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	bseek.c - 9base - revived minimalist port of Plan 9 userland to Unix
	git clone git://git.suckless.org/9base
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	bseek.c (929B)
	---
	1 #include "lib9.h"
	2 #include <bio.h>
	3
	4 long long
	5 Bseek(Biobuf *bp, long long offset, int base)
	6 {
	7 vlong n, d;
	8 int bufsz;
	9
	10 switch(bp->state) {
	11 default:
	12 fprint(2, "Bseek: unknown state %d\n", bp->state);
	13 return Beof;
	14
	15 case Bracteof:
	16 bp->state = Bractive;
	17 bp->icount = 0;
	18 bp->gbuf = bp->ebuf;
	19
	20 case Bractive:
	21 n = offset;
	22 if(base == 1) {
	23 n += Boffset(bp);
	24 base = 0;
	25 }
	26
	27 /*
	28 * try to seek within buffer
	29 */
	30 if(base == 0) {
	31 d = n - Boffset(bp);
	32 bufsz = bp->ebuf - bp->gbuf;
	33 if(-bufsz <= d && d <= bufsz){
	34 bp->icount += d;
	35 if(d >= 0) {
	36 if(bp->icount <= 0)
	37 return n;
	38 } else {
	39 if(bp->ebuf - bp->gbuf >= -bp->i…
	40 return n;
	41 }
	42 }
	43 }
	44
	45 /*
	46 * reset the buffer
	47 */
	48 n = lseek(bp->fid, n, base);
	49 bp->icount = 0;
	50 bp->gbuf = bp->ebuf;
	51 break;
	52
	53 case Bwactive:
	54 Bflush(bp);
	55 n = seek(bp->fid, offset, base);
	56 break;
	57 }
	58 bp->offset = n;
	59 return n;
	60 }