File: //lib/python3.9/site-packages/elftools/construct/__pycache__/core.cpython-39.pyc
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The mother of all constructs.
This object is generally not directly instantiated, and it does not
directly implement parsing and building, so it is largely only of interest
to subclass implementors.
The external user API:
* parse()
* parse_stream()
* build()
* build_stream()
* sizeof()
Subclass authors should not override the external methods. Instead,
another API is available:
* _parse()
* _build()
* _sizeof()
There is also a flag API:
* _set_flag()
* _clear_flag()
* _inherit_flags()
* _is_flag()
And stateful copying:
* __getstate__()
* __setstate__()
Attributes and Inheritance
==========================
All constructs have a name and flags. The name is used for naming struct
members and context dictionaries. Note that the name can either be a
string, or None if the name is not needed. A single underscore ("_") is a
reserved name, and so are names starting with a less-than character ("<").
The name should be descriptive, short, and valid as a Python identifier,
although these rules are not enforced.
The flags specify additional behavioral information about this construct.
Flags are used by enclosing constructs to determine a proper course of
action. Flags are inherited by default, from inner subconstructs to outer
constructs. The enclosing construct may set new flags or clear existing
ones, as necessary.
For example, if FLAG_COPY_CONTEXT is set, repeaters will pass a copy of
the context for each iteration, which is necessary for OnDemand parsing.
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Set the given flag or flags.
:param int flag: flag to set; may be OR'd combination of flags
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Clear the given flag or flags.
:param int flag: flag to clear; may be OR'd combination of flags
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Pull flags from subconstructs.
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Check whether a given flag is set.
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Obtain a dictionary representing this construct's state.
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Set this construct's state to a given state.
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Parse an in-memory buffer.
Strings, buffers, memoryviews, and other complete buffers can be
parsed with this method.
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Parse a stream.
Files, pipes, sockets, and other streaming sources of data are handled
by this method.
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Override me in your subclass.
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Build an object in memory.
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Build an object directly into a stream.
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t � �dS rM rO �r' rV rL rR r r r rX � s zConstruct._buildNc
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d}~0 0 dS )a�
Calculate the size of this object, optionally using a context.
Some constructs have no fixed size and can only know their size for a
given hunk of data; these constructs will raise an error if they are
not passed a context.
:param ``Container`` context: contextual data
:returns: int of the length of this construct
:raises SizeofError: the size could not be determined
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� Zd S ) � Subconstructz�
Abstract subconstruct (wraps an inner construct, inheriting its
name and flags).
Parameters:
* subcon - the construct to wrap
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S ) �Adapterz�
Abstract adapter: calls _decode for parsing and _encode for building.
Parameters:
* subcon - the construct to wrap
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A fixed-size byte field.
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A field that uses ``struct`` to pack and unpack data.
See ``struct`` documentation for instructions on crafting format strings.
:param str name: name of the field
:param str endianness: format endianness string; one of "<", ">", or "="
:param str format: a single format character
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� Zd S ) � MetaFielda
A variable-length field. The length is obtained at runtime from a
function.
:param str name: name of the field
:param callable lengthfunc: callable that takes a context and returns
length as an int
>>> foo = Struct("foo",
... Byte("length"),
... MetaField("data", lambda ctx: ctx["length"])
... )
>>> foo.parse("\x03ABC")
Container(data = 'ABC', length = 3)
>>> foo.parse("\x04ABCD")
Container(data = 'ABCD', length = 4)
�
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� Zd S ) � MetaArraya�
An array (repeater) of a meta-count. The array will iterate exactly
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See also Array, Range and RepeatUntil.
Parameters:
* countfunc - a function that takes the context as a parameter and returns
the number of elements of the array (count)
* subcon - the subcon to repeat `countfunc()` times
Example:
MetaArray(lambda ctx: 5, UBInt8("foo"))
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�Rangea�
A range-array. The subcon will iterate between `mincount` to `maxcount`
times. If less than `mincount` elements are found, raises RangeError.
See also GreedyRange and OptionalGreedyRange.
The general-case repeater. Repeats the given unit for at least mincount
times, and up to maxcount times. If an exception occurs (EOF, validation
error), the repeater exits. If less than mincount units have been
successfully parsed, a RangeError is raised.
.. note::
This object requires a seekable stream for parsing.
:param int mincount: the minimal count
:param int maxcount: the maximal count
:param Construct subcon: the subcon to repeat
>>> c = Range(3, 7, UBInt8("foo"))
>>> c.parse("\x01\x02")
Traceback (most recent call last):
...
construct.core.RangeError: expected 3..7, found 2
>>> c.parse("\x01\x02\x03")
[1, 2, 3]
>>> c.parse("\x01\x02\x03\x04\x05\x06")
[1, 2, 3, 4, 5, 6]
>>> c.parse("\x01\x02\x03\x04\x05\x06\x07")
[1, 2, 3, 4, 5, 6, 7]
>>> c.parse("\x01\x02\x03\x04\x05\x06\x07\x08\x09")
[1, 2, 3, 4, 5, 6, 7]
>>> c.build([1,2])
Traceback (most recent call last):
...
construct.core.RangeError: expected 3..7, found 2
>>> c.build([1,2,3,4])
'\x01\x02\x03\x04'
>>> c.build([1,2,3,4,5,6,7,8])
Traceback (most recent call last):
...
construct.core.RangeError: expected 3..7, found 8
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� Zd S ) � RepeatUntila�
An array that repeats until the predicate indicates it to stop. Note that
the last element (which caused the repeat to exit) is included in the
return value.
Parameters:
* predicate - a predicate function that takes (obj, context) and returns
True if the stop-condition is met, or False to continue.
* subcon - the subcon to repeat.
Example:
# will read chars until b (inclusive)
RepeatUntil(lambda obj, ctx: obj == b" ",
Field("chars", 1)
)
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r a�
A sequence of named constructs, similar to structs in C. The elements are
parsed and built in the order they are defined.
See also Embedded.
Parameters:
* name - the name of the structure
* subcons - a sequence of subconstructs that make up this structure.
* nested - a keyword-only argument that indicates whether this struct
creates a nested context. The default is True. This parameter is
considered "advanced usage", and may be removed in the future.
Example:
Struct("foo",
UBInt8("first_element"),
UBInt16("second_element"),
Padding(2),
UBInt8("third_element"),
)
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A sequence of unnamed constructs. The elements are parsed and built in the
order they are defined.
See also Embedded.
Parameters:
* name - the name of the structure
* subcons - a sequence of subconstructs that make up this structure.
* nested - a keyword-only argument that indicates whether this struct
creates a nested context. The default is True. This parameter is
considered "advanced usage", and may be removed in the future.
Example:
Sequence("foo",
UBInt8("first_element"),
UBInt16("second_element"),
Padding(2),
UBInt8("third_element"),
)
c C s� d|v r|d }|d= nt � }| jr.t|d�}| jD ]P}|j| j@ rZ||d< |�||� q4|�||�}|jd ur4|�|� |||j< q4|S r� ) r r� r r2 r rc rK r r� r� r r r rK � s
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d � Zd S )
�Uniona�
a set of overlapping fields (like unions in C). when parsing,
all fields read the same data; when building, only the first subcon
(called "master") is used.
Parameters:
* name - the name of the union
* master - the master subcon, i.e., the subcon used for building and
calculating the total size
* subcons - additional subcons
Example:
Union("what_are_four_bytes",
UBInt32("one_dword"),
Struct("two_words", UBInt16("first"), UBInt16("second")),
Struct("four_bytes",
UBInt8("a"),
UBInt8("b"),
UBInt8("c"),
UBInt8("d")
),
)
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dS )�Switchah
A conditional branch. Switch will choose the case to follow based on
the return value of keyfunc. If no case is matched, and no default value
is given, SwitchError will be raised.
See also Pass.
Parameters:
* name - the name of the construct
* keyfunc - a function that takes the context and returns a key, which
will ne used to choose the relevant case.
* cases - a dictionary mapping keys to constructs. the keys can be any
values that may be returned by keyfunc.
* default - a default value to use when the key is not found in the cases.
if not supplied, an exception will be raised when the key is not found.
You can use the builtin construct Pass for 'do-nothing'.
* include_key - whether or not to include the key in the return value
of parsing. defualt is False.
Example:
Struct("foo",
UBInt8("type"),
Switch("value", lambda ctx: ctx.type, {
1 : UBInt8("spam"),
2 : UBInt16("spam"),
3 : UBInt32("spam"),
4 : UBInt64("spam"),
}
),
)
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�SelectaL
Selects the first matching subconstruct. It will literally try each of
the subconstructs, until one matches.
Notes:
* requires a seekable stream.
Parameters:
* name - the name of the construct
* subcons - the subcons to try (order-sensitive)
* include_name - a keyword only argument, indicating whether to include
the name of the selected subcon in the return value of parsing. default
is false.
Example:
Select("foo",
UBInt64("large"),
UBInt32("medium"),
UBInt16("small"),
UBInt8("tiny"),
)
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zSelect.__init__c C s| | j D ]h}|�� }|�� }z|�||�}W n tyF |�|� Y q0 |�|� | jrf|j|f S | S qt d��d S �Nzno subconstruct matched)
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� Zd S ) �Pointeraj
Changes the stream position to a given offset, where the construction
should take place, and restores the stream position when finished.
See also Anchor, OnDemand and OnDemandPointer.
Notes:
* requires a seekable stream.
Parameters:
* offsetfunc: a function that takes the context and returns an absolute
stream position, where the construction would take place
* subcon - the subcon to use at `offsetfunc()`
Example:
Struct("foo",
UBInt32("spam_pointer"),
Pointer(lambda ctx: ctx.spam_pointer,
Array(5, UBInt8("spam"))
)
)
�
offsetfuncc C s t �| |� || _d S rf )rd r) r� )r' r� re r r r r) � s zPointer.__init__c C s8 | � |�}|�� }|�|� | j�||�}|�|� |S rf )r� r� r� re rK )r' rL rR �newpos�origposrV r r r rK � s
zPointer._parsec C s: | � |�}|�� }|�|� | j�|||� |�|� d S rf )r� r� r� re rX )r' rV rL rR r� r� r r r rX � s
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dd�Zdd� Zdd � Zd
d � Zd S )r� a�
Peeks at the stream: parses without changing the stream position.
See also Union. If the end of the stream is reached when peeking,
returns None.
Notes:
* requires a seekable stream.
Parameters:
* subcon - the subcon to peek at
* perform_build - whether or not to perform building. by default this
parameter is set to False, meaning building is a no-op.
Example:
Peek(UBInt8("foo"))
r� Fc C s t �| |� || _d S rf )rd r) r� )r' re r� r r r r) � s z
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r� c @ s2 e Zd ZdZddgZd dd�Zdd� Zd d
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�OnDemanda�
Allows for on-demand (lazy) parsing. When parsing, it will return a
LazyContainer that represents a pointer to the data, but does not actually
parses it from stream until it's "demanded".
By accessing the 'value' property of LazyContainers, you will demand the
data from the stream. The data will be parsed and cached for later use.
You can use the 'has_value' property to know whether the data has already
been demanded.
See also OnDemandPointer.
Notes:
* requires a seekable stream.
Parameters:
* subcon -
* advance_stream - whether or not to advance the stream position. by
default this is True, but if subcon is a pointer, this should be False.
* force_build - whether or not to force build. If set to False, and the
LazyContainer has not been demaned, building is a no-op.
Example:
OnDemand(Array(10000, UBInt8("foo"))
�advance_stream� force_buildTc C s t �| |� || _|| _d S rf )rd r) r� r� )r' re r� r� r r r r) � s zOnDemand.__init__c C s2 t | j||�� |�}| jr.|�| j�|�d� |S �Nr )r re r� r� r� rZ )r' rL rR rV r r r rK � s zOnDemand._parsec C sZ t |t�s | j�|||� n:| js(|jr<| j�|j||� n| jrV|�| j� |�d� d S r� )
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� Zd S ) �Buffereda
Creates an in-memory buffered stream, which can undergo encoding and
decoding prior to being passed on to the subconstruct.
See also Bitwise.
Note:
* Do not use pointers inside Buffered
Parameters:
* subcon - the subcon which will operate on the buffer
* encoder - a function that takes a string and returns an encoded
string (used after building)
* decoder - a function that takes a string and returns a decoded
string (used before parsing)
* resizer - a function that takes the size of the subcon and "adjusts"
or "resizes" it according to the encoding/decoding process.
Example:
Buffered(BitField("foo", 16),
encoder = decode_bin,
decoder = encode_bin,
resizer = lambda size: size / 8,
)
)�encoder�decoder�resizerc C s" t �| |� || _|| _|| _d S rf )rd r) r� r� r� )r' re r� r� r� r r r r) & s zBuffered.__init__c C s, t || �|��}t| �|��}| j�||�S rf )rr rZ r r� re rK )r' rL rR rI r� r r r rK + s zBuffered._parsec C sT | � |�}t� }| j�|||� | �|�� �}t|�|ks>J �t|| � |�|� d S rf )rZ r re rX r� rT ro rt )r' rV rL rR r{ r� rI r r r rX / s
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� Zd S ) �Restreama"
Wraps the stream with a read-wrapper (for parsing) or a
write-wrapper (for building). The stream wrapper can buffer the data
internally, reading it from- or writing it to the underlying stream
as needed. For example, BitStreamReader reads whole bytes from the
underlying stream, but returns them as individual bits.
See also Bitwise.
When the parsing or building is done, the stream's close method
will be invoked. It can perform any finalization needed for the stream
wrapper, but it must not close the underlying stream.
Note:
* Do not use pointers inside Restream
Parameters:
* subcon - the subcon
* stream_reader - the read-wrapper
* stream_writer - the write wrapper
* resizer - a function that takes the size of the subcon and "adjusts"
or "resizes" it according to the encoding/decoding process.
Example:
Restream(BitField("foo", 16),
stream_reader = BitStreamReader,
stream_writer = BitStreamWriter,
resizer = lambda size: size / 8,
)
)�
stream_reader�
stream_writerr� c C s" t �| |� || _|| _|| _d S rf )rd r) r� r� r� )r' re r� r� r� r r r r) X s zRestream.__init__c C s$ | � |�}| j�||�}|�� |S rf )r� re rK �close)r' rL rR r� rV r r r rK ] s
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Reconfigures a subconstruct. Reconfig can be used to change the name and
set and clear flags of the inner subcon.
Parameters:
* name - the new name
* subcon - the subcon to reconfigure
* setflags - the flags to set (default is 0)
* clearflags - the flags to clear (default is 0)
Example:
Reconfig("foo", UBInt8("bar"))
r c C s. t �| ||j� || _| �|� | �|� d S rf )r r) r re r0 r1 )r' r re ZsetflagsZ
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zReconfig.__init__N)r r )r r
r r` r r) r r r r r� m s
r� c @ s, e Zd ZdZg Zdd� Zdd� Zdd� ZdS ) �AnchoraM
Returns the "anchor" (stream position) at the point where it's inserted.
Useful for adjusting relative offsets to absolute positions, or to measure
sizes of constructs.
absolute pointer = anchor + relative offset
size = anchor_after - anchor_before
See also Pointer.
Notes:
* requires a seekable stream.
Parameters:
* name - the name of the anchor
Example:
Struct("foo",
Anchor("base"),
UBInt8("relative_offset"),
Pointer(lambda ctx: ctx.relative_offset + ctx.base,
UBInt8("data")
)
)
c C s |� � S rf )r� rQ r r r rK � s z
Anchor._parsec C s |� � || j< d S rf )r� r rY r r r rX � s z
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r r` r rK rX rZ r r r r r� � s
r� c @ s6 e Zd ZdZdgZdd� Zdd� Zdd� Zd d
� Zd S ) �Valuea8
A computed value.
Parameters:
* name - the name of the value
* func - a function that takes the context and return the computed value
Example:
Struct("foo",
UBInt8("width"),
UBInt8("height"),
Value("total_pixels", lambda ctx: ctx.width * ctx.height),
)
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Value._sizeofNrg r r r r r� � s r� c @ s8 e Zd ZdZddgZdd� Zdd� Zdd � Zd
d � Zd S )
� LazyBounda
Lazily bound construct, useful for constructs that need to make cyclic
references (linked-lists, expression trees, etc.).
Parameters:
Example:
foo = Struct("foo",
UBInt8("bar"),
LazyBound("next", lambda: foo),
)
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S ) �Passa
A do-nothing construct, useful as the default case for Switch, or
to indicate Enums.
See also Switch and Enum.
Notes:
* this construct is a singleton. do not try to instatiate it, as it
will not work...
Example:
Pass
c C s d S rf r rQ r r r rK s z Pass._parsec C s |d u s J �d S rf r rY r r r rX s z Pass._buildc C s dS r r r_ r r r rZ s z Pass._sizeofc C s | j jS rf )r* r r+ r r r �
__reduce__ s zPass.__reduce__N) r r
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Terminatorao
Asserts the end of the stream has been reached at the point it's placed.
You can use this to ensure no more unparsed data follows.
Notes:
* this construct is only meaningful for parsing. for building, it's
a no-op.
* this construct is a singleton. do not try to instatiate it, as it
will not work...
Example:
Terminator
c C s |� d�rtd��d S )Nr zexpected end of stream)rn r rQ r r r rK ' s
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r� )0�structr rz Z
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