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#include	<u.h>
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#include	<libc.h>
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#include	<bio.h>
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vlong
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Bseek(Biobufhdr *bp, vlong offset, int base)
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{
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	vlong n, d;
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	switch(bp->state) {
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	default:
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		fprint(2, "Bseek: unknown state %d\n", bp->state);
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		return Beof;
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	case Bracteof:
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		bp->state = Bractive;
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		bp->icount = 0;
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		bp->gbuf = bp->ebuf;
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	case Bractive:
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		n = offset;
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		if(base == 1) {
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			n += Boffset(bp);
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			base = 0;
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		}
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		/*
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		 * try to seek within buffer
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		 */
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		if(base == 0) {
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			/*
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			 * if d is too large for an int, icount may wrap,
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			 * so we need to ensure that icount hasn't wrapped
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			 * and points within the buffer's valid data.
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			 */
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			d = n - Boffset(bp);
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			bp->icount += d;
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			if(d <= bp->bsize && bp->icount <= 0 &&
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			    bp->ebuf - bp->gbuf >= -bp->icount)
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				return n;
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		}
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		/*
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		 * reset the buffer
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		 */
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		n = seek(bp->fid, n, base);
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		bp->icount = 0;
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		bp->gbuf = bp->ebuf;
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		break;
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	case Bwactive:
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		Bflush(bp);
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		n = seek(bp->fid, offset, base);
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		break;
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	}
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	bp->offset = n;
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	return n;
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}