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Annotation of coherent/d/286_KERNEL/USRSRC/coh/fifo_write.c, revision 1.1.1.1

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

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