| /* |
| http://code.google.com/p/inferno-os/source/browse/libbio/bseek.c |
| |
| Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved. |
| Revisions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com). All rights reserved. |
| |
| Permission is hereby granted, free of charge, to any person obtaining a copy |
| of this software and associated documentation files (the "Software"), to deal |
| in the Software without restriction, including without limitation the rights |
| to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
| copies of the Software, and to permit persons to whom the Software is |
| furnished to do so, subject to the following conditions: |
| |
| The above copyright notice and this permission notice shall be included in |
| all copies or substantial portions of the Software. |
| |
| THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
| OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
| THE SOFTWARE. |
| */ |
| |
| #include <u.h> |
| #include <libc.h> |
| #include <bio.h> |
| |
| vlong |
| Bseek(Biobuf *bp, vlong offset, int base) |
| { |
| vlong n, d; |
| int bufsz; |
| |
| #ifndef __MINGW32__ |
| if(sizeof(offset) != sizeof(off_t)) { |
| fprint(2, "Bseek: libbio compiled with %d-byte offset\n", sizeof(off_t)); |
| abort(); |
| } |
| #endif |
| |
| switch(bp->state) { |
| default: |
| fprint(2, "Bseek: unknown state %d\n", bp->state); |
| return Beof; |
| |
| case Bracteof: |
| bp->state = Bractive; |
| bp->icount = 0; |
| bp->gbuf = bp->ebuf; |
| |
| case Bractive: |
| n = offset; |
| if(base == 1) { |
| n += Boffset(bp); |
| base = 0; |
| } |
| |
| /* |
| * try to seek within buffer |
| */ |
| if(base == 0) { |
| d = n - Boffset(bp); |
| bufsz = bp->ebuf - bp->gbuf; |
| if(-bufsz <= d && d <= bufsz){ |
| bp->icount += d; |
| if(d >= 0) { |
| if(bp->icount <= 0) |
| return n; |
| } else { |
| if(bp->ebuf - bp->gbuf >= -bp->icount) |
| return n; |
| } |
| } |
| } |
| |
| /* |
| * reset the buffer |
| */ |
| n = lseek(bp->fid, n, base); |
| bp->icount = 0; |
| bp->gbuf = bp->ebuf; |
| break; |
| |
| case Bwactive: |
| Bflush(bp); |
| n = lseek(bp->fid, offset, base); |
| break; |
| } |
| bp->offset = n; |
| return n; |
| } |