ARCFS(5) FILE FORMATS ARCFS(5) NAME ArcFS - Archive file format for the RISC OS ArcFS filesystem CONVENTIONS Strings are given in ASCII with C-style escapes. No ter- minating is present if not explicitly included. Words are 32 bit little-endian numbers. Half words are 16 bit little-endian numbers. This document describes format version 0, for ArcFS minimum versions 0.40 and 1.00, and version 0a, for ArcFS minimum versions 0.58 and 2.17. FORMAT The file consists of a file header, a sequence of archive headers, then a sequence of compressed files. FILE HEADER _F_i_l_e _s_t_r_i_n_g _s_i_g_n_a_t_u_r_e The string "Archive" followed by a zero byte. _H_e_a_d_e_r _l_e_n_g_t_h Length of header info in bytes, one word, multiple of 36. _D_a_t_a _o_f_f_s_e_t Offset, in bytes, into archive at which data starts, one word. _R_e_a_d-_o_n_l_y _v_e_r_s_i_o_n Minimum read-only version required, multiplied by 100, one word. _R_e_a_d-_w_r_i_t_e _v_e_r_s_i_o_n Minimum read--write version required, multiplied by 100, one word. _R_e_s_e_r_v_e_d Reserved for future use, 68 bytes. ARCHIVE HEADER The last header starts at 60+length of headers and ends at 96+length of headers. The format of each header is as fol- lows. _I_n_f_o _b_y_t_e Object information byte, show compression method used: 0x00 end of directory marker Sun Release 4.1 Last change: 1 ARCFS(5) FILE FORMATS ARCFS(5) 0x01 object has been deleted 0x82 stored 0x83 packed 0x88 crunched 0xFF compressed _F_i_l_e _n_a_m_e File name, 11 bytes. _F_u_l_l _l_e_n_g_t_h Original file length, or 0xFFFFFFFF for a directory), one word. _L_o_a_d _a_d_d_r_e_s_s Load address of the file, or 0xFFFFFFdd for a directory), one word. _E_x_e_c _a_d_d_r_e_s_s Exec address of the file, or 0xdddddddd for a directory), one word. File load and execution address may contain a filetype and datestamp as normal. Directories can be date-stamped, the number of centiseconds since the 1st January 1900 when the directory was created are given by &dddddddddd contained in the directory's load and execution addresses as shown above. Archives converted from spark(5) format using ArcConv will have the same full length, compressed length, load address and execute address as they had in the Spark archive. _A_t_t_r_i_b_u_t_e_s Attributes of the file, one word. Contains the number of bits compression for crunch and compress format files and the least significant bytes contains the standard RISC OS information on file access. _C_o_m_p_r_e_s_s_e_d _l_e_n_g_t_h Length of compressed data, or 0xFFFFFFFF for a directory, one word. _I_n_f_o_r_m_a_t_i_o_n _w_o_r_d The top bit (definitively) indicates whether the object is a file or a directory, 0 for a file, 1 for a directory. In the case of a file, the least significant 31 bits show the offset from the start of data at which the file data can be found. In the case of a directory, the least significant 31 bits Sun Release 4.1 Last change: 2 ARCFS(5) FILE FORMATS ARCFS(5) show the offset from the start of headers (96) at which the next object in this directory can be found, the following object being the first in the sub-directory. FORMAT VERSION 0a This archive format is backwards compatible with versions 0.40 and 1.00, the only difference being that there is a block of catalogue information immediately prior to the start of each file's data as described below. Note that this information is there to aid the recovery of most files in the event of archive corruption and is not used by ArcFS. Note, also that Compact and Autocompact in release versions 1.09, 2.02 and 2.11 will compact out the catalogue informa- tion blocks, so try to avoid writing to new archives with old versions of ArcFS. _M_a_r_k_e_r A marker to indicate the start of a file, the string "FileData", not terminated. _I_n_f_o _b_y_t_e One byte, as above. _L_e_a_f _n_a_m_e The file name, 11 bytes. _F_u_l_l _l_e_n_g_t_h One word, as above. _L_o_a_d _a_d_d_r_e_s_s One word, as above. _E_x_e_c _a_d_d_r_e_s_s One word, as above. _A_t_t_r_i_b_u_t_e_s One word, as above. SEE ALSO spark(5), nspark(1) Sun Release 4.1 Last change: 3