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2 - 1 
#include	<u.h>
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#include	<libc.h>
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#include	<bio.h>
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int
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Bgetc(Biobufhdr *bp)
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{
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	int i;
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loop:
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	i = bp->icount;
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	if(i != 0) {
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		bp->icount = i+1;
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		return bp->ebuf[i];
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	}
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	if(bp->state != Bractive) {
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		if(bp->state == Bracteof)
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			bp->state = Bractive;
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		return Beof;
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	}
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	/*
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	 * get next buffer, try to keep Bungetsize
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	 * characters pre-catenated from the previous
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	 * buffer to allow that many ungets.
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	 */
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	memmove(bp->bbuf-Bungetsize, bp->ebuf-Bungetsize, Bungetsize);
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	i = read(bp->fid, bp->bbuf, bp->bsize);
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	bp->gbuf = bp->bbuf;
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	if(i <= 0) {
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		bp->state = Bracteof;
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		if(i < 0)
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			bp->state = Binactive;
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		return Beof;
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	}
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	if(i < bp->bsize) {
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		memmove(bp->ebuf-i-Bungetsize, bp->bbuf-Bungetsize, i+Bungetsize);
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		bp->gbuf = bp->ebuf-i;
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	}
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	bp->icount = -i;
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	bp->offset += i;
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	goto loop;
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}
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int
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Bungetc(Biobufhdr *bp)
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{
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	if(bp->state == Bracteof)
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		bp->state = Bractive;
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	if(bp->state != Bractive)
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		return Beof;
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	bp->icount--;
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	return 1;
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}