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资源说明：A sketching app for file formats
Sketchpad 0.2b
==============
The Lemon Man (C) 2010
An useful tool when you just need to focus on reversing a file format
instead of writing a parser. You can quickly and easily write a sketch
file that describes the file structure and you'll get infos from the
file using the structure you just sketched.
Documentation
-------------
You can write comments in newlines by putting @ as first char.
Structure field descriptions are made in this way :
: :
Where it's one of the supported types for reading, listed
below.
byte - 8bit
hword - 16bit
word - 32bit
dword - 64bit
The field specifies the field endianness and can assume one
of the following values:
be - Big Endian
le - Little Endian
There's a special notation for the 'string' data type, it's the same as
above but instead of the endianness holds the string length. The string
length can be either a constant, a field name or one of the following
special flags:
z - Reads until a zero char is reached
uz - Same as above but for Unicode
Eg.
string : :
Same goes for the 'bytearr' data type, where the second field holds the
array size.
Eg.
bytearr : :
Remember that you may also use a structure field name instead of a
constant length.
A seeking function is implemented too and can be called as follows:
seekto : :
You can specify a fixed offset or a structure field name (that has been
already parsed). The whence field works as it does for any programming
language, 0 means the offset is absolute, 1 means that the offset is
relative to the current position and 2 means that the offset is relative
to the end of file.
As of 0.2 support to loops has been introduced. Declaring a loop is easy
as doing:
loop :
...
...
...
repeat
and every field included between the two loop markers will be executed
. The field that get parsed in the loop have the prefix '_loop_N'
appended (where N is the iteration number) for better recognizing 'em in
the resulting report. When inside a loop the parser replaces the tag
{loop}
in the field names with the current iteration number, this is meant for
accessing indexed fields read in a loop.
See foster.sketch for an useful example.
Nested loops aren't supported.
As of 0.2b the ability of extracting chunks of the file has been added.
The syntax is:
extract : :
The loop prefix is added to file name if the function is called inside a
loop.
See the included pbp.sketch for an example of a simple sketch file,
foster.sketch is a bit more complicated but shows the full potential of
the sketchpad.
Todo
----
* Proper Unicode char handling (?)
* EOF checks (?)
* Clean up some parts (?)
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