ib_seek.c (1670B)
1 /* 2 * Copyright (c) 2003 Gunnar Ritter 3 * 4 * This software is provided 'as-is', without any express or implied 5 * warranty. In no event will the authors be held liable for any damages 6 * arising from the use of this software. 7 * 8 * Permission is granted to anyone to use this software for any purpose, 9 * including commercial applications, and to alter it and redistribute 10 * it freely, subject to the following restrictions: 11 * 12 * 1. The origin of this software must not be misrepresented; you must not 13 * claim that you wrote the original software. If you use this software 14 * in a product, an acknowledgment in the product documentation would be 15 * appreciated but is not required. 16 * 17 * 2. Altered source versions must be plainly marked as such, and must not be 18 * misrepresented as being the original software. 19 * 20 * 3. This notice may not be removed or altered from any source distribution. 21 */ 22 /* Sccsid @(#)ib_seek.c 1.4 (gritter) 5/8/03 */ 23 24 #include <sys/types.h> 25 #include <sys/stat.h> 26 #include <fcntl.h> 27 #include <unistd.h> 28 #include <string.h> 29 #include <errno.h> 30 #include <stdlib.h> 31 32 #include "iblok.h" 33 34 off_t 35 ib_seek(struct iblok *ip, off_t off, int whence) 36 { 37 if (whence == SEEK_CUR) { 38 off = ip->ib_endoff - (ip->ib_end - ip->ib_cur); 39 whence = SEEK_SET; 40 } 41 if (ip->ib_seekable && whence == SEEK_SET && ip->ib_cur && ip->ib_end && 42 off < ip->ib_endoff && 43 off >= ip->ib_endoff - (ip->ib_end - ip->ib_blk)) { 44 ip->ib_cur = ip->ib_end - (ip->ib_endoff - off); 45 return off; 46 } 47 if ((off = lseek(ip->ib_fd, off, whence)) == (off_t)-1) 48 return -1; 49 ip->ib_cur = ip->ib_end = NULL; 50 ip->ib_endoff = off; 51 ip->ib_seekable = 1; 52 return off; 53 }