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<section><date> 20. July 2002 </date>
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<h2> ZZIP API extras </h2> The check/init API description.
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The next requests circulated around other file-extensions to
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automagically look inside filetypes that have zip-format too but
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carry other fileextensions - most famous might be the ".PK3"
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files of ID's Quake game. There have been a number of these
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requests and in a lot of cases it dawned to me that those guys
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may have overlooked the zzip_dir_open functions to travel
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through documents of zipformat under any name - that is that the
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"magic" was not actually needed but they just wanted to read
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files in zipformat with the zziplib.
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Other requests circulated around encryption but I did reject
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those bluntly, always. Instead there have been always examples
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for doing some obfuscation around the zip-format so that the
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stock zip/unzip tools do not recognize them but a game
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software developer can pack/unpack his AI scripts and bitmaps
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into such a zipformat-like file.
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After some dead-end patches (being shipped along with the
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zziplib as configure-time compile-options - greetings to
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Lutz Sammer and Andreas Schiffler), the general approach
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of _ext_io came up, and finally implemented (greetings go
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to Mike Nordell). The _open()-calls do now each have a
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cousin of _open_ext_io() with two/three additional arguments
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being a set of extensions to loop through our magic testing,
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a callback-handler plugin-table for obfuscation-means,
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and (often) a bit-mask for extra-options - this bitmask even
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has "PREFERZIP" and "ONLYZIP" options to skip the real-file
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test magic in those <code>zzip_*open</code> functions.
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<table cellpadding=10 width=100%><tr><td><table border=1 width=100%>
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<tr><td width=50%> zzip_open(name,flags) </td>
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<td width=50%> zzip_open_ext_io(name,flags,mode,ext,io) </td></tr>
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<tr><td width=50%> zzip_opendir(name) </td>
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<td width=50%> zzip_opendir_ext_io(name,mode,ext,io) </td></tr>
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<tr><td width=50%> zzip_dir_open(name,errp) </td>
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<td width=50%> zzip_dir_open_ext_io(name,errp,ext,io) </td></tr>
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<tr><td width=50%> zzip_dir_fdopen(fd,errp) </td>
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<td width=50%> zzip_dir_fdopen_ext_io(fd,errp,ext,io) </td></tr>
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<tr><td width=50%> zzip_file_open(dir,name,mode) </td>
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<td width=50%> zzip_file_open_ext_io(dir,name,mode,ext,io) </td></tr>
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</table></td></tr></table>
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Oh, and note that the mode,ext,io extras are memorized
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in the respecitive ZZIP_DIR handle attached, so each
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of the other calls like <code>zzip_file_open()</code>
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and <code>zzip_read()</code> will be using them. There
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are a few helper routines to help setup a new io-plugin
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where the init_io will currently just memcopy the
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default_io entries into the user-supplied plugin-struct.
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<table cellpadding=10 width=100%><tr><td><table border=1 width=100%>
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<tr><td width=50%> zzip_init_io </td>
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<td width=50%> the recommended way to do things </td></tr>
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<tr><td width=50%> zzip_get_default_io </td>
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<td width=50%> used internally whenever you supply a null
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for the io-argument of a _ext_io()-call </td></tr>
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<tr><td width=50%> zzip_get_default_ext </td>
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<td width=50%> used internally but not exported </td></tr>
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</table></td></tr></table>
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And last some stdio-like replacements were build but these
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happen to be actually just small wrappers around the other
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posix-like magic-calls. It just offers some convenience
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since wrappers like "SDL_rwops" tend to use a stringised
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open-mode - and I took the occasion to fold the zzip-bits
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for the _ext_io-calls right in there recognized via
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special extensions to the openmode-string of zzip_fopen().
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<table cellpadding=10 width=100%><tr><td><table border=1 width=100%>
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<tr><td width=50%> zzip_fopen </td>
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<td width=50%> convert stringmode and call zzip_open_ext_io </td></tr>
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<tr><td width=50%> zzip_fread </td>
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<td width=50%> slower way to say zzip_read </td></tr>
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<tr><td width=50%> zzip_fclose </td>
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<td width=50%> a synonym of zzip_close </td></tr>
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</table></td></tr></table>
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For some reason, people did need the full set of function-calls()
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to be working on zzip-wrappers too, so here they are - if the
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ZZIP_FILE instance did wrap a real file, then the real posix-call
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will be used, otherwise it is simulated on the compressed stream
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with a zip-contained file - especially <code>seek()</code> can be
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if the new point is later then just read out more bytes till we
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hit that position but if it is an earlier point then rewind to the
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beginning of the compressed data and start reading/decompression
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until the position is met.
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<table cellpadding=10 width=100%><tr><td><table border=1 width=100%>
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<tr><td width=50%> zzip_rewind </td>
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<td width=50%> magic for rewind() </td></tr>
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<tr><td width=50%> zzip_tell </td>
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<td width=50%> magic for tell() </td></tr>
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<tr><td width=50%> zzip_seek </td>
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<td width=50%> magic for seek() </td></tr>
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</table></td></tr></table>
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And last not least, there are few informative functions to
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use function-calls to read parts of the opaque structures
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of zzip-objects and their zzip-factory.
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<table cellpadding=10 width=100%><tr><td><table border=1 width=100%>
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<tr><td width=50%> zzip_dir_stat </td>
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<td width=50%> a stat()-like thing on a file within a ZZIP_DIR </td></tr>
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<tr><td width=50%> zzip_dir_real </td>
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<td width=50%> check if ZZIP_DIR wraps a stat'able posix-dirent</td></tr>
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<tr><td width=50%> zzip_file_real </td>
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<td width=50%> check if ZZIP_FILE wraps a stat'able posix-file </td></tr>
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<tr><td width=50%> zzip_realdir </td>
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<td width=50%> if zzip_dir_real then return the posix-dirent </td></tr>
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<tr><td width=50%> zzip_realfd </td>
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<td width=50%> if zzip_file_real then return the posix-file </td></tr>
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<tr><td width=50%> zzip_dirhandle </td>
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<td width=50%> the attached ZZIP_DIR of compressed ZZIP_FILE </td></tr>
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<tr><td width=50%> zzip_dirfd </td>
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<td width=50%> the attached posix-file of ZZIP_DIR zip-file </td></tr>
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<tr><td width=50%> zzip_set_error </td>
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<td width=50%> set the last ZZIP_DIR error-code </td></tr>
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<tr><td width=50%> zzip_error </td>
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<td width=50%> get the last ZZIP_DIR error-code </td></tr>
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<tr><td width=50%> zzip_strerror </td>
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<td width=50%> convert a zzip_error into a readable string </td></tr>
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<tr><td width=50%> zzip_strerror_of </td>
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<td width=50%> combine both above zzip_strerror of zzip_error </td></tr>
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<tr><td width=50%> zzip_errno </td>
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<td width=50%> helper to wrap a zzip-error to a posix-errno </td></tr>
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<tr><td width=50%> zzip_compr_str </td>
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<td width=50%> helper to wrap a compr-number to a readable string
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<tr><td width=50%> zzip_dir_free </td>
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<td width=50%> internally called by zzip_dir_close if the ref-count
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of the ZZIP_DIR has gone zero</td></tr>
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<tr><td width=50%> zzip_freopen </td>
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<td width=50%> to reuse the ZZIP_DIR from another ZZIP_FILE so it does
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not need to be parsed again </td></tr>
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<tr><td width=50%> zzip_open_shared_io </td>
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<td width=50%> the ext/io cousin but it does not close the old ZZIP_FILE
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and instead just shares the ZZIP_DIR if possible</td></tr>
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</table></td></tr></table>