#include "sys/param.h" #include "sys/systm.h" #include "sys/inode.h" #include "sys/dir.h" #include "sys/user.h" #include "sys/buf.h" /* * Bmap defines the structure of file system storage * by returning the physical block number on a device given the * inode and the logical block number in a file. * When convenient, it also leaves the physical * block number of the next block of the file in rablock * for use in read-ahead. */ daddr_t bmap(ip, bn, rwflg) register struct inode *ip; daddr_t bn; { register i; struct buf *bp, *nbp; int j, sh; daddr_t nb, *bap; dev_t dev; if ((bn < 0) || (rwflg==B_WRITE && bn >= u.u_limit)) { u.u_error = EFBIG; return((daddr_t)-1); } dev = ip->i_dev; rablock = 0; /* * blocks 0..NADDR-4 are direct blocks */ if(bn < NADDR-3) { i = bn; nb = ip->i_addr[i]; if(nb == 0) { if(rwflg==B_READ || (bp = alloc(dev))==NULL) return((daddr_t)-1); nb = bp->b_blkno; bdwrite(bp); ip->i_addr[i] = nb; ip->i_flag |= IUPD|ICHG; } if(i < NADDR-4) rablock = ip->i_addr[i+1]; return(nb); } /* * addresses NADDR-3, NADDR-2, and NADDR-1 * have single, double, triple indirect blocks. * the first step is to determine * how many levels of indirection. */ sh = 0; nb = 1; bn -= NADDR-3; for(j=3; j>0; j--) { sh += NSHIFT; nb <<= NSHIFT; if(bn < nb) break; bn -= nb; } if(j == 0) { u.u_error = EFBIG; return((daddr_t)-1); } /* * fetch the address from the inode */ nb = ip->i_addr[NADDR-j]; if(nb == 0) { if(rwflg==B_READ || (bp = alloc(dev))==NULL) return((daddr_t)-1); nb = bp->b_blkno; bdwrite(bp); ip->i_addr[NADDR-j] = nb; ip->i_flag |= IUPD|ICHG; } /* * fetch through the indirect blocks */ for(; j<=3; j++) { bp = bread(dev, nb); if(u.u_error) { brelse(bp); return((daddr_t)-1); } bap = bp->b_un.b_daddr; sh -= NSHIFT; i = (bn>>sh) & NMASK; nb = bap[i]; if(nb == 0) { if(rwflg==B_READ || (nbp = alloc(dev))==NULL) { brelse(bp); return((daddr_t)-1); } nb = nbp->b_blkno; bdwrite(nbp); bap[i] = nb; bdwrite(bp); } else brelse(bp); } /* * calculate read-ahead. */ if(i < NINDIR-1) rablock = bap[i+1]; return(nb); } /* * Pass back c to the user at his location u_base; * update u_base, u_count, and u_offset. Return -1 * on the last character of the user's read. * u_base is in the user data space. */ passc(c) register c; { if(subyte(u.u_base, c) < 0) { u.u_error = EFAULT; return(-1); } u.u_count--; u.u_offset++; u.u_base++; return(u.u_count == 0? -1: 0); } /* * Pick up and return the next character from the user's * write call at location u_base; * update u_base, u_count, and u_offset. Return -1 * when u_count is exhausted. * u_base is in the user data space. */ cpass() { register c; if(u.u_count == 0) return(-1); if ((c = fubyte(u.u_base)) < 0) { u.u_error = EFAULT; return(-1); } u.u_count--; u.u_offset++; u.u_base++; return(c); } /* * Routine which sets a user error; placed in * illegal entries in the bdevsw and cdevsw tables. */ nodev() { u.u_error = ENODEV; } /* * Null routine; placed in insignificant entries * in the bdevsw and cdevsw tables. */ nulldev() { }