104 lines
2.4 KiB
C
104 lines
2.4 KiB
C
#include "fs.h"
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#include "buf.h"
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#include "inode.h"
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#include <sys/types.h>
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#include <stdlib.h>
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#include <string.h>
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static struct buf *new_block(dev_t dev, pino_t inum);
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/*===========================================================================*
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* buf_pool *
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*===========================================================================*/
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void buf_pool(void)
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{
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/* Initialize the buffer pool. */
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front = NULL;
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rear = NULL;
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}
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/*===========================================================================*
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* get_block *
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*===========================================================================*/
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struct buf *get_block(dev_t dev, pino_t inum)
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{
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struct buf *bp = front;
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while(bp != NULL) {
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if (bp->b_dev == dev && bp->b_num == inum) {
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bp->b_count++;
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return(bp);
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}
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bp = bp->b_next;
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}
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/* Buffer was not found. Try to allocate a new one */
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return new_block(dev, inum);
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}
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/*===========================================================================*
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* new_block *
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*===========================================================================*/
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static struct buf *new_block(dev_t dev, pino_t inum)
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{
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/* Allocate a new buffer and add it to the double linked buffer list */
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struct buf *bp;
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bp = malloc(sizeof(struct buf));
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if (bp == NULL) {
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err_code = ENOSPC;
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return(NULL);
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}
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bp->b_num = inum;
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bp->b_dev = dev;
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bp->b_bytes = 0;
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bp->b_count = 1;
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memset(bp->b_data, 0 , PIPE_BUF);
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/* Add at the end of the buffer */
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if (front == NULL) { /* Empty list? */
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front = bp;
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bp->b_prev = NULL;
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} else {
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rear->b_next = bp;
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bp->b_prev = rear;
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}
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bp->b_next = NULL;
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rear = bp;
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return(bp);
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}
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/*===========================================================================*
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* put_block *
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*===========================================================================*/
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void put_block(dev_t dev, pino_t inum)
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{
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struct buf *bp;
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bp = get_block(dev, inum);
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if (bp == NULL) return; /* We didn't find the block. Nothing to put. */
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bp->b_count--; /* Compensate for above 'get_block'. */
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if (--bp->b_count > 0) return;
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/* Cut bp out of the loop */
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if (bp->b_prev == NULL)
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front = bp->b_next;
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else
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bp->b_prev->b_next = bp->b_next;
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if (bp->b_next == NULL)
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rear = bp->b_prev;
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else
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bp->b_next->b_prev = bp->b_prev;
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/* Buffer administration is done. Now it's safe to free up bp. */
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free(bp);
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}
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