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Annotation of coherent/d/PS2_KERNEL/coh.286/fifo_write.c, revision 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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