Hi,
I'm trying to parse a "binary" file with the help of gloss. My problem
is, the data is in a format that gloss seeminglydoesn't deal with at all.
The file start with a plaintext header, followed by some binary data,
which may be compressed in various formats. What I'm trying to
do is parse the header, and then store the binary blobs away to be
decompressed later.
A typical header looks like this:
SPKCycrow;4.20;1;727\r\n
<binary prefix>[<binary data>...]
That's in order: FileType magic string, FileType version, enum for
compression format, length of compressed data, linebreak, :int32-be
length of decompressed data and then the data (in my case zlib).
Here's how far I got:
-----------------------------------------------------------------------
(defcodec compression (enum :byte {:none \0, :zlib \1, :7zip \2,
:lzma \3, :best \4}))
(defcodec file-header
(ordered-map :filetype (string :utf-8 :delimiters [";"])
:spkversion (string :utf-8 :delimiters [";"])
:compression compression
:junk :byte
))
(defcodec blocksize (string-integer :utf-8 :delimiters ["\n"]))
(defcodec value
(ordered-map :size blocksize
:decompsize :int32-be
:data (finite-frame ??? (repeated :byte :prefix
:none))))
(defcodec payload (repeated :byte :prefix :none))
(defcodec spkfile [file-header value payload])
-----------------------------------------------------------------------
My 2 problems:
- note the :junk in file-header, this I had to do since enum only accepts
primitives. (This also means enum switches on the ASCII-value of the
number instead of the actual number.) Is there a better way to coerce
"1;", "2;", etc. into an enum?
- the ??? in the finite-frame of value, what do I put there? how do I get
blocksize into the size definition of the frame? Gloss seems to assume
that any such definitions *directly* precede the following data.
Any pointers are greatly appreciated.
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