#include?“devices/block.h“
#include?
#include?
#include?
#include?“devices/ide.h“
#include?“threads/malloc.h“

/*?A?block?device.?*/
struct?block
??{
????struct?list_elem?list_elem;?????????/*?Element?in?all_blocks.?*/

????char?name[16];??????????????????????/*?Block?device?name.?*/
????enum?block_type?type;????????????????/*?Type?of?block?device.?*/
????block_sector_t?size;?????????????????/*?Size?in?sectors.?*/

????const?struct?block_operations?*ops;??/*?Driver?operations.?*/
????void?*aux;??????????????????????????/*?Extra?data?owned?by?driver.?*/

????unsigned?long?long?read_cnt;????????/*?Number?of?sectors?read.?*/
????unsigned?long?long?write_cnt;???????/*?Number?of?sectors?written.?*/
??};

/*?List?of?all?block?devices.?*/
static?struct?list?all_blocks?=?LIST_INITIALIZER?（all_blocks）;

/*?The?block?block?assigned?to?each?Pintos?role.?*/
static?struct?block?*block_by_role[BLOCK_ROLE_CNT];

static?struct?block?*list_elem_to_block?（struct?list_elem?*）;

/*?Returns?a?human-readable?name?for?the?given?block?device
???TYPE.?*/
const?char?*
block_type_name?（enum?block_type?type）
{
??static?const?char?*block_type_names[BLOCK_CNT]?=
????{
??????“kernel“
??????“filesys“
??????“scratch“
??????“swap“
??????“raw“
??????“foreign“
????};

??ASSERT?（type???return?block_type_names[type];
}

/*?Returns?the?block?device?fulfilling?the?given?ROLE?or?a?null
???pointer?if?no?block?device?has?been?assigned?that?role.?*/
struct?block?*
block_get_role?（enum?block_type?role）
{
??ASSERT?（role???return?block_by_role[role];
}

/*?Assigns?BLOCK?the?given?ROLE.?*/
void
block_set_role?（enum?block_type?role?struct?block?*block）
{
??ASSERT?（role???block_by_role[role]?=?block;
}

/*?Returns?the?first?block?device?in?kernel?probe?order?or?a
???null?pointer?if?no?block?devices?are?registered.?*/
struct?block?*
block_first?（void）
{
??return?list_elem_to_block?（list_begin?（&all_blocks））;
}

/*?Returns?the?block?device?following?BLOCK?in?kernel?probe
???order?or?a?null?pointer?if?BLOCK?is?the?last?block?device.?*/
struct?block?*
block_next?（struct?block?*block）
{
??return?list_elem_to_block?（list_next?（&block->list_elem））;
}

/*?Returns?the?block?device?with?the?given?NAME?or?a?null
???pointer?if?no?block?device?has?that?name.?*/
struct?block?*
block_get_by_name?（const?char?*name）
{
??struct?list_elem?*e;

??for?（e?=?list_begin?（&all_blocks）;?e?!=?list_end?（&all_blocks）;
???????e?=?list_next?（e））
????{
??????struct?block?*block?=?list_entry?（e?struct?block?list_elem）;
??????if?（!strcmp?（name?block->name））
????????return?block;
????}

??return?NULL;
}

/*?Verifies?that?SECTOR?is?a?valid?offset?within?BLOCK.
???Panics?if?not.?*/
static?void
check_sector?（struct?block?*block?block_sector_t?sector）
{
??if?（sector?>=?block->size）
????{
??????/*?We?do?not?use?ASSERT?because?we?want?to?panic?here
?????????regardless?of?whether?NDEBUG?is?defined.?*/
??????PANIC?（“Access?past?end?of?device?%s?