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Annotation of coherent/g/usr/lib/misc/fifo_b.c, revision 1.1.1.1

1.1       root        1: /*
                      2:  * fifo_b.c -- Extra routines for handling typed fifos.
                      3:  * Both fifo_b.c (boot fifo) and fifo_k.c (kernel fifo) are needed by the
                      4:  * boot code.
                      5:  */
                      6: #include <kernel/typed.h>
                      7: 
                      8: #ifndef T_NULL
                      9: #define T_NULL ((char *)0)
                     10: #endif
                     11: 
                     12: /* How long is an open fifo?  */
                     13: long
                     14: fifo_len(ffp)
                     15:        FIFO *ffp;
                     16: {
                     17:        /* ffp->f_offset points at the terminating NUL space.  */
                     18:        return(sizeof(typed_space) +
                     19:                ((char *) ffp->f_offset) - ((char *)ffp->f_space));
                     20: } /* fifo_len() */
                     21: 
                     22: /* Write a typed space into a FIFO.  */
                     23: typed_space *
                     24: fifo_write(ffp, space)
                     25:        FIFO *ffp;
                     26:        typed_space *space;
                     27: {
                     28:        return  (fifo_write_untyped(
                     29:                        ffp,
                     30:                        space->ts_data,
                     31:                        (int32) (space->ts_size - sizeof(typed_space)),
                     32:                        space->ts_type)
                     33:                );
                     34: } /* fifo_write() */
                     35: 
                     36: /* Write a chunk of data into an open fifo as a typed space.
                     37:  * Takes a FIFO to be written to, ffp; a pointer to the data, datum; a
                     38:  * size for the datum, size; and a type for the new space, type.
                     39:  *
                     40:  * Returns a pointer to the newly written space.  Returns NULL if the
                     41:  * new space could not be written.
                     42:  *
                     43:  * Note that while sizes throughout this package refer to TOTAL sizes
                     44:  * including headers, the size argument here is ONLY for the datum.
                     45:  *
                     46:  * Only FIFOs of type T_FIFO_SIC are implimented.
                     47:  */
                     48: typed_space *
                     49: fifo_write_untyped(ffp, datum, size, type)
                     50:        FIFO *ffp;
                     51:        char *datum;
                     52:        long size;
                     53:        space_type type;
                     54: {
                     55:        long needed_space;      /* Total space we need to add.  */
                     56:        typed_space *retval;    /* Return the space we just wrote.  */
                     57: 
                     58:        /* Write MUST be set.  */
                     59:        if (F_WRITE != F_WRITE & ffp->f_flags ) {
                     60:                /* Write on closed ffp. */
                     61:                return(T_NULL);  /* This ffp is not open for writing.  */
                     62:        }
                     63: 
                     64:        /* From here to end of fifo_write_untyped() is really fifo_write_sic().  */
                     65: 
                     66:        /* Check to see that there is enough space for the new datum.
                     67:         * We need space for another typed_space header, size bytes of
                     68:         * data, and space for a terminating typed_space header.
                     69:         */
                     70:        needed_space = sizeof(typed_space) + size + sizeof(typed_space);
                     71: 
                     72:        if (ffp->f_space->ts_size <
                     73:            ((char *)ffp->f_offset - (char *)ffp->f_space) + needed_space) {
                     74:                /* Write on insufficient space. */
                     75:                return(T_NULL);         /* Insufficient space.  */
                     76:        }
                     77: 
                     78:        /* ASSERTION:  There is enough space remaining in ffp->f_space for
                     79:         * two more headers and the datum.
                     80:         */
                     81: 
                     82:        retval = ffp->f_offset;
                     83: 
                     84:        /* Create the new header.  */
                     85:        ffp->f_offset->ts_size = sizeof(typed_space) + size;
                     86:        ffp->f_offset->ts_type = type;
                     87: 
                     88:        /* Copy the datum in place.  */
                     89:        memcpy(ffp->f_offset->ts_data, datum, size);
                     90: 
                     91:        /* Advance the write pointer.  */
                     92:        ffp->f_offset += 1;             /* Skip the header.     */
                     93:        (char *) ffp->f_offset += size; /* Skip the data.       */
                     94: 
                     95:        /* Terminate the fifo.  */
                     96:        ffp->f_offset->ts_size = (int32) 0;
                     97:        ffp->f_offset->ts_type = T_UNKNOWN;
                     98: 
                     99:        return(retval);
                    100: } /* fifo_write_untyped() */
                    101: 

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