diff options
Diffstat (limited to 'contrib/syslinux-4.02/core/fs/getfssec.c')
| -rw-r--r-- | contrib/syslinux-4.02/core/fs/getfssec.c | 194 |
1 files changed, 194 insertions, 0 deletions
diff --git a/contrib/syslinux-4.02/core/fs/getfssec.c b/contrib/syslinux-4.02/core/fs/getfssec.c new file mode 100644 index 0000000..e099b64 --- /dev/null +++ b/contrib/syslinux-4.02/core/fs/getfssec.c @@ -0,0 +1,194 @@ +/* ----------------------------------------------------------------------- * + * + * Copyright 2010 Intel Corporation; author: H. Peter Anvin + * + * 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. + * + * ----------------------------------------------------------------------- */ + +/* + * getfssec.c + * + * Generic getfssec implementation for disk-based filesystems, which + * support the next_extent() method. + * + * The expected semantics of next_extent are as follows: + * + * The second argument will contain the initial sector number to be + * mapped. The routine is expected to populate + * inode->next_extent.pstart and inode->next_extent.len (the caller + * will store the initial sector number into inode->next_extent.lstart + * on return.) + * + * If inode->next_extent.len != 0 on entry then the routine is allowed + * to assume inode->next_extent contains valid data from the previous + * usage, which can be used for optimization purposes. + * + * If the filesystem can map the entire file as a single extent + * (e.g. iso9660), then the filesystem can simply insert the extent + * information into inode->next_extent at searchdir/iget time, and leave + * next_extent() as NULL. + * + * Note: the filesystem driver is not required to do extent coalescing, + * if that is difficult to do; this routine will perform extent lookahead + * and coalescing. + */ + +#include <dprintf.h> +#include <minmax.h> +#include "fs.h" + +static inline sector_t next_psector(sector_t psector, uint32_t skip) +{ + if (EXTENT_SPECIAL(psector)) + return psector; + else + return psector + skip; +} + +static inline sector_t next_pstart(const struct extent *e) +{ + return next_psector(e->pstart, e->len); +} + + +static void get_next_extent(struct inode *inode) +{ + /* The logical start address that we care about... */ + uint32_t lstart = inode->this_extent.lstart + inode->this_extent.len; + + if (inode->fs->fs_ops->next_extent(inode, lstart)) + inode->next_extent.len = 0; /* ERROR */ + inode->next_extent.lstart = lstart; + + dprintf("Extent: inode %p @ %u start %llu len %u\n", + inode, inode->next_extent.lstart, + inode->next_extent.pstart, inode->next_extent.len); +} + +uint32_t generic_getfssec(struct file *file, char *buf, + int sectors, bool *have_more) +{ + struct inode *inode = file->inode; + struct fs_info *fs = file->fs; + struct disk *disk = fs->fs_dev->disk; + uint32_t bytes_read = 0; + uint32_t bytes_left = inode->size - file->offset; + uint32_t sectors_left = + (bytes_left + SECTOR_SIZE(fs) - 1) >> SECTOR_SHIFT(fs); + uint32_t lsector; + + if (sectors > sectors_left) + sectors = sectors_left; + + if (!sectors) + return 0; + + lsector = file->offset >> SECTOR_SHIFT(fs); + dprintf("Offset: %u lsector: %u\n", file->offset, lsector); + + if (lsector < inode->this_extent.lstart || + lsector >= inode->this_extent.lstart + inode->this_extent.len) { + /* inode->this_extent unusable, maybe next_extent is... */ + inode->this_extent = inode->next_extent; + } + + if (lsector < inode->this_extent.lstart || + lsector >= inode->this_extent.lstart + inode->this_extent.len) { + /* Still nothing useful... */ + inode->this_extent.lstart = lsector; + inode->this_extent.len = 0; + } else { + /* We have some usable information */ + uint32_t delta = lsector - inode->this_extent.lstart; + inode->this_extent.lstart = lsector; + inode->this_extent.len -= delta; + inode->this_extent.pstart + = next_psector(inode->this_extent.pstart, delta); + } + + dprintf("this_extent: lstart %u pstart %llu len %u\n", + inode->this_extent.lstart, + inode->this_extent.pstart, + inode->this_extent.len); + + while (sectors) { + uint32_t chunk; + size_t len; + + while (sectors > inode->this_extent.len) { + if (!inode->next_extent.len || + inode->next_extent.lstart != + inode->this_extent.lstart + inode->this_extent.len) + get_next_extent(inode); + + if (!inode->this_extent.len) { + /* Doesn't matter if it's contiguous... */ + inode->this_extent = inode->next_extent; + if (!inode->next_extent.len) { + sectors = 0; /* Failed to get anything... we're dead */ + break; + } + } else if (inode->next_extent.len && + inode->next_extent.pstart == next_pstart(&inode->this_extent)) { + /* Coalesce extents and loop */ + inode->this_extent.len += inode->next_extent.len; + } else { + /* Discontiguous extents */ + break; + } + } + + dprintf("this_extent: lstart %u pstart %llu len %u\n", + inode->this_extent.lstart, + inode->this_extent.pstart, + inode->this_extent.len); + + chunk = min(sectors, inode->this_extent.len); + len = chunk << SECTOR_SHIFT(fs); + + dprintf(" I/O: inode %p @ %u start %llu len %u\n", + inode, inode->this_extent.lstart, + inode->this_extent.pstart, chunk); + + if (inode->this_extent.pstart == EXTENT_ZERO) { + memset(buf, 0, len); + } else { + disk->rdwr_sectors(disk, buf, inode->this_extent.pstart, chunk, 0); + inode->this_extent.pstart += chunk; + } + + buf += len; + sectors -= chunk; + bytes_read += len; + inode->this_extent.lstart += chunk; + inode->this_extent.len -= chunk; + } + + bytes_read = min(bytes_read, bytes_left); + file->offset += bytes_read; + + if (have_more) + *have_more = bytes_read < bytes_left; + + return bytes_read; +} |