Talk:Apk spec

APK v2 package/index terminology

record/block A 512 byte sequence of bytes, a block

h header record/block

d data record/block

e1, e2 EOF markers (two blocks 1024 bytes)

tar archive A tar archive file, consiting of a set of files, a sequence of blocks ending with the eof marker blocks.

tar segment A set of tar records, a sequence of tar records withouth a ending eof marker.

gzip stream A stream is a sequence gzip compressed data, starting with a magic number, headers, body and an ending 8-byte trailer.

[ ... ] A gzip stream containing blocks

concatenate To link togther things in a series or chain. ie. concatenate. Concatenate 3 gzip streams sequentially in a file.

package signature A single file that is a binary signature over the concatenated (control + data) gzip streams

package signature file DigestRSA-PKCS1v15(SHA1( apk-gzip-stream-2 ++ apk-gzip-stream-3), DER)

index signature file DigestRSA-PKCS1v15(SHA1( index-gzip-stream-2), DER)

h A tar header record block

h1 Signature file header, permission 0644, uid 0 and gid 0.

C: checksum The SHA1 hash of the "Control data" gzip stream (gzip stream 2)

APK v2 package layout

Gzip Streams	apk-gzip-stream1	apk-gzip-stream2	apk-gzip-stream-3
Tar	apk-tar-segment-1	apk-tar-segment-2	apk-tarball
Blocks	[h1, d, ...]	[h, d, ...]	[h, d, h, d, ..., e1, e2 ]
Files	Package Signature	Control Data	Package Data

Index v2 layout

Gzip Streams	index-gzip-stream1	index-gzip-stream2
Tar	index-tar-segment-1	index-tar-segment-2
Blocks	[h1, d, ...]	[h, d, ..., d1, d2]
Files	Package Signature	Description and APKINDEX