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Updated the documentation about the overall framework of libisofs

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image production and opportunities to add metadata of other filesystem
types.
This commit is contained in:
Thomas Schmitt 2012-06-07 10:45:09 +02:00
parent 74bc1808a1
commit f39e73d2ce
1 changed files with 26 additions and 0 deletions
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doc/iso_hybrid_fs.txt
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@ -84,6 +84,23 @@ libisofs/ecma119.h at struct ecma119_image.system_area_options and in
libisofs/libisofs.h at call iso_write_opts_set_system_area(). See e.g.
"MIPS Big Endian Volume Header".
libisofs/system_area.h offers an inner API to define partitions for Apple
Partition Map (APM) and for GPT from within the compute_data_blocks methods
of the IsoImageWriter objects (see below). If both get combined, then
APM block size must be 2048. In this case, the partition entries of APM
and GPT overwrite the following bytes of the submitted
Ecma119Image.system_area_data:
0x0000 to 0x0007 by { 0x45, 0x52, 0x08 0x00, 0xeb, 0x02, 0xff, 0xff}
0x0200 to 0x02ff by GPT header block
0x0800 to APM_end by APM blocks (APM_end = 2048*(Num_APM_partitions + 1)
APM_end+1 to 0x7fff by GPT entries
This offers still room for a PC-BIOS MBR which has essentially no-op commands
in its first 8 bytes.
If no GPT is desired, then the bytes after APM_end stay unaltered.
If more modesty with overwriting is needed, then this would have to be caused
by either a specialized system area type or by additional elements of the
inner API for APM and GPT.
The layout of the areas above image_start+16 is defined in function
libisofs/ecma119.c:ecma119_image_new(). This is done by creating and
@ -148,6 +165,15 @@ struct iso_file_section is defined in libisofs/libisofs.h.
IsoImageWriter.free_data() disposes the writer and the JolietNode tree.
Further examples for add-on writers are those created by:
hfsplus_writer_create() is in charge for initial part of an
embedded HFS+ filesystem
hfsplus_tail_writer_create() is in charge for trailing part of HFS+
after the data file content area
gpt_tail_writer_create() is in charge for the backup GPT near the
end of the ISO image
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