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#include <kernel/con.h>
#include <kernel/fs.h>
#include <stdint.h>
#include <string.h>
/* memory dedicated to the block cache */
#define BSTART 0x80000
#define BEND 0xA0000
static struct buffer *lru;
static struct buffer *mru;
struct buffer *buffer_get_block(uint16_t device, uint16_t block);
void buffer_init(void) {
int c = 0;
struct buffer *last = NULL;
struct buffer *b = (struct buffer*) BSTART;
void *d = (void*) (BEND - BLOCK_SIZE);
while(d > (void*) b) {
memset(b, 0, sizeof(struct buffer));
b->b_data = d;
b->b_prev = last;
if(last)
last->b_next = b;
last = b;
b = (struct buffer*) ((void*) b + sizeof(struct buffer));
d = (void*) (d - (void*) BLOCK_SIZE);
c++;
}
lru = (struct buffer*) BSTART;
mru = last;
printk("[buf] Buffers initialized (0x%x buffers in pool)\n", c);
}
struct buffer *buffer_get_block(uint16_t device, uint16_t block) {
int ret;
struct buffer **p = &mru;
struct buffer *b;
/* check if the requested block is already in the cache */
while(*p) {
if((*p)->b_device == device && (*p)->b_block == block) {
/* put the buffer back at the MRU end of the list */
(*p)->b_next = NULL;
(*p)->b_prev = mru;
mru = *p;
return *p;
}
p = &(*p)->b_prev;
}
/* find a buffer at the end of the LRU list */
b = lru;
lru = lru->b_next;
lru->b_prev = NULL;
ret = block_read(b->b_data, block);
/* abort if we failed to read in the block */
if(ret < 0) {
/* release the allocated buffer to the pool */
lru->b_prev = b;
b->b_next = lru;
b->b_prev = NULL;
lru = b;
return NULL;
}
b->b_device = device;
b->b_block = block;
/* put the buffer back at the MRU end of the list */
b->b_next = NULL;
b->b_prev = mru;
mru = b;
return b;
}
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