


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.

     _H_e_a_d_e_r _v_e_r_s_i_o_n _n_u_m_b_e_r
     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

     _F_i_l_e_n_a_m_e
     14 bytes of name, zero terminated.

     _C_o_m_p_r_e_s_s_e_d _l_e_n_g_t_h
     Compressed data length, one word.

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

     _T_i_m_e
     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.

     _C_R_C
     One half-word, Cyclic Redundancy Check.

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

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

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

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

     _C_o_m_p_r_e_s_s_e_d _d_a_t_a...
     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



