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Annotation of 42BSD/ingres/source/libq/IIpb_get.c, revision 1.1

1.1     ! root        1: # include      <useful.h>
        !             2: # include      <pipes.h>
        !             3: # include      <sccs.h>
        !             4: 
        !             5: SCCSID(@(#)IIpb_get.c  7.1     2/5/81)
        !             6: 
        !             7: 
        !             8: /*
        !             9: **  IIPB_GET -- buffered get from pipe
        !            10: **
        !            11: **     This routine just gets a record from the pipe block, reading
        !            12: **     if necessary.  It tries to do things in big chunks to keep
        !            13: **     the overhead down.
        !            14: **
        !            15: **     Parameters:
        !            16: **             ppb -- a pointer to the pipe block to unbuffer.
        !            17: **             dp -- a pointer to the data area.
        !            18: **             len -- the number of bytes to read.
        !            19: **
        !            20: **     Returns:
        !            21: **             The number of bytes actually read.
        !            22: **             Zero on end of file.
        !            23: **
        !            24: **     Side Effects:
        !            25: **             none.
        !            26: **
        !            27: **     Trace Flags:
        !            28: **             18.1 - 18.7
        !            29: */
        !            30: 
        !            31: IIpb_get(ppb, dp, len)
        !            32: register pb_t  *ppb;
        !            33: char           *dp;
        !            34: register int   len;
        !            35: {
        !            36:        int             rct;
        !            37:        register int    i;
        !            38: 
        !            39:        rct = 0;
        !            40: 
        !            41:        /*
        !            42:        **  Top Loop.
        !            43:        **      As long as we still want more, keep buffering out.
        !            44:        */
        !            45: 
        !            46:        while (len > 0)
        !            47:        {
        !            48:                /* if we have no data, read another block */
        !            49:                while (ppb->pb_nleft <= 0)
        !            50:                {
        !            51:                        if (bitset(PB_EOF, ppb->pb_stat))
        !            52:                                return (rct);
        !            53:                        IIpb_read(ppb);
        !            54:                }
        !            55: 
        !            56:                /*
        !            57:                **  Compute the length to move.
        !            58:                **      This is the min of the amount we want and the
        !            59:                **      amount we have available to us in the buffer.
        !            60:                */
        !            61: 
        !            62:                i = min(ppb->pb_nleft, len);
        !            63:                IIbmove(ppb->pb_xptr, dp, i);
        !            64:                ppb->pb_xptr += i;
        !            65:                ppb->pb_nleft -= i;
        !            66:                dp += i;
        !            67:                len -= i;
        !            68:                rct += i;
        !            69:        }
        !            70: 
        !            71:        return (rct);
        !            72: }

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