ref: 42dfac6916ebbdac65cbec8b3e1a80c3ee41423c
dir: /appl/lib/slip.b/
implement Filter; include "sys.m"; include "filter.m"; End: con byte 8r300; Esc: con byte 8r333; Eend: con byte 8r334; # encoded End byte Eesc: con byte 8r335; # encoded Esc byte init() { } start(param: string): chan of ref Rq { req := chan of ref Rq; if(param == "encode") spawn encode(req); else spawn decode(req); return req; } encode(reqs: chan of ref Rq) { sys := load Sys Sys->PATH; reqs <-= ref Rq.Start(sys->pctl(0, nil)); buf := array[8192] of byte; rc := chan of int; do{ reqs <-= ref Rq.Fill(buf, rc); if((n := <-rc) <= 0){ if(n == 0) reqs <-= ref Rq.Finished(nil); break; } b := array[2*n + 2] of byte; # optimise time not space o := 1; b[0] = End; for(i := 0; i < n; i++){ if((c := buf[i]) == End || c == Esc){ b[o++] = Esc; c = byte (Eend + (c& byte 1)); } b[o++] = c; } b[o++] = End; if(o != len b) b = b[0:o]; reqs <-= ref Rq.Result(b, rc); }while(<-rc != -1); } Slipesc, Slipend: con (1<<8) + iota; Slipsize: con 1006; # rfc's suggestion slipin(c: byte, esc: int): int { if(esc == Slipesc){ # last byte was Esc if(c == Eend) c = End; else if(c == Eesc) c = Esc; }else{ if(c == Esc) return Slipesc; if(c == End) return Slipend; } return int c; } decode(reqs: chan of ref Rq) { sys := load Sys Sys->PATH; reqs <-= ref Rq.Start(sys->pctl(0, nil)); buf := array[8192] of byte; b := array[Slipsize] of byte; rc := chan of int; c := 0; o := 0; for(;;){ reqs <-= ref Rq.Fill(buf, rc); if((n := <-rc) <= 0){ if(n < 0) exit; break; } for(i := 0; i < n; i++){ c = slipin(buf[i], c); if(c == Slipend){ if(o != 0){ reqs <-= ref Rq.Result(b[0:o], rc); if(<-rc == -1) exit; b = array[Slipsize] of byte; o = 0; } }else if(c != Slipesc){ if(o >= len b){ t := array[3*len b/2] of byte; t[0:] = b; b = t; } b[o++] = byte c; } } } # partial block discarded reqs <-= ref Rq.Finished(nil); }