2 * UCW Library -- Mapping of File Parts
4 * (c) 2003 Martin Mares <mj@ucw.cz>
5 * (c) 2003--2005 Robert Spalek <robert@ucw.cz>
7 * This software may be freely distributed and used according to the terms
8 * of the GNU Lesser General Public License.
23 #define PARTMAP_WINDOW 4096
25 #define PARTMAP_WINDOW 16777216
29 partmap_open(byte *name, int writeable)
31 struct partmap *p = xmalloc_zero(sizeof(struct partmap));
33 p->fd = sh_open(name, writeable ? O_RDWR : O_RDONLY);
35 die("open(%s): %m", name);
36 if ((p->file_size = sh_seek(p->fd, 0, SEEK_END)) < 0)
37 die("lseek(%s): %m", name);
38 p->writeable = writeable;
43 partmap_size(struct partmap *p)
49 partmap_close(struct partmap *p)
52 munmap(p->start_map, p->end_off - p->start_off);
58 partmap_load(struct partmap *p, sh_off_t start, uns size)
61 munmap(p->start_map, p->end_off - p->start_off);
62 sh_off_t end = start + size;
63 sh_off_t win_start = start/PAGE_SIZE * PAGE_SIZE;
64 uns win_len = PARTMAP_WINDOW;
65 if ((sh_off_t) (win_start+win_len) > p->file_size)
66 win_len = ALIGN(p->file_size - win_start, PAGE_SIZE);
67 if ((sh_off_t) (win_start+win_len) < end)
68 die("partmap_map: Window is too small for mapping %d bytes", size);
69 p->start_map = sh_mmap(NULL, win_len, p->writeable ? (PROT_READ | PROT_WRITE) : PROT_READ, MAP_SHARED, p->fd, win_start);
70 if (p->start_map == MAP_FAILED)
71 die("mmap failed at position %Ld: %m", (long long)win_start);
72 p->start_off = win_start;
73 p->end_off = win_start+win_len;
77 int main(int argc, char **argv)
79 struct partmap *p = partmap_open(argv[1], 0);
80 uns l = partmap_size(p);
83 putchar(*(char *)partmap_map(p, i, 1));