#include <memory_masking_gadget.hpp>

Inheritance diagram for libsnark::memory_masking_gadget< FieldT >:

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Collaboration diagram for libsnark::memory_masking_gadget< FieldT >:

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Public Member Functions
	memory_masking_gadget (tinyram_protoboard< FieldT > &pb, const doubleword_variable_gadget< FieldT > &dw_contents_prev, const dual_variable_gadget< FieldT > &subaddress, const pb_linear_combination< FieldT > &subcontents, const pb_linear_combination< FieldT > &access_is_word, const pb_linear_combination< FieldT > &access_is_byte, const doubleword_variable_gadget< FieldT > &dw_contents_next, const std::string &annotation_prefix="")

void	generate_r1cs_constraints ()

void	generate_r1cs_witness ()

Public Member Functions inherited from libsnark::tinyram_standard_gadget< FieldT >
	tinyram_standard_gadget (tinyram_protoboard< FieldT > &pb, const std::string &annotation_prefix="")

Public Member Functions inherited from libsnark::tinyram_gadget< FieldT >
	tinyram_gadget (tinyram_protoboard< FieldT > &pb, const std::string &annotation_prefix="")

Public Member Functions inherited from libsnark::gadget< FieldT >
	gadget (protoboard< FieldT > &pb, const std::string &annotation_prefix)

Public Attributes
doubleword_variable_gadget< FieldT >	dw_contents_prev

dual_variable_gadget< FieldT >	subaddress

pb_linear_combination< FieldT >	subcontents

pb_linear_combination< FieldT >	access_is_word

pb_linear_combination< FieldT >	access_is_byte

doubleword_variable_gadget< FieldT >	dw_contents_next

Additional Inherited Members
Protected Attributes inherited from libsnark::tinyram_gadget< FieldT >
tinyram_protoboard< FieldT > &	pb

Protected Attributes inherited from libsnark::gadget< FieldT >
protoboard< FieldT > &	pb

const std::string	annotation_prefix

Detailed Description

template<typename FieldT>
class libsnark::memory_masking_gadget< FieldT >

The memory masking gadget checks if a specified part of a double word is correctly modified. In TinyRAM CPU checker we use this to implement byte addressing and word addressing for the memory that consists of double words.

More precisely, memory masking gadgets takes the following arguments:

dw_contents_prev, dw_contents_next – the contents of the memory

double word before and after the access

access_is_word – a boolean indicating if access is word

access_is_byte – a boolean indicating if access is byte

subaddress – an integer specifying which byte (if access_is_byte=1) or word (if access_is_byte=1) this access is operating on

subcontents – contents of the byte, resp., word to be operated on

Memory masking gadget enforces that dw_contents_prev is equal to dw_contents_next everywhere, except subaddres-th byte (if access_is_byte = 1), or MSB(subaddress)-th word (if access_is_word = 1). The corresponding byte, resp., word in dw_contents_next is required to equal subcontents.

Note that indexing MSB(subaddress)-th word is the same as indexing the word specified by subaddress expressed in bytes and aligned to the word boundary by rounding the subaddress down.

Requirements: The caller is required to perform bounds checks on subcontents. The caller is also required to ensure that exactly one of access_is_word and access_is_byte is set to 1.

Definition at line 58 of file memory_masking_gadget.hpp.

Constructor & Destructor Documentation

◆ memory_masking_gadget()

template<typename FieldT >

libsnark::memory_masking_gadget< FieldT >::memory_masking_gadget	(	tinyram_protoboard< FieldT > &	pb,
		const doubleword_variable_gadget< FieldT > &	dw_contents_prev,
		const dual_variable_gadget< FieldT > &	subaddress,
		const pb_linear_combination< FieldT > &	subcontents,
		const pb_linear_combination< FieldT > &	access_is_word,
		const pb_linear_combination< FieldT > &	access_is_byte,
		const doubleword_variable_gadget< FieldT > &	dw_contents_next,
		const std::string &	annotation_prefix = `""`
	)