Remote Procedure Call BYU ACM {pageName}}远程过程调用杨百翰大学ACM { { } }而.pptVIP

Presentation Formatting Overview Marshalling (encoding) application data into messages Unmarshalling (decoding) messages into application data Data Types Data types we consider: integers floating point numbers character strings arrays structures Types of data we do not consider (now): images video multimedia documents Difficulties Representation of base types floating point: IEEE 754 versus non-standard integer: big-endian versus little-endian Compiler layout of structures Taxonomy Data types base types (e.g., ints, floats); must convert flat types (e.g., structures, arrays); must pack complex types (e.g., pointers); must linearize Conversion Strategy canonical intermediate form receiver-makes-right (an N x N solution) N machine architectures must be able to handle N representations Marshalling Tagged versus Untagged data Stubs compiled interpreted CORBA Examples XDR: eXternal Data Representation Defined by Sun for use with SunRPC C type system (without function pointers) Canonical intermediate form Untagged (except array length) Compiled stubs #define MAXNAME 256; #define MAXLIST 100; struct item { int count; char name[MAXNAME]; int list[MAXLIST]; }; bool_t xdr_item(XDR *xdrs, struct item *ptr) { return(xdr_int(xdrs, ptr-count) xdr_string(xdrs, ptr-name,MAXNAME) xdr_array(xdrs, ptr-list, ptr-count, MAXLIST, sizeof(int), xdr_int)); } XDR Abstract Syntax Notation ASN.1 (tag-8 bits, length-8+bits, value) Used by Simple Network Management Protocol (SNMP) Canonical Intermediate form Length=0x82 01 01=257 Each call sends 3 bytes NDR: Network Data Representation Defined by DCE (CORBA) Essentially the C type system Receiver-makes-right (architecture tag) Individual data items untagged Compiled stubs from Interface Definition Language (IDL) 4-byte architecture definition tag IntegrRep 0 = big-endian 1 = little-endian CharRep 0 = ASCII 1 = EBCDIC FloatRep 0 = IEEE 754 1 = VAX 2 = Cray 3 = IBM Remote Procedure Calls Overview Mechanics Address Space for P