README.txt revision 88b607994a148f4af5bffee163e39ce8296750c6 
1zipalign -- zip archive alignment tool
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3usage: zipalign [-f] [-v] <align> infile.zip outfile.zip
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5  -f : overwrite existing outfile.zip
6  -v : verbose output
7  <align> is in bytes, e.g. "4" provides 32-bit alignment
8  infile.zip is an existing Zip archive
9  outfile.zip will be created
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12The purpose of zipalign is to ensure that all uncompressed data starts
13with a particular alignment relative to the start of the file.  This
14allows those portions to be accessed directly with mmap() even if they
15contain binary data with alignment restrictions.
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17Some data needs to be word-aligned for easy access, others might benefit
18from being page-aligned.  The adjustment is made by altering the size of
19the "extra" field in the zip Local File Header sections.  Existing data
20in the "extra" fields may be altered by this process.
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22Compressed data isn't very useful until it's uncompressed, so there's no
23need to adjust its alignment.
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25Alterations to the archive, such as renaming or deleting entries, will
26potentially disrupt the alignment of the modified entry and all later
27entries.  Files added to an "aligned" archive will not be aligned.
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29By default, zipalign will not overwrite an existing output file.  With the
30"-f" flag, an existing file will be overwritten.
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