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Annotation of researchv10no/sys/os/rdwri.c, revision 1.1

1.1     ! root        1: #include "sys/param.h"
        !             2: #include "sys/inode.h"
        !             3: #include "sys/user.h"
        !             4: #include "sys/conf.h"
        !             5: #include "sys/buf.h"
        !             6: 
        !             7: /*
        !             8:  * Read the file corresponding to
        !             9:  * the inode pointed at by the argument.
        !            10:  * The actual read arguments are found
        !            11:  * in the variables:
        !            12:  *     u_base          core address for destination
        !            13:  *     u_offset        byte offset in file
        !            14:  *     u_count         number of bytes to read
        !            15:  *     u_segflg        read to kernel/user
        !            16:  */
        !            17: readi(ip)
        !            18: register struct inode *ip;
        !            19: {
        !            20: 
        !            21:        if(u.u_count == 0)
        !            22:                return;
        !            23:        ip->i_flag |= IACC;
        !            24:        if (ip->i_sptr) {
        !            25:                u.u_nbadio = 0; /* approximates a bad-count per stream */
        !            26:                stread(ip);
        !            27:                return;
        !            28:        }
        !            29:        (*fstypsw[ip->i_fstyp]->t_read)(ip);
        !            30: }
        !            31: 
        !            32: /*
        !            33:  * Write the file corresponding to
        !            34:  * the inode pointed at by the argument.
        !            35:  * The actual write arguments are found
        !            36:  * in the variables:
        !            37:  *     u_base          core address for source
        !            38:  *     u_offset        byte offset in file
        !            39:  *     u_count         number of bytes to write
        !            40:  *     u_segflg        write to kernel/user/user I
        !            41:  */
        !            42: 
        !            43: writei(ip)
        !            44: register struct inode *ip;
        !            45: {
        !            46: 
        !            47:        if (ip->i_sptr) {
        !            48:                ip->i_flag |= IUPD|ICHG;
        !            49:                stwrite(ip);
        !            50:                return;
        !            51:        }
        !            52:        (*fstypsw[ip->i_fstyp]->t_write)(ip);
        !            53: }
        !            54: 
        !            55: /*
        !            56:  * Return the logical maximum
        !            57:  * of the 2 arguments.
        !            58:  */
        !            59: unsigned
        !            60: max(a, b)
        !            61: unsigned a, b;
        !            62: {
        !            63: 
        !            64:        if(a > b)
        !            65:                return(a);
        !            66:        return(b);
        !            67: }
        !            68: 
        !            69: /*
        !            70:  * Return the logical minimum
        !            71:  * of the 2 arguments.
        !            72:  */
        !            73: unsigned
        !            74: min(a, b)
        !            75: unsigned a, b;
        !            76: {
        !            77: 
        !            78:        if(a < b)
        !            79:                return(a);
        !            80:        return(b);
        !            81: }
        !            82: 
        !            83: /*
        !            84:  * Move n bytes at byte location
        !            85:  * &bp->b_un.b_addr[o] to/from (flag) the
        !            86:  * user/kernel (u.segflg) area starting at u.base.
        !            87:  * Update all the arguments by the number
        !            88:  * of bytes moved.
        !            89:  *
        !            90:  * Botchy VAX-ism: believes user I and user D are the same
        !            91:  */
        !            92: iomove(cp, n, flag)
        !            93:        register caddr_t cp;
        !            94:        register unsigned n;
        !            95: {
        !            96:        register int t;
        !            97: 
        !            98:        if (n==0)
        !            99:                return;
        !           100:        if (u.u_segflg != SEGSYS) {
        !           101:                if (flag==B_WRITE)
        !           102:                        t = copyin(u.u_base, (caddr_t)cp, n);
        !           103:                else
        !           104:                        t = copyout((caddr_t)cp, u.u_base, n);
        !           105:                if (t) {
        !           106:                        u.u_error = EFAULT;
        !           107:                        return;
        !           108:                }
        !           109:        } else
        !           110:                if (flag == B_WRITE)
        !           111:                        bcopy(u.u_base, (caddr_t)cp, n);
        !           112:                else
        !           113:                        bcopy((caddr_t)cp, u.u_base, n);
        !           114:        u.u_base += n;
        !           115:        u.u_offset = Lladd(u.u_offset, n);
        !           116:        u.u_count -= n;
        !           117: }

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