DPDK::ConvertLookahead Struct Reference

Inheritance diagram for DPDK::ConvertLookahead:

Classes
class	Collect
class	Replace
class	ReplacementMap

Public Member Functions
	ConvertLookahead (P4::ReferenceMap *refMap, P4::TypeMap *typeMap, DpdkProgramStructure *s)

Public Attributes
ReplacementMap	repl

Detailed Description

DPDK target supports lookahead instruction only with header operand. This pass transforms usage of lookahead method with type parameters of other than header type (IR::Type_Header) to lookahead with header type using the following transformation:

This parser code:

T var_name;

state state_name { var_name = pkt.lookahead<T>(); }

is transformed to this:

• new header definition:

header lookahead_tmp_hdr { T f; }

• modification in parser code:

T var_name; lookahead_tmp_hdr lookahead_tmp;

state state_name { lookahead_tmp = pkt.lookahead<lookahead_tmp_hdr>(); var_name = lookahead_tmp; }