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Annotation of 42BSD/ingres/source/libq/IIpb_get.c, revision 1.1.1.1

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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