1 #include <u.h> 2 #include <libc.h> 3 #include <bio.h> 4 5 vlong 6 Bseek(Biobufhdr *bp, vlong offset, int base) 7 { 8 vlong n, d; 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 /* 32 * if d is too large for an int, icount may wrap, 33 * so we need to ensure that icount hasn't wrapped 34 * and points within the buffer's valid data. 35 */ 36 d = n - Boffset(bp); 37 bp->icount += d; 38 if(d <= bp->bsize && bp->icount <= 0 && 39 bp->ebuf - bp->gbuf >= -bp->icount) 40 return n; 41 } 42 43 /* 44 * reset the buffer 45 */ 46 n = seek(bp->fid, n, base); 47 bp->icount = 0; 48 bp->gbuf = bp->ebuf; 49 break; 50 51 case Bwactive: 52 Bflush(bp); 53 n = seek(bp->fid, offset, base); 54 break; 55 } 56 bp->offset = n; 57 return n; 58 } 59