diff options
Diffstat (limited to 'docs/LAR.md')
| -rw-r--r-- | docs/LAR.md | 87 |
1 files changed, 0 insertions, 87 deletions
diff --git a/docs/LAR.md b/docs/LAR.md deleted file mode 100644 index 457b076f9a..0000000000 --- a/docs/LAR.md +++ /dev/null @@ -1,87 +0,0 @@ -LAR is a simple archive format to pack multiple lua source files and arbitrary other resources into a single file. - - -# Format Specification - -A LAR archive file is divided into two parts: the payload and the index lookup table. -All segments of the archive are 4 Byte aligned to ease reading and processing of the format. -All integers are stored in network byte order, so an implementation has to use htonl() and htons() to properly read them. - -Schema: - - <payload: - <member: - <N*4 bytes: path of file #1> - <N*4 bytes: data of file #1> - > - - <member: - <N*4 bytes: path of file #2> - <N*4 bytes: data of file #2> - > - - ... - - <member: - <N*4 bytes: path of file #N> - <N*4 bytes: data of file #N> - > - > - - <index table: - <entry: - <uint32: offset for path of file #1> <uint32: length for path of file #1> - <uint32: offset for data of file #1> <uint32: length for data of file #1> - <uint16: type of file #1> <uint16: flags of file #1> - > - - <entry: - <uint32: offset for path of file #2> <uint32: length for path of file #2> - <uint32: offset for data of file #2> <uint32: length for data of file #2> - <uint16: type of file #2> <uint16: flags of file #2> - > - - ... - - <entry: - <uint32: offset for path of file #N> <uint32: length for path of file #N> - <uint32: offset for data of file #N> <uint32: length for data of file #N> - <uint16: type of file #N> <uint16: flags of file #N> - > - > - - <uint32: offset for begin of index table> - - - -# Processing - -In order to process an LAR archive, an implementation would have to do the following steps: - -## Read Index - -1. Locate and open the archive file -1. Seek to end of file - 4 bytes -1. Read 32bit index offset and swap from network to native byte order -1. Seek to index offset, calculate index length: filesize - index offset - 4 -1. Initialize a linked list for index table entries -1. Read each index entry until the index length is reached, read and byteswap 4 * 32bit int and 2 * 16bit int -1. Seek to begin of file - -## Read Member - -1. Read the archive index -1. Iterate through the linked index list, perform the following steps for each entry -1. Seek to the specified file path offset -1. Read as much bytes as specified in the file path length into a buffer -1. Compare the contents of the buffer against the path of the searched member -1. If buffer and searched path are equal, seek to the specified file data offset -1. Read data until the file data length is reached, return -1. Select the next index table entry and repeat from step 3, if there is no next entry then return - -# Reference implementation - -A reference implementation can be found here: -http://luci.subsignal.org/trac/browser/luci/trunk/contrib/lar - -The lar.pl script is a simple packer for LAR archives and cli.c provides a utility to list and dump packed LAR archives. |