68 lines
1.4 KiB
C
68 lines
1.4 KiB
C
/*
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* This file is part of the UCB release of Plan 9. It is subject to the license
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* terms in the LICENSE file found in the top-level directory of this
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* distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No
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* part of the UCB release of Plan 9, including this file, may be copied,
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* modified, propagated, or distributed except according to the terms contained
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* in the LICENSE file.
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*/
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#include <u.h>
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#include <lib9.h>
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#include <bio.h>
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int64_t
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Bseek(Biobufhdr *bp, int64_t offset, int base)
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{
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int64_t 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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}
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