fiss

Friedel's Initialization and Service Supervision
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bseek.c (1035B)

      1 #include "common.h"
      2 #include "lib9.h"
      3 
      4 #include <bio.h>
      5 
      6 long long
      7 Bseek(Biobuf* bp, long long offset, int base) {
      8 	vlong n, d;
      9 	int   bufsz;
     10 
     11 	switch (bp->state) {
     12 		default:
     13 			fprint(2, "Bseek: unknown state %d\n", bp->state);
     14 			return Beof;
     15 
     16 		case Bracteof:
     17 			bp->state  = Bractive;
     18 			bp->icount = 0;
     19 			bp->gbuf   = bp->ebuf;
     20 
     21 			FALLTHROUGH;
     22 		case Bractive:
     23 			n = offset;
     24 			if (base == 1) {
     25 				n += Boffset(bp);
     26 				base = 0;
     27 			}
     28 
     29 			/*
     30 			 * try to seek within buffer
     31 			 */
     32 			if (base == 0) {
     33 				d     = n - Boffset(bp);
     34 				bufsz = bp->ebuf - bp->gbuf;
     35 				if (-bufsz <= d && d <= bufsz) {
     36 					bp->icount += d;
     37 					if (d >= 0) {
     38 						if (bp->icount <= 0)
     39 							return n;
     40 					} else {
     41 						if (bp->ebuf - bp->gbuf >= -bp->icount)
     42 							return n;
     43 					}
     44 				}
     45 			}
     46 
     47 			/*
     48 			 * reset the buffer
     49 			 */
     50 			n          = lseek(bp->fid, n, base);
     51 			bp->icount = 0;
     52 			bp->gbuf   = bp->ebuf;
     53 			break;
     54 
     55 		case Bwactive:
     56 			Bflush(bp);
     57 			n = seek(bp->fid, offset, base);
     58 			break;
     59 	}
     60 	bp->offset = n;
     61 	return n;
     62 }