PACKET cluster DEFINES                       (* Copyright (C) 1986 *)
                                             (* Frank Klapper      *)
                                             (* 19.03.86           *)

  CLUSTER, 
  :=, 
  text,
  text 32,            (* typical dir entry *)
  write text,
  write text 32,
  reduce cluster buffer:
 
LET max cluster size = 8192;   (* 8192 * 8 = 64 KB *)

TYPE CLUSTER = BOUND STRUCT (ALIGN dummy, 
                             ROW max cluster size REAL cluster row); 
 
TEXT VAR string;
INT VAR string length;
 
INT VAR sector no, eight byte pos, index;

reduce cluster buffer;

.reals per sector:        sector size DIV 8.
.reals per std eu sector: 512 DIV 8.

PROC reduce cluster buffer:
  string := 32 * "*";
  string length := 32.

END PROC reduce cluster buffer;

OP := (CLUSTER VAR cluster, DATASPACE VAR ds):
  CONCR (cluster) := ds 
 
END OP :=; 
 
TEXT PROC text (CLUSTER CONST cluster, INT CONST from, to):
  init string;
  FOR sector no FROM 0 UPTO sectors per cluster - 1 REP
    get text of sector
  PER;
  subtext (string, from, to).
 
init string:
  IF string length < cluster size
    THEN string := cluster size * "*";
         string length := cluster size
  FI.

get text of sector:
  FOR eight byte pos FROM 1 UPTO reals per sector REP
    replace (string, string index, cluster.cluster row [row index]) 
  PER.

string index:
  reals per sector * sector no + eight byte pos.

row index:
  reals per std eu sector * sector no + eight byte pos.

END PROC text;

TEXT PROC text 32 (CLUSTER CONST cluster, INT CONST part):
  FOR index FROM 1 UPTO 4 REP
    replace (string, index, cluster.cluster row [index + 4 * part])
  PER;
  subtext (string, 1, 32).
 
END PROC text 32;

PROC write text (CLUSTER VAR cluster,
                 TEXT CONST string):
  IF LENGTH string < cluster size
    THEN execute write text (cluster, text (string, cluster size))
    ELSE execute write text (cluster, string)
  FI.

END PROC write text;

PROC execute write text (CLUSTER VAR cluster,
                         TEXT CONST string):
  FOR sector no FROM 0 UPTO sectors per cluster - 1 REP
    write text of sector
  PER.

write text of sector:
  FOR eight byte pos FROM 1 UPTO reals per sector REP
    cluster.cluster row [row index] := string RSUB (string index) 
  PER.

row index:
  reals per std eu sector * sector no + eight byte pos.

string index:
  reals per sector * sector no + eight byte pos.


END PROC execute write text;

PROC write text 32 (CLUSTER VAR cluster, TEXT CONST string, INT CONST part):
  FOR index FROM 1 UPTO 4 REP
    cluster.cluster row [index + 4 * part] := string RSUB (index)
  PER;

END PROC write text 32;

END PACKET cluster;