ghidra::PackedDecode Class Reference

A byte-based decoder designed to marshal info to the decompiler efficiently. More...

#include <marshal.hh>

Inheritance diagram for ghidra::PackedDecode:

Classes
class	ByteChunk
	A bounded array of bytes. More...
class	Position
	An iterator into input stream. More...

Public Member Functions
	PackedDecode (const AddrSpaceManager *spcManager)
	Constructor.
virtual void	ingestStream (istream &s)
	Prepare to decode a given stream. More...
virtual uint4	peekElement (void)
	Peek at the next child element of the current parent, without traversing in (opening) it. More...
virtual uint4	openElement (void)
	Open (traverse into) the next child element of the current parent. More...
virtual uint4	openElement (const ElementId &elemId)
	Open (traverse into) the next child element, which must be of a specific type. More...
virtual void	closeElement (uint4 id)
	Close the current element. More...
virtual void	closeElementSkipping (uint4 id)
	Close the current element, skipping any child elements that have not yet been parsed. More...
virtual void	rewindAttributes (void)
	Reset attribute traversal for the current element. More...
virtual uint4	getNextAttributeId (void)
	Get the next attribute id for the current element. More...
virtual uint4	getIndexedAttributeId (const AttributeId &attribId)
	Get the id for the (current) attribute, assuming it is indexed. More...
virtual bool	readBool (void)
	Parse the current attribute as a boolean value. More...
virtual bool	readBool (const AttributeId &attribId)
	Find and parse a specific attribute in the current element as a boolean value. More...
virtual intb	readSignedInteger (void)
	Parse the current attribute as a signed integer value. More...
virtual intb	readSignedInteger (const AttributeId &attribId)
	Find and parse a specific attribute in the current element as a signed integer. More...
virtual intb	readSignedIntegerExpectString (const string &expect, intb expectval)
	Parse the current attribute as either a signed integer value or a string. More...
virtual intb	readSignedIntegerExpectString (const AttributeId &attribId, const string &expect, intb expectval)
	Find and parse a specific attribute in the current element as either a signed integer or a string. More...
virtual uintb	readUnsignedInteger (void)
	Parse the current attribute as an unsigned integer value. More...
virtual uintb	readUnsignedInteger (const AttributeId &attribId)
	Find and parse a specific attribute in the current element as an unsigned integer. More...
virtual string	readString (void)
	Parse the current attribute as a string. More...
virtual string	readString (const AttributeId &attribId)
	Find the specific attribute in the current element and return it as a string. More...
virtual AddrSpace *	readSpace (void)
	Parse the current attribute as an address space. More...
virtual AddrSpace *	readSpace (const AttributeId &attribId)
	Find the specific attribute in the current element and return it as an address space. More...
Public Member Functions inherited from ghidra::Decoder
	Decoder (const AddrSpaceManager *spc)
	Base constructor.
const AddrSpaceManager *	getAddrSpaceManager (void) const
	Get the manager used for address space decoding.
virtual	~Decoder (void)
	Destructor.
void	skipElement (void)
	Skip parsing of the next element. More...

Static Public Attributes
static const int4	BUFFER_SIZE = 1024
	The size, in bytes, of a single cached chunk of the input stream.

Private Member Functions
uint1	getByte (Position &pos)
	Get the byte at the current position, do not advance.
uint1	getBytePlus1 (Position &pos)
	Get the byte following the current byte, do not advance position. More...
uint1	getNextByte (Position &pos)
	Get the byte at the current position and advance to the next byte. More...
void	advancePosition (Position &pos, int4 skip)
	Advance the position by the given number of bytes. More...
uint8	readInteger (int4 len)
	Read an integer from the current position given its length in bytes. More...
uint4	readLengthCode (uint1 typeByte)
	Extract length code from type byte.
void	findMatchingAttribute (const AttributeId &attribId)
	Find attribute matching the given id in open element. More...
void	skipAttribute (void)
	Skip over the attribute at the current position. More...
void	skipAttributeRemaining (uint1 typeByte)
	Skip over remaining attribute data, after a mismatch. More...

Private Attributes
list< ByteChunk >	inStream
	Incoming raw data as a sequence of byte arrays.
Position	startPos
	Position at the start of the current open element.
Position	curPos
	Position of the next attribute as returned by getNextAttributeId.
Position	endPos
	Ending position after all attributes in current open element.
bool	attributeRead
	Has the last attribute returned by getNextAttributeId been read.

Additional Inherited Members
Protected Attributes inherited from ghidra::Decoder
const AddrSpaceManager *	spcManager
	Manager for decoding address space attributes.

Detailed Description

A byte-based decoder designed to marshal info to the decompiler efficiently.

The decoder expects an encoding as described in PackedFormat. When ingested, the stream bytes are held in a sequence of arrays (ByteChunk). During decoding, this object maintains a Position in the stream at the start and end of the current open element, and a Position of the next attribute to read to facilitate getNextAttributeId() and associated read*() methods.

Member Function Documentation

advancePosition()

void ghidra::PackedDecode::advancePosition ( Position &  pos, int4  skip  )

inlineprivate

Advance the position by the given number of bytes.

An exception is thrown of position is advanced past the end of the stream

Parameters

pos	is the position being advanced
skip	is the number of bytes to advance

References ghidra::PackedDecode::Position::current, ghidra::PackedDecode::Position::end, and ghidra::PackedDecode::Position::seqIter.

closeElement()

void ghidra::PackedDecode::closeElement ( uint4  id )

virtual

Close the current element.

The data for the current element is considered fully processed. If the element has additional children, an exception is thrown. The stream must indicate the end of the element in some way.

Parameters

id	is the id of the element to close (which must be the current element)

Implements ghidra::Decoder.

Referenced by ghidra::ContextGhidra::getTrackedSet().

closeElementSkipping()

void ghidra::PackedDecode::closeElementSkipping ( uint4  id )

virtual

Close the current element, skipping any child elements that have not yet been parsed.

This closes the given element, which must be current. If there are child elements that have not been parsed, this is not considered an error, and they are skipped over in the parse.

Parameters

id	is the id of the element to close (which must be the current element)

Implements ghidra::Decoder.

findMatchingAttribute()

void ghidra::PackedDecode::findMatchingAttribute ( const AttributeId &  attribId )

private

Find attribute matching the given id in open element.

The current position is reset to the start of the current open element. Attributes are scanned and skipped until the attribute matching the given id is found. The current position is set to the start of the matching attribute, in preparation for one of the read*() methods. If the id is not found an exception is thrown.

Parameters

attribId

is the attribute id to scan for.

getBytePlus1()

uint1 ghidra::PackedDecode::getBytePlus1 ( Position &  pos )

inlineprivate

Get the byte following the current byte, do not advance position.

An exception is thrown if the position currently points to the last byte in the stream

Parameters

pos	is the position in the stream to look ahead from

Returns

the next byte

References ghidra::PackedDecode::Position::current, ghidra::PackedDecode::Position::end, and ghidra::PackedDecode::Position::seqIter.

getIndexedAttributeId()

uint4 ghidra::PackedDecode::getIndexedAttributeId ( const AttributeId &  attribId )

virtual

Get the id for the (current) attribute, assuming it is indexed.

Assuming the previous call to getNextAttributeId() returned the id of ATTRIB_UNKNOWN, reinterpret the attribute as being an indexed form of the given attribute. If the attribute matches, return this indexed id, otherwise return ATTRIB_UNKNOWN.

Parameters

attribId

is the attribute being indexed

Returns

the indexed id or ATTRIB_UNKNOWN

Implements ghidra::Decoder.

getNextAttributeId()

uint4 ghidra::PackedDecode::getNextAttributeId ( void  )

virtual

Get the next attribute id for the current element.

Attributes are automatically set up for traversal using this method, when the element is opened. If all attributes have been traversed (or there are no attributes), 0 is returned.

Returns

the id of the next attribute or 0

Implements ghidra::Decoder.

getNextByte()

uint1 ghidra::PackedDecode::getNextByte ( Position &  pos )

inlineprivate

Get the byte at the current position and advance to the next byte.

An exception is thrown if there are no additional bytes in the stream

Parameters

pos	is the position of the byte

Returns

the byte at the current position

References ghidra::PackedDecode::Position::current, ghidra::PackedDecode::Position::end, and ghidra::PackedDecode::Position::seqIter.

ingestStream()

void ghidra::PackedDecode::ingestStream ( istream &  s )

virtual

Prepare to decode a given stream.

Called once before any decoding. Currently this is assumed to make an internal copy of the stream data, i.e. the input stream is cleared before any decoding takes place.

Parameters

s	is the given input stream to be decode

Returns

true if the stream was fully ingested

Implements ghidra::Decoder.

openElement() [1/2]

uint4 ghidra::PackedDecode::openElement ( void  )

virtual

Open (traverse into) the next child element of the current parent.

The child becomes the current parent. The list of attributes is initialized for use with getNextAttributeId.

Returns

the id of the child element

Implements ghidra::Decoder.

Referenced by ghidra::ContextGhidra::getTrackedSet(), and ghidra::GhidraTranslate::oneInstruction().

openElement() [2/2]

uint4 ghidra::PackedDecode::openElement ( const ElementId &  elemId )

virtual

Open (traverse into) the next child element, which must be of a specific type.

The child becomes the current parent, and its attributes are initialized for use with getNextAttributeId. The child must match the given element id or an exception is thrown.

Parameters

elemId

is the given element id to match

Returns

the id of the child element

Implements ghidra::Decoder.

peekElement()

uint4 ghidra::PackedDecode::peekElement ( void  )

virtual

Peek at the next child element of the current parent, without traversing in (opening) it.

The element id is returned, which can be compared to ElementId labels. If there are no remaining child elements to traverse, 0 is returned.

Returns

the element id or 0

Implements ghidra::Decoder.

Referenced by ghidra::GhidraTranslate::oneInstruction().

readBool() [1/2]

bool ghidra::PackedDecode::readBool ( void  )

virtual

Parse the current attribute as a boolean value.

The last attribute, as returned by getNextAttributeId, is treated as a boolean, and its value is returned.

Returns

the boolean value associated with the current attribute.

Implements ghidra::Decoder.

readBool() [2/2]

bool ghidra::PackedDecode::readBool ( const AttributeId &  attribId )

virtual

Find and parse a specific attribute in the current element as a boolean value.

The set of attributes for the current element is searched for a match to the given attribute id. This attribute is then parsed as a boolean and its value returned. If there is no attribute matching the id, an exception is thrown. Parsing via getNextAttributeId is reset.

Parameters

attribId

is the specific attribute id to match

Returns

the boolean value

Implements ghidra::Decoder.

readInteger()

uint8 ghidra::PackedDecode::readInteger ( int4  len )

private

Read an integer from the current position given its length in bytes.

The integer is encoded, 7-bits per byte, starting with the most significant 7-bits. The integer is decode from the current position, and the position is advanced.

Parameters

len	is the number of bytes to extract

readSignedInteger() [1/2]

intb ghidra::PackedDecode::readSignedInteger ( void  )

virtual

Parse the current attribute as a signed integer value.

The last attribute, as returned by getNextAttributeId, is treated as a signed integer, and its value is returned.

Returns

the signed integer value associated with the current attribute.

Implements ghidra::Decoder.

Referenced by ghidra::GhidraTranslate::oneInstruction().

readSignedInteger() [2/2]

intb ghidra::PackedDecode::readSignedInteger ( const AttributeId &  attribId )

virtual

Find and parse a specific attribute in the current element as a signed integer.

The set of attributes for the current element is searched for a match to the given attribute id. This attribute is then parsed as a signed integer and its value returned. If there is no attribute matching the id, an exception is thrown. Parsing via getNextAttributeId is reset.

Parameters

attribId

is the specific attribute id to match

Returns

the signed integer value

Implements ghidra::Decoder.

readSignedIntegerExpectString() [1/2]

intb ghidra::PackedDecode::readSignedIntegerExpectString ( const string &  expect, intb  expectval  )

virtual

Parse the current attribute as either a signed integer value or a string.

If the attribute is an integer, its value is returned. If the attribute is a string, it must match an expected string passed to the method, and a predetermined integer value associated with the string is returned. If the attribute neither matches the expected string nor is an integer, the return value is undefined.

Parameters

expect	is the string value to expect if the attribute is encoded as a string
expectval	is the integer value to return if the attribute matches the expected string

Returns

the encoded integer or the integer value associated with the expected string

Implements ghidra::Decoder.

readSignedIntegerExpectString() [2/2]

intb ghidra::PackedDecode::readSignedIntegerExpectString ( const AttributeId &  attribId, const string &  expect, intb  expectval  )

virtual

Find and parse a specific attribute in the current element as either a signed integer or a string.

If the attribute is an integer, its value is parsed and returned. If the attribute is encoded as a string, it must match an expected string passed to this method. In this case, a predetermined integer value is passed back, indicating a matching string was parsed. If the attribute neither matches the expected string nor is an integer, the return value is undefined. If there is no attribute matching the id, an exception is thrown.

Parameters

attribId	is the specific attribute id to match
expect	is the string to expect, if the attribute is not encoded as an integer
expectval	is the integer value to return if the attribute matches the expected string

Returns

the encoded integer or the integer value associated with the expected string

Implements ghidra::Decoder.

readSpace() [1/2]

AddrSpace * ghidra::PackedDecode::readSpace ( void  )

virtual

Parse the current attribute as an address space.

The last attribute, as returned by getNextAttributeId, is returned as an address space.

Returns

the address space associated with the current attribute.

Implements ghidra::Decoder.

readSpace() [2/2]

AddrSpace * ghidra::PackedDecode::readSpace ( const AttributeId &  attribId )

virtual

Find the specific attribute in the current element and return it as an address space.

Search attributes from the current element for a match to the given attribute id. Return this attribute as an address space. If there is no attribute matching the id, an exception is thrown. Parse via getNextAttributeId is reset.

Parameters

attribId

is the specific attribute id to match

Returns

the address space associated with the attribute

Implements ghidra::Decoder.

readString() [1/2]

string ghidra::PackedDecode::readString ( void  )

virtual

Parse the current attribute as a string.

The last attribute, as returned by getNextAttributeId, is returned as a string.

Returns

the string associated with the current attribute.

Implements ghidra::Decoder.

readString() [2/2]

string ghidra::PackedDecode::readString ( const AttributeId &  attribId )

virtual

Find the specific attribute in the current element and return it as a string.

The set of attributes for the current element is searched for a match to the given attribute id. This attribute is then returned as a string. If there is no attribute matching the id, and exception is thrown. Parse via getNextAttributeId is reset.

Parameters

attribId

is the specific attribute id to match

Returns

the string associated with the attribute

Implements ghidra::Decoder.

readUnsignedInteger() [1/2]

uintb ghidra::PackedDecode::readUnsignedInteger ( void  )

virtual

Parse the current attribute as an unsigned integer value.

The last attribute, as returned by getNextAttributeId, is treated as an unsigned integer, and its value is returned.

Returns

the unsigned integer value associated with the current attribute.

Implements ghidra::Decoder.

readUnsignedInteger() [2/2]

uintb ghidra::PackedDecode::readUnsignedInteger ( const AttributeId &  attribId )

virtual

Find and parse a specific attribute in the current element as an unsigned integer.

The set of attributes for the current element is searched for a match to the given attribute id. This attribute is then parsed as an unsigned integer and its value returned. If there is no attribute matching the id, an exception is thrown. Parsing via getNextAttributeId is reset.

Parameters

attribId

is the specific attribute id to match

Returns

the unsigned integer value

Implements ghidra::Decoder.

rewindAttributes()

void ghidra::PackedDecode::rewindAttributes ( void  )

virtual

Reset attribute traversal for the current element.

Attributes for a single element can be traversed more than once using the getNextAttributeId method.

Implements ghidra::Decoder.

skipAttribute()

void ghidra::PackedDecode::skipAttribute ( void  )

private

Skip over the attribute at the current position.

The attribute at the current position is scanned enough to determine its length, and the position is advanced to the following byte.

skipAttributeRemaining()

void ghidra::PackedDecode::skipAttributeRemaining ( uint1  typeByte )

private

Skip over remaining attribute data, after a mismatch.

This assumes the header and type byte have been read. Decode type and length info and finish skipping over the attribute so that the next call to getNextAttributeId() is on cut.

Parameters

typeByte

is the previously scanned type byte

---

The documentation for this class was generated from the following files:

• marshal.hh
• marshal.cc