


SPARK(5)()        MISC. REFERENCE MANUAL PAGES         SPARK(5)()



NAME
     spark - Archive file format for RISC OS version  of  the  PC
     archiver Arc

CONVENTIONS
     Strings are given in ASCII with  C-style  escapes.  No  ter-
     minating   is present if not explicitily included.

     Words are 32 bit little-endian numbers.

     Half words are 16 bit little-endian numbers.


FORMAT
     An archive file consists of a sequence  of  archive  marker,
     archive  header  and file data, ie. marker1, header1, data1,
     marker2, header2, data2, etc.  The archive marker is a  sin-
     gle  byte  of value 0x1a (26).  The archive finishes with an
     archive marker followed by a zero byte.

     Header version number
     This tells you how the file data  is  stored  and  how  many
     bytes  there  are  in the header. The header version numbers
     for the PC, are detailed below. An Archimedes header version
     number is identical to the corresponding PC number except it
     has bit 7 set.
          1    Old style, no compression
          2    New style, no compression
          3    Compression of repeated characters only (RLE)
          4    As 3 plus Huffman Squeezing
          5    Lempel-Ziv packing of repeated strings (old style)
          6    Lempel-Ziv packing of repeated strings (new style)
          7    Lempel-Ziv Welch packing with improved hash function
          8    Dynamic Lempel-Ziv packing with adaptive reset
          9    PKARC style squashing
          127  Un*x compression

     Filename
     14 bytes of name, zero terminated.

     Compressed length
     Compressed data length, one word.

     Date
     One half-word, date.
          year = (date >> 9) & 0x7f;
          month = (date >> 5) & 0x0f;
          day = date & 0x1f;

     Time
     One half-word, time.
          hour = (time >> 11) & 0x1f;



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SPARK(5)()        MISC. REFERENCE MANUAL PAGES         SPARK(5)()



          minute = (time >> 5)  & 0x3f;
          second = (time & 0x1f) * 2;

     The time and date fields are always filled in. If  the  file
     has  a  load  and  exec address, these are the time and date
     when the file was added to the archive otherwise,  they  are
     derived from the Archimedes datestamp. In all extract opera-
     tions on Archimedes format archives,  the  contents  of  the
     load and exec fields take precedence.

     CRC
     One half-word, Cyclic Redundancy Check.

     Original file length
     Original file length, one word, only present if header  type
     greater than 1.

     Load address
     Load address of the file, one word, only present if bit-7 of
     the header version number is set.

     Exec address
     Exec address of the file, one word, only present if bit-7 of
     the header version number is set.

     Attributes
     Attributes of the file, one word, only present if  bit-7  of
     the header version number is set.

     Compressed data...
     Directories are stored  as  non-compressed  archives  within
     archives, ie. their load address & 0xffffff00=0xfffddc.


COMPATIBILITY
     PC and Archimedes formats may be mixed in  one  archive  for
     use on the Archimedes.


SEE ALSO
     arcfs(5), nspark(1)














Sun Release 4.1           Last change:                          2



