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Max Horn
74 lines
3.7 KiB
HTML
74 lines
3.7 KiB
HTML
<HTML>
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<HEAD>
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<TITLE>Size Formats</TITLE>
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<META NAME="resource-type" CONTENT="document">
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<FONT SIZE="+2" FACE="Arial">
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<B>Size Formats</B>
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</FONT><P>
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<FONT FACE="Arial" SIZE="-1">
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If you have read some of the specifications of SCUMM blocks, you'll notice
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that they don't all include their size in the same way. In order to find
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the next block when analyzing (and in order to dump to files and process
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blocks correctly) SCUMM Revisited has to know the size of the current one.
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Thus, it needs to know the size format of each block. Just for those
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interested in internal stuff, here is a list of the different size formats
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used by SCUMM - and SCUMM Revisited:<P>
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<B>Standard:</B> The format I have chosen to call "Standard" is
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the one most commonly used in blocks for newer SCUMM games. All of these
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blocks start with four characters containing the block type (e.g. "LECF")
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followed by four bytes containing the size in little endian format
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(e.g. 00 01 32 2F - a size of 78383 bytes). These eight bytes are included
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in the size.<P>
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<B>Name and Size not Included:</B> This format is almost the same as the
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Standard format. The only difference is that here, the eight bytes containing
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the block type and size are not included in the size. So to get the correct
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size of the block we add 8.<P>
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<B>Name and Size not Included - Inconsistent:</B> This format is the same
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as the one described right above, except that sometimes this block has one
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more byte than the size says.<P>
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<B>Undefined - Based on Parent or Filesize:</B> Some blocks do not contain
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any useable size information at all. An example is the Creative Voice File
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blocks. Creative Voice Files (.voc) do not contain any information on their
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own size, which is probably why LEC placed those files within a wrapper
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block named VTLK for Full Throttle . Luckily, there is usually always a
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way to find the size anyway. Some blocks are known to be the root blocks of
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a file, and thus are just set to the size of the resource file. Others are
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always the last blocks within a parent block, and thus the size can be
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derived from the parent block size, by subtracting the size of all other
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sub-blocks (i.e. the offset of the current block, relative to the parent
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block offset) from the size of the parent.<P>
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<B>Entry Based:</B> Some blocks, such as MCMP and COMP, contain their sizes
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not in bytes, but in entries. So, to get the byte size, we multiply the size of
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each entry with the number of entries and add the 8 starting bytes mentioned
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above + the bytes containing the number of entries.<P>
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<B>Directory Table:</B> In bundle files, the block types/names and sizes of
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the contained files are listed in a directory at the start of the bundle file.
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This size format is used for such blocks.<P>
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<B>Old SCUMM:</B> For the early games Indiana Jones and the Last Crusade and
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Secret of Monkey Island, the entire file format was quite different: Each
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block started with the four bytes containing the size of the block in <I>big</I>
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endian followed by <I>two</I> characters for the block type identifier.<P>
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<B>VOC:</B> The Creative Voice Files (.voc) do not contain any info on
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size, which is the reason why MONSTER.SOU files take so long to analyze.
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In order to find the size, SCUMM Revisited parses the file's data in
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order to find the end of the file.<P>
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<B>Unknown:</B> Unknown is used for blocks that SCUMM Revisited does not
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know of. Other than displaying "Unknown" in the info panel, I
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decided to let this format be the same as the Undefined format, which is
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the safest and will allow more files to be opened that SCUMM Revisited was
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not made for ;)<P>
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</FONT>
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</BODY>
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</HTML>
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