diff options
| -rw-r--r-- | squashfs-tools/mksquashfs.c | 22 |
1 files changed, 20 insertions, 2 deletions
diff --git a/squashfs-tools/mksquashfs.c b/squashfs-tools/mksquashfs.c index a91fd9e..936ae05 100644 --- a/squashfs-tools/mksquashfs.c +++ b/squashfs-tools/mksquashfs.c @@ -863,11 +863,29 @@ static inline unsigned int get_parent_no(struct dir_info *dir) /* ANDROID CHANGES START*/ #ifdef ANDROID + +/* Round up the passed |n| value to the smallest multiple of 4096 greater or + * equal than |n| and return the 4K-block number for that value. */ +static unsigned long long round_up_block(unsigned long long n) { + const unsigned long long kMapBlockSize = 4096; + return (n + kMapBlockSize - 1) / kMapBlockSize; +} + static inline void write_block_map_entry(char *sub_path, unsigned long long start_block, unsigned long long total_size, char * mount_point, FILE *block_map_file) { if (block_map_file) { - unsigned long long round_start = (start_block + (1 << 12) - 1) >> 12; - unsigned long long round_end = ((start_block + total_size) >> 12) - 1; + /* We assign each 4K block based on what file the first byte of the block + * belongs to. The current file consists of the chunk of bytes in the + * interval [start_block, start_block + total_size), (closed on the left end + * and open on the right end). We then compute the first block whose first + * byte is equal to or greater than start_block as |round_start| and then + * the first block whose first byte is *past* this interval, as + * |round_end + 1|. This means that the blocks that should be assigned to + * the current file are in the interval [round_start, round_end + 1), or + * simply [round_start, round_end]. + */ + unsigned long long round_start = round_up_block(start_block); + unsigned long long round_end = round_up_block(start_block + total_size) - 1; if (round_start && total_size && round_start <= round_end) { fprintf(block_map_file, "/%s", mount_point); if (sub_path[0] != '/') fprintf(block_map_file, "/"); |