From b6c1cf6de79035f58b512f4400db458c8401379a Mon Sep 17 00:00:00 2001 From: The Android Open Source Project Date: Tue, 21 Oct 2008 07:00:00 -0700 Subject: Initial Contribution --- tools/zipalign/README.txt | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) create mode 100644 tools/zipalign/README.txt (limited to 'tools/zipalign/README.txt') diff --git a/tools/zipalign/README.txt b/tools/zipalign/README.txt new file mode 100644 index 0000000..a2e1a5e --- /dev/null +++ b/tools/zipalign/README.txt @@ -0,0 +1,31 @@ +zipalign -- zip archive alignment tool + +usage: zipalign [-f] [-v] infile.zip outfile.zip + + -f : overwrite existing outfile.zip + -v : verbose output + is in bytes, e.g. "4" provides 32-bit alignment + infile.zip is an existing Zip archive + outfile.zip 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. + -- cgit v1.1