasks, the EVMS CLI
>> works fine, but if I want to do someting like scan the object tree,
>> finding hte various childrne of a given object, say a disk, all the way
>> to the end, I need it appers, to use the API.
>>
>> I understand the this involes getting the handles of the object in
>> quetion, but it's the data structures that throw me. Is there anywhere,
>> or anyone, that cna show me a map of what a handle returns, and how I
>> follow it up in the data structure. I'm hoping to map all of this into
>> JAVA objects.
>>
>> Any ideas?
>
> Hi, John.
>
> Here is an introductory description of how it works.
>
> Call evms_get_info() to get information on the entity behind the handle.
> evms_get_info() returns a pointer to a handle_object_info_t, defined in
> include/appstructs.h.
>
> typedef struct handle_object_info_s {
> object_type_t type;
> object_info_t info;
> } __attribute__ ((packed)) handle_object_info_t;
>
> The handle_object_info_t contains a "type" followed by "info" which is an
> object_info_t union. The type says which field of the union is used. The
> types are defined in include/common.h
>
> typedef enum {
> PLUGIN = (1<<0),
> DISK = (1<<1),
> SEGMENT = (1<<2),
> REGION = (1<<3),
> EVMS_OBJECT = (1<<4),
> CONTAINER = (1<<5),
> VOLUME = (1<<6),
> TASK = (1<<7)
> } object_type_t;
>
> For example, a type of SEGMENT says to use the .segment field of the
> union. The .segment field is a storage_object_info_t (defined in
> include/appstructs.h), which contains information on a storage object, in
> this example, information about the segment. The storage object_info_t
> contains information such as the handle of the plug-in that owns the
> object, a handle array of the object's parents, a handle array of the
> object's children, a handle of the container that consumes the object (if
> any), a handle of the container that produces the object (if any), etc.
>
> typedef struct storage_object_info_s {
> object_handle_t handle; /* Handle of this
> object */
> object_type_t object_type; /* SEGMENT, REGION,
> DISK ,... */
> data_type_t data_type; /* DATA_TYPE,
> META_DATA_TYPE, FREE_SPACE_TYPE */
> u_int32_t dev_major; /* Device major number */
> u_int32_t dev_minor; /* Device minor number */
> object_handle_t disk_group; /* Disk group in which
> this
> object resides */
> plugin_handle_t plugin; /* Handle of the
> plug-in that manages */
> /* this storage object */
> object_handle_t producing_container; /* storage_container
> that produced this object */
> object_handle_t consuming_container; /* storage_container
> that consumed this object */
> handle_array_t * parent_objects; /* List of parent
> objects, filled in by parent */
> handle_array_t * child_objects; /* List of objects
> that this object comprises */
> u_int32_t flags; /* Defined by
> SOFLAG_???? defines */
> char name[EVMS_NAME_SIZE+1]; /* Object's name */
> lba_t start; /* Relative starting
> block of this object */
> sector_count_t size; /* Size of the storage
> object in sectors */
> geometry_t geometry; /* Optional object
> geometry
> */
> object_handle_t volume; /* Volume to which
> this object belongs */
> } __attribute__ ((packed)) storage_object_info_t;
>
> Here is a sample function for displaying the name of the entity
> represented by a handle.
>
> int display_name(engine_handle_t handle) {
>
> int rc;
> handle_object_info_t *info = NULL;
>
> rc = evms_get_info(handle, &info);
> if (rc != 0) {
> printf("Could not get info about handle %d. Error code is %d:
> %s\n",
> handle, rc, evms_strerror(rc));
> return rc;
> }
> }
> switch (info->type) {
> case DISK:
> printf("Handle %d is for disk %s.\n",
> handle, info->info.disk.name);
> break;
> case SEGMENT:
> printf("Handle %d is for segment %s.\n",
> handle, info->info.segment.name);
> break;
> case REGION:
> printf("Handle %d is for region %s.\n",
> handle, info->info.region.name);
> break;
> case EVMS_OBJECT:
> printf("Handle %d is for EVMS object %s.\n",
> handle, info->info.object.name);
> break;
> case CONTAINER:
> printf("Handle %d is for container %s.\n",
> handle, info->info.container.name);
> break;
> case VOLUME:
> printf("Handle %d is for volume %s.\n",
> handle, info->info.volume.name);
> break;
> case PLUGIN:
> printf("Handle %d is for plug-in %s.\n",
> handle, info->info.plugin.long_name);
> break;
> default:
> printf("Handle %d is for a thing of unknown type %x.\n",
> handle, info->type);
> break;
> }
> }
> evms_free(info);
>
> return rc;
> }
> }
> Once you get the info for a handle you can then call evms_get_info() for
> any of the handles contained in the info. (The following code is for
> illustration. I typed it into the email. I'm not sure if it will
> actually compile.)
>
> engine_handle_t segment_handle;
> handle_object_info_t *segment_info = NULL; handle_object_info_t
> *consuming_container_info = NULL; handle_object_info_t *parent_info =
> NULL; int i;
>
> rc = evms_get_info(segment_handle, &segment_info); if (rc == 0) {
> if (segment_info->info.segment.consuming_container != 0) {
> rc =
> evms_get_info(segment_info->info.segment.consuming_container,
> &consuming_container_info);
>
> printf("Segment %s is consumed by container %s.\n",
> segment_info->info.segment.name,
> consuming_container_info->info.container.name);
> }
> }
> printf("Segment %s has %d parent(s)\n",
> segment_info->info.segment.name,
> segment_info->info.segment.parent_objects->count);
> for (i=0; i < segment_info->info.segment.parent_objects->count; i++)
> {
> rc =
> evms_get_info(segment_info->info.segment.parent_objects->handle[i],
> &parent_info);
> printf("Parent object %d is %s\n",
> i,
> parent_info->info.segment.name);
> }
> }
> }
> See ui/utils/evms_query.c for an example of how to walk the object tree
> structure using engine handles and the info structures.
>
> That's a start. Hope it helps. Post if you have any further questions.
>
> Steve D.
>
>
>
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