iso9660文件格式 VC/MFC / Visual C 资源

iso9660文件格式
bravebarbarian（野蛮人）2002-10-06 21:28:07 在 VC/MFC / Visual C++ 资源 提问
谁能帮我找到iso9660文件格式的资料.谢谢. 问题点数：100、回复次数：4Top
ch21st（www.blanksoft.com）回复于 2002-10-09 11:51:54 得分 100
1.   Introduction
We   weren‘t   sure   about   it   a   few   years   ago,   but   by   now   it   should   be   clear   to   everyone   that   CD-ROM‘s   are   here   to   stay.   Most   PC‘s   are   equipped   with   CD-ROM   readers,   and   most   major   PC   software   packages   are   being   distributed   on   CD-ROM‘s.
Under   DOS   (and   Windows,   which   uses   the   DOS   file   system)   files   are   written   to   both   hard   and   floppy   disks   with   a   so-called   FAT   (File   Allocation   Table)   file   system.
Files   on   a   CD-ROM,   however,   are   written   to   a   different   standard,   called   ISO9660.   ISO9660   is   rather   complex   and   poorly   written,   and   obviously   contains   a   number   of   diplomatic   compromises   among   advocates   of   DOS,   UNIX,   MVS   and   perhaps   other   operating   systems.
The   simplified   version   presented   here   includes   only   features   that   would   normally   be   found   on   a   CD-ROM   to   be   used   in   a   DOS   system   and   which   are   supported   by   the   Microsoft   MS-DOS   CD-ROM   Extensions   (MSCDEX).   It   is   based   on   ISO9660,   on   certain   documents   regarding   MSCDEX   (version   2.10),   and   on   the   contents   of   some   actual   CD-ROM‘s.
Where   a   field   has   a   specific   value   on   a   CD-ROM   to   be   used   with   DOS,   that   value   is   given   in   this   document.   However,   in   some   cases   a   brief   description   of   values   for   use   with   other   operating   systems   is   given   in   square   brackets.
ISO9660   makes   provisions   for   sets   of   CD-ROM‘s,   and   apparently   even   permits   a   file   system   to   span   more   than   one   CD-ROM.   However,   this   feature   is   not   supported   by   MSCDEX.
2.   Files
The   directory   structure   on   a   CD-ROM   is   almost   exactly   like   that   on   a   DOS   floppy   or   hard   disk.   (It   is   presumed   that   the   reader   of   this   document   is   reasonably   familiar   with   the   DOS   file   system.)   For   this   reason,   DOS   and   Windows   applications   can   read   files   from   a   CD-ROM   just   as   they   would   from   a   floppy   or   hard   disk.
There   are   only   a   few   differences,   which   do   not   affect   most   applications:
The   root   directory   contains   the   notorious   "."   and   ".."   entries,   just   like   any   other   directory.
There   is   no   limit,   other   than   disk   capacity,   to   the   size   of   the   root   directory.
The   depth   of   directory   nesting   is   limited   to   eight   levels,   including   the   root.   For   example,   if   drive   E:   contains   a   CD-ROM,   a   file   such   as   E:\D2\D3\D4\D5\D6\D7\D8\FOO.TXT   is   permitted   but   E:\D2\D3\D4\D5\D6\D7\D8\D9\FOO.TXT   is   not.
If   a   CD-ROM   is   to   be   used   by   a   DOS   system,   file   names   and   extensions   must   be   limited   to   eight   and   three   characters,   respectively,   even   though   ISO9660   permits   longer   names   and   extensions.
ISO9660   permits   only   capital   letters,   digits   and   underscores   in   a   file   or   directory   name   or   extension,   but   DOS   also   permits   a   number   of   other   punctuation   marks.
ISO9660   permits   a   file   to   have   an   extension   but   not   a   name,   but   DOS   does   not.
DOS   permits   a   directory   to   have   an   extension,   but   ISO9660   does   not.
Directories   on   a   CD-ROM   are   always   sorted,   as   described   below.
Of   course,   neither   DOS,   nor   UNIX,   nor   any   other   operating   system   can   WRITE   files   to   a   CD-ROM   as   it   would   to   a   floppy   or   hard   disk,   because   a   CD-ROM   is   not   rewritable.   Files   must   be   written   to   the   CD-ROM   by   a   special   program   with   special   hardware.
3.   Sectors
The   information   on   a   CD-ROM   is   divided   into   sectors,   which   are   numbered   consecutively,   starting   with   zero.   There   are   no   gaps   in   the   numbering.
Each   sector   contains   2048   8-bit   bytes.   (ISO9660   apparently   permits   other   sector   sizes,   but   the   2048-byte   size   seems   to   be   universal.)
When   a   number   of   sectors   are   to   be   read   from   the   CD-ROM,   they   should   be   read   in   order   of   increasing   sector   number,   if   possible,   since   that   is   the   order   in   which   they   pass   under   the   read   head   as   the   CD-ROM   rotates.   Most   implementations   arrange   the   information   so   sectors   will   be   read   in   this   order   for   typical   file   operations,   although   ISO9660   does   not   require   this   in   all   cases.
The   order   of   bytes   within   a   sector   is   considered   to   be   the   order   in   which   they   appear   when   read   into   memory;   i.e.,   the   "first"   bytes   are   read   into   the   lowest   memory   addresses.   This   is   also   the   order   used   in   this   document;   i.e.,   the   "first"   bytes   in   any   list   appear   at   the   top   of   the   list.
4.   Character   Sets
Names   and   extensions   of   files   and   directories,   the   volume   name,   and   some   other   names   are   expressed   in   standard   ASCII   character   codes   (although   ISO9660   does   not   use   the   name   ASCII).   According   to   ISO9660,   only   capital   letters,   digits,   and   underscores   are   permitted.   However,   DOS   permits   some   other   punctuation   marks,   which   are   sometimes   found   on   CD-ROM‘s,   in   apparent   defiance   of   ISO9660.
MSCDEX   does   offer   support   for   the   kanji   (Japanese)   character   set.   However,   this   document   does   not   cover   kanji.
5.   Sorting   Names   or   Extensions
Where   ISO9660   requires   file   or   directory   names   or   extensions   to   be   sorted,   the   usual   ASCII   collating   sequence   is   used.   That   is,   two   different   names   or   extensions   are   compared   as   follows:
ASCII   blanks   (32)   are   added   to   the   right   end   of   the   shorter   name   or   extension,   if   necessary,   to   make   it   as   long   as   the   longer   name   or   extension.
The   first   (leftmost)   position   in   which   the   names   or   extensions   are   not   identical   determines   the   order.   The   name   or   extension   with   the   lower   ASCII   code   in   that   position   appears   first   in   the   sorted   order.
6.   Multiple-Byte   Values
A   16-bit   numeric   value   (usually   called   a   word)   may   be   represented   on   a   CD-ROM   in   any   of   three   ways:
Little   Endian   Word:
The   value   occupies   two   consecutive   bytes,   with   the   less   significant   byte   first.
Big   Endian   Word:
The   value   occupies   two   consecutive   bytes,   with   the   more   significant   byte   first.
Both   Endian   Word:
The   value   occupies   FOUR   consecutive   bytes;   the   first   and   second   bytes   contain   the   value   expressed   as   a   little   endian   word,   and   the   third   and   fourth   bytes   contain   the   same   value   expressed   as   a   big   endian   word.
A   32-bit   numeric   value   (usually   called   a   double   word)   may   be   represented   on   a   CD-ROM   in   any   of   three   ways:
Little   Endian   Double   Word:
The   value   occupies   four   consecutive   bytes,   with   the   least   significant   byte   first   and   the   other   bytes   in   order   of   increasing   significance.
Big   Endian   Double   Word:
The   value   occupies   four   consecutive   bytes,   with   the   most   significant   first   and   the   other   bytes   in   order   of   decreasing   significance.
Both   Endian   Double   Word:
The   value   occupies   EIGHT   consecutive   bytes;   the   first   four   bytes   contain   the   value   expressed   as   a   little   endian   double   word,   and   the   last   four   bytes   contain   the   same   value   expressed   as   a   big   endian   double   word.
7.   The   First   Sixteen   Sectors   are   Empty
The   first   sixteen   sectors   (sector   numbers   0   to   15,   inclusive)   contain   nothing   but   zeros.   ISO9660   does   not   define   the   contents   of   these   sectors,   but   for   DOS   they   are   apparently   always   written   as   zeros.   They   are   apparently   reserved   for   use   by   systems   that   can   be   booted   from   a   CD-ROM.
8.   The   Volume   Descriptors
Sector   16   and   a   few   of   the   following   sectors   contain   a   series   of   volume   descriptors.   There   are   several   kinds   of   volume   descriptor,   but   only   two   are   normally   used   with   DOS.   Each   volume   descriptor   occupies   exactly   one   sector.
The   last   volume   descriptors   in   the   series   are   one   or   more   Volume   Descriptor   Set   Terminators.   The   first   seven   bytes   of   a   Volume   Descriptor   Set   Terminator   are   255,   67,   68,   48,   48,   49   and   1,   respectively.   The   other   2041   bytes   are   zeros.   (The   middle   bytes   are   the   ASCII   codes   for   the   characters   CD001.)
The   only   volume   descriptor   of   real   interest   under   DOS   is   the   Primary   Volume   Descriptor.   There   must   be   at   least   one,   and   there   is   usually   only   one.   However,   some   CD-ROM‘s   have   two   or   more   identical   Primary   Volume   Descriptors.   The   contents   of   a   Primary   Volume   Descriptor   are   as   follows:
length
in   bytes     contents
--------     ---------------------------------------------------------
1             1
6             67,   68,   48,   48,   49   and   1,   respectively   (same   as   Volume
Descriptor   Set   Terminator)
1             0
32             system   identifier
32             volume   identifier
8             zeros
8             total   number   of   sectors,   as   a   both   endian   double   word
32             zeros
4             1,   as   a   both   endian   word   [volume   set   size]
4             1,   as   a   both   endian   word   [volume   sequence   number]
4             2048   (the   sector   size),   as   a   both   endian   word
8             path   table   length   in   bytes,   as   a   both   endian   double   word
4             number   of   first   sector   in   first   little   endian   path   table,
as   a   little   endian   double   word
4             number   of   first   sector   in   second   little   endian   path   table,
as   a   little   endian   double   word,   or   zero   if   there   is   no
second   little   endian   path   table
4             number   of   first   sector   in   first   big   endian   path   table,
as   a   big   endian   double   word
4             number   of   first   sector   in   second   big   endian   path   table,
as   a   big   endian   double   word,   or   zero   if   there   is   no
second   big   endian   path   table
34             root   directory   record,   as   described   below
128             volume   set   identifier
128             publisher   identifier
128             data   preparer   identifier
128             application   identifier
37             copyright   file   identifier
37             abstract   file   identifier
37             bibliographical   file   identifier
17             date   and   time   of   volume   creation
17             date   and   time   of   most   recent   modification
17             date   and   time   when   volume   expires
17             date   and   time   when   volume   is   effective
1             1
1             0
512             reserved   for   application   use   (usually   zeros)
653             zeros
The   first   11   characters   of   the   volume   identifier   are   returned   as   the   volume   identifier   by   standard   DOS   system   calls   and   utilities.
Other   identifiers   are   not   used   by   DOS,   and   may   be   filled   with   ASCII   blanks   (32).
Each   date   and   time   field   is   of   the   following   form:
length
in   bytes     contents
--------     ---------------------------------------------------------
4             year,   as   four   ASCII   digits
2             month,   as   two   ASCII   digits,   where
01=January,   02=February,   etc.
2             day   of   month,   as   two   ASCII   digits,   in   the   range
from   01   to   31
2             hour,   as   two   ASCII   digits,   in   the   range   from   00   to   23
2             minute,   as   two   ASCII   digits,   in   the   range   from   00   to   59
2             second,   as   two   ASCII   digits,   in   the   range   from   00   to   59
2             hundredths   of   a   second,   as   two   ASCII   digits,   in   the   range
from   00   to   99
1             offset   from   Greenwich   Mean   Time,   in   15-minute   intervals,
as   a   twos   complement   signed   number,   positive   for   time
zones   east   of   Greenwich,   and   negative   for   time   zones
west   of   Greenwich
If   the   date   and   time   are   not   specified,   the   first   16   bytes   are   all   ASCII   zeros   (48),   and   the   last   byte   is   zero.
Other   kinds   of   Volume   Descriptors   (which   are   normally   ignored   by   DOS)   have   the   following   format:
length
in   bytes     contents
--------     ---------------------------------------------------------
1             neither   1   nor   255
6             67,   68,   48,   48,   49   and   1,   respectively   (same   as   Volume
Descriptor   Set   Terminator)
2041           other   things
9.   Path   Tables
The   path   tables   normally   come   right   after   the   volume   descriptors.   However,   ISO9660   merely   requires   that   each   path   table   begin   in   the   sector   specified   by   the   Primary   Volume   Descriptor.
The   path   tables   are   actually   redundant,   since   all   of   the   information   contained   in   them   is   also   stored   elsewhere   on   the   CD-ROM.   However,   their   use   can   make   directory   searches   much   faster.
There   are   two   kinds   of   path   table   --   a   little   endian   path   table,   in   which   multiple-byte   values   are   stored   in   little   endian   order,   and   a   big   endian   path   table,   in   which   multiple-byte   values   are   stored   in   big   endian   order.   The   two   kinds   of   path   tables   are   identical   in   every   other   way.
A   path   table   contains   one   record   for   each   directory   on   the   CD-ROM   (including   the   root   directory).   The   format   of   a   record   is   as   follows:
length
in   bytes     contents
--------     ---------------------------------------------------------
1             N,   the   name   length   (or   1   for   the   root   directory)
1             0   [number   of   sectors   in   extended   attribute   record]
4             number   of   the   first   sector   in   the   directory,   as   a
double   word
2             number   of   record   for   parent   directory   (or   1   for   the   root
directory),   as   a   word;   the   first   record   is   number   1,
the   second   record   is   number   2,   etc.
N             name   (or   0   for   the   root   directory)
0   or   1       padding   byte:   if   N   is   odd,   this   field   contains   a   zero;   if
N   is   even,   this   field   is   omitted
According   to   ISO9660,   a   directory   name   consists   of   at   least   one   and   not   more   than   31   capital   letters,   digits   and   underscores.   For   DOS   the   upper   limit   is   eight   characters.
A   path   table   occupies   as   many   consecutive   sectors   as   may   be   required   to   hold   all   its   records.   The   first   record   always   begins   in   the   first   byte   of   the   first   sector.   Except   for   the   single   byte   described   above,   no   padding   is   used   between   records;   hence   the   last   record   in   a   sector   is   usually   continued   in   the   next   following   sector.   The   unused   part   of   the   last   sector   is   filled   with   zeros.
The   records   in   a   path   table   are   arranged   in   a   precisely   specified   order.   For   this   purpose,   each   directory   has   an   associated   number   called   its   level.   The   level   of   the   root   directory   is   1.   The   level   of   each   other   directory   is   one   greater   than   the   level   of   its   parent.   As   noted   above,   ISO9660   does   not   permit   levels   greater   than   8.
The   relative   positions   of   any   two   records   are   determined   as   follows:
If   the   levels   are   different,   the   directory   with   the   lower   level   appears   first.   In   particular,   this   implies   that   the   root   directory   is   always   represented   by   the   first   record   in   the   table,   because   it   is   the   only   directory   with   level   1.
If   the   levels   are   identical,   but   the   directories   have   different   parents,   then   the   directories   are   in   the   same   relative   positions   as   their   parents.
Directories   with   the   same   level   and   the   same   parent   are   arranged   in   the   order   obtained   by   sorting   on   their   names,   as   described   in   Section   5.
10.   Directories
A   directory   consists   of   a   series   of   directory   records   in   one   or   more   consecutive   sectors.   However,   unlike   path   records,   directory   records   may   not   straddle   sector   boundaries.   There   may   be   unused   space   at   the   end   of   each   sector,   which   is   filled   with   zeros.
Each   directory   record   represents   a   file   or   directory.   Its   format   is   as   follows:
length
in   bytes     contents
--------     ---------------------------------------------------------
1             R,   the   number   of   bytes   in   the   record   (which   must   be   even)
1             0   [number   of   sectors   in   extended   attribute   record]
8             number   of   the   first   sector   of   file   data   or   directory
(zero   for   an   empty   file),   as   a   both   endian   double   word
8             number   of   bytes   of   file   data   or   length   of   directory,
excluding   the   extended   attribute   record,
as   a   both   endian   double   word
1             number   of   years   since   1900
1             month,   where   1=January,   2=February,   etc.
1             day   of   month,   in   the   range   from   1   to   31
1             hour,   in   the   range   from   0   to   23
1             minute,   in   the   range   from   0   to   59
1             second,   in   the   range   from   0   to   59
(for   DOS   this   is   always   an   even   number)
1             offset   from   Greenwich   Mean   Time,   in   15-minute   intervals,
as   a   twos   complement   signed   number,   positive   for   time
zones   east   of   Greenwich,   and   negative   for   time   zones
west   of   Greenwich   (DOS   ignores   this   field)
1             flags,   with   bits   as   follows:
bit           value
------     ------------------------------------------
0   (LS)     0   for   a   norma1   file,   1   for   a   hidden   file
1               0   for   a   file,   1   for   a   directory
2               0   [1   for   an   associated   file]
3               0   [1   for   record   format   specified]
4               0   [1   for   permissions   specified]
5               0
6               0
7   (MS)     0   [1   if   not   the   final   record   for   the   file]
1             0   [file   unit   size   for   an   interleaved   file]
1             0   [interleave   gap   size   for   an   interleaved   file]
4             1,   as   a   both   endian   word   [volume   sequence   number]
1             N,   the   identifier   length
N             identifier
P             padding   byte:   if   N   is   even,   P   =   1   and   this   field   contains
a   zero;   if   N   is   odd,   P   =   0   and   this   field   is   omitted
R-33-N-P       unspecified   field   for   system   use;   must   contain   an   even
number   of   bytes
The   length   of   a   directory   includes   the   unused   space,   if   any,   at   the   ends   of   sectors.   Hence   it   is   always   an   exact   multiple   of   2048   (the   sector   size).   Since   every   directory,   even   a   nominally   empty   one,   contains   at   least   two   records,   the   length   of   a   directory   is   never   zero.
All   fields   in   the   first   record   (sometimes   called   the   "."   record)   refer   to   the   directory   itself,   except   that   the   identifier   length   is   1,   and   the   identifier   is   zero.   The   root   directory   record   in   the   Primary   Volume   Descriptor   also   has   this   format.
All   fields   in   the   second   record   (sometimes   called   the   ".."   record)   refer   to   the   parent   directory,   except   that   the   identifier   length   is   1,   and   the   identifier   is   1.   The   second   record   in   the   root   directory   refers   to   the   root   directory.
The   identifier   for   a   subdirectory   is   its   name.   The   identifier   for   a   file   consists   of   the   following   fields,   in   the   order   given:
The   name,   consisting   of   the   ASCII   codes   for   at   least   one   and   not   more   than   eight   capital   letters,   digits   and   underscores.
If   there   is   an   extension,   the   ASCII   code   for   a   period   (46).   If   there   is   no   extension,   this   field   is   omitted.
The   extension,   consisting   of   the   ASCII   codes   for   not   more   than   three   capital   letters,   digits   and   underscores.   If   there   is   no   extension,   this   field   is   omitted.
The   ASCII   code   for   a   semicolon   (59).
The   ASCII   code   for   1   (49).   [On   other   systems,   this   is   the   version   number,   consisting   of   the   ASCII   codes   for   a   sequence   of   digits   representing   a   number   between   1   and   32767,   inclusive.]
Some   implementations   for   DOS   omit   (4)   and   (5),   and   some   use   punctuation   marks   other   than   underscores   in   file   names   and   extensions.
Directory   records   other   than   the   first   two   are   sorted   as   follows:
Records   are   sorted   by   name,   as   described   above.
Every   series   of   records   with   the   same   name   is   sorted   by   extension,   as   described   above.   For   this   purpose,   a   record   without   an   extension   is   sorted   as   though   its   extension   consisted   of   ASCII   blanks   (32).
[On   other   systems,   every   series   of   records   with   the   same   name   and   extension   is   sorted   in   order   of   decreasing   version   number.]
[On   other   systems,   two   records   with   the   same   name,   extension   and   version   number   are   permitted,   if   the   first   record   is   an   associated   file.]