81 lines
1.8 KiB
Plaintext
81 lines
1.8 KiB
Plaintext
LaymansHex
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==========
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LaymansHex takes a (partial) file description and allows tinkering with
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the values in a binary file. It thus serves as a sort of layman's
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hex editor.
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File description format
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-----------------------
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In EBNF:
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```
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description =
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{ comment }
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endianness
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definition
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{ definition }
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.
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comment = '#' { LETTER | DIGIT } '\n'.
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endianness = ("little endian" | "big endian") '\n'.
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definition = [ IDENT ] ':' type '\n'.
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type = bytefield
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| "int8" | "int16" | "int32" | "int64"
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| "uint8" | "uint16" | "uint32" | "uint64"
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| "float32" | "float64"
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.
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bytefield = "byte[" size "]".
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size = INTEGER | ( IDENT [ "*" INTEGER ]).
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```
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The identifier of a definition line can be left empty to ignore that particular value.
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Portions of the binary file not covered by the file description are ignored. Byte field
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size can be variable - the specific value then needs to be set at program invocation (via -fvar).
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Usage
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-----
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To get values: `laymanshex FORMATFILE BINARY`
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To set values: `laymanshex -set "key1=value1,key2=value2" FORMATFILE BINARY`
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To set a variable 'offset' to 113 in the file description and get values: `laymanshex -fvar="offset=113" FORMATFILE BINARY`
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Examples of format descriptions can be found in the [laymanshex-files repo](/laymanshex-files/).
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Advanced
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--------
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The variable byte field size allows to script around laymanshex and use a sliding frame
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to obtain sequences. E.g. you can define a partial file format that only covers one
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element of the sequence at a certain offset:
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```
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little endian
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: byte[offset*32]
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value : int32
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```
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Script:
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```
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#/bin/bash
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for i in `seq 99`; do
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laymanshex -fvar="offset=$((i*4))" FORMATFILE BINARY
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done
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```
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If your sequence ends with a marker, add that marker to the file description and check
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its value after each invocation of laymanshex.
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