Taken from the file plugins.h in the Zoom distribution.
/*
* The Zoom archive format is:
*
* (char) Magic1
* (char) Magic2 - or - (char) Magic2B
* (char) Magic3
* (char) Magic4
*
* IF Magic2B was received THEN
* (long) logicalEof /* For multi-file archives * /
* END IF
*
* <EntryChain>
*
* The format of <EntryChain> is a linked list of
* EntryInfo, where "next" points to the next logical address
* on disk. "next" as 0 means no more entries.
*
* For a directory, the "creator" field points to the
* first file/folder entry inside the directory.
*
* For a file, IF the "what" field is ZOOM_PLUGIN,
* the EntryInfo is followed by a length byte and that
* many characters naming the compression engine.
* Right after that (or right after the EntryInfo in the
* case of uncompressed files or default compressed files)
* follows the data fork compressed, followed by the
* resource fork compressed.
*
* Note that there is no "end of compressed data" marker;
* your compressor engine will have to figure that out by
* itself. You could for instance do an ftell before
* compressing; writing a (long)0 and then write your
* compressed data, seek back and write the actual length.
*
* Note that new entries always are added last in the file,
* so you need not worry about overrunning anything else.
*/
/*
* The default compressor in Zoom is the same as used in
* "better" compression mode in ZOO 2.10. A Zoo extractor
* or convertor could parse the ZOO header format, and use
* the built-in engine for "lzh" compressed files.
*
* The simplest way to do this is to call SetEngine(-1) and
* call Encode / Decode. -1 is the default compressor, 0 is
* the null compressor (fork copy)
*
* Likewise, a UNIX zoom packer/unpacker could use the source
* for zoo 2.10 functions "lzh_encode" and "lzh_decode"
* (they're wrappers) for compression.
*/
/*
* This "EntryInfo" is presently also a file header.
* Some fields may be non-obvious. Don't use these.
* For instance, "comment" is currently unsupported,
* and should be left as 0
*/
#ifndef ZOOM_TYPES
typedef enum zoomWhatType {
ZOOM_NOTHING , ZOOM_FILE , ZOOM_UCFILE , ZOOM_DIR , ZOOM_PLUGIN
} ZoomWhatType ;
#define ZOOM_TYPES
#endif
/*
* Remember to fill in "hlen" correctly as well. When reading a header,
* Zoom checks with this field to see if it should skip some more data
* or seek back a little, so as to make future field additions at the
* end possible. You should NOT add your own fields to this structure.
*/
typedef struct EntryInfo {
/* "what" is a ZoomWhatType */
char what ; /* Negative if deleted */
unsigned char hlen ; /* Header length */
unsigned short boolFlags ; /* Boolean flags */
long next ; /* Next entry */
long complen ; /* Length of compressed data */
long compdata ; /* Data fork portion of compressed data - for dirs, number of entries */
long uclen ; /* Length of uncompressed entry */
long ucdata ; /* Data fork part of uncompressed */
long type ; /* File type */
long creator ; /* File creator - for dir, offset of file */
long mdate ; /* Modification date */
long comment ; /* Comment offset */
short flags ; /* Macintosh file flags */
short dataCrc ; /* Data fork crc */
short resCrc ; /* Resource fork crc */
unsigned char name [ 32 ] ; /* File/Dir name */
} EntryInfo ;
613fac05c0