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90 lines
3.0 KiB
Plaintext
90 lines
3.0 KiB
Plaintext
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The "EEL Compressed Source" file format
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EEL Compressed Source files are EEL source files stripped of
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all comments and formatting information. They are tokenized
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using an external dictionary, which contains all keywords of
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EEL and extensions, and any project names. Immediate values
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are encoded using an extended "variable length number" BCD
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format.
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* EEL Compressed Source files should have the extension
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".eec" instead of the normal ".eel", for reliable
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identification, and to avoid accidentally overwriting
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source files with compressed source files. (That would
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be nasty, as the compression is destructive WRT comments,
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symbol names and code formatting...)
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* The files are based on 4 bit words. Wider words (8 or 16
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bits) are *not* aligned to 8 or 16 bits, but start
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directly at the current 4 bit word position.
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* There are two modes: XASCII and XBCD. Decoding of a file
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starts in the XASCII mode. XASCII codes are 8 bits, and
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XBCD codes are 4 bits.
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* The file starts with an 8 bit version code for the EEL
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dictionary to use. Then follows a list of 4 byte EEL
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extension IDs, terminated by a 0 byte. The EEL extension
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IDs are of the form "XXXv", where "XXX" is an acronym
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identifying the extension, and "v" is the version of the
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extension dictionary to use.
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Any extension ID that doesn't math any known EEL
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extension is assumed to be a Local Dictionary name.
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".eed" will be appended to the full 4 byte string (no
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version code), and then EEL will try to find a file by
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that name and load it as a Local Dictionary.
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* A Local Dictionary file consists of a 32 bit little
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endian integer that holds the number of tokens needed
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by the dictionary, *optionally* followed by a list of
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null terminated ASCII strings, holding the human
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readable names of all tokens. (The token name list is
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useful when mixing compressed source with ASCII source
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during development.)
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* Token values are allocated from 0 and up as
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dictionaries are loaded. This is why there are
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extension version numbers in the dictionary lists -
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and it should also make it obvious that EEL extensions
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must only *add* to their dictionaries if compatibility
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with old compressed sources is to be maintained.
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* XASCII code:
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0-14 XBCD code + enter XBCD mode
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15 Local token dictionary follows
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16 8 bit character follows
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17 Null terminated 8 bit quoted string
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18 Quoted 8 bit Pascal string follows
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19 Quoted 8 bit Pascal string continued
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20 <unused>
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21 <unused>
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22 <unused>
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23 <unused>
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24 <unused>
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25 <unused>
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26 <unused>
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27 <unused>
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28 <unused>
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29 <unused>
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30 <unused>
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31 <unused>
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32-127 Standard 7 bit ASCII (copied as is)
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128-191 Short Tokens
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192-254 Extended Tokens (8 extra bits follow)
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255 Wide Tokens (16 extra bits follow)
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* XBCD code:
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0-9 Decimal numbers 0-9
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10 Decimal point (.)
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11 Unary minus (-)
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12 Argument separator/white space
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13 Statement terminator (;)
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14 Single XASCII character follows
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15 Switch to XASCII mode
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