blob: 9c7d07e5383321f9078ecf87e59b3b606bbb3b90 [file] [log] [blame]
zipalign -- zip archive alignment tool
usage: zipalign [-f] [-v] <align>
zipalign -c [-v] <align>
-c : check alignment only (does not modify file)
-f : overwrite existing
-v : verbose output
<align> is in bytes, e.g. "4" provides 32-bit alignment is an existing Zip archive will be created
The purpose of zipalign is to ensure that all uncompressed data starts
with a particular alignment relative to the start of the file. This
allows those portions to be accessed directly with mmap() even if they
contain binary data with alignment restrictions.
Some data needs to be word-aligned for easy access, others might benefit
from being page-aligned. The adjustment is made by altering the size of
the "extra" field in the zip Local File Header sections. Existing data
in the "extra" fields may be altered by this process.
Compressed data isn't very useful until it's uncompressed, so there's no
need to adjust its alignment.
Alterations to the archive, such as renaming or deleting entries, will
potentially disrupt the alignment of the modified entry and all later
entries. Files added to an "aligned" archive will not be aligned.
By default, zipalign will not overwrite an existing output file. With the
"-f" flag, an existing file will be overwritten.
You can use the "-c" flag to test whether a zip archive is properly aligned.