First upload

engines/subleq.awk

@@ -0,0 +1,40 @@
+#!/sbin/env awk -f
+# POSIX AWK port of Subleq VM (16-bit variant)
+# Accepts .dec files as input
+# Usage: [busybox] awk -f subleq.awk program.dec
+# Created by Luxferre in 2023, released into public domain
+
+function L(v) { # cast any value to unsigned 16-bit integer
+  v = int(v)
+  while(v < 0) v += 65536
+  return int(v%65536)
+}
+
+function getchar(c, cmd) { # POSIX-compatible getchar emulation with sh read
+  (cmd="c='';IFS= read -r -n 1 -d $'\\0' c;printf '%u' \"'$c\"") | getline c
+  close(cmd)
+  return int(c)
+}
+
+BEGIN {
+  for(pc=0;pc<65536;pc++) MEM[pc] = 0 # init the memory array
+  pc = a = b = c = 0 # reset the program counter and other vars
+}
+
+# match on any 16-bit signed integer in the .dec file
+{ for(i=1;i<=NF;i++) if($i ~ /^[-0-9][0-9]*$/) MEM[pc++] = L($i) }
+
+END { # start the actual execution
+  for(pc=0;pc<32768;) {
+    a = MEM[pc++]; b = MEM[pc++]; c = MEM[pc++] # fill the cell addresses
+    # -1 in cell A => input to cell B
+    if(a == 65535) MEM[b] = L(getchar())
+    # -1 in cell B => output cell A
+    else if(b == 65535) printf("%c", MEM[a]%256)
+    # main OISC logic here
+    else {
+      MEM[b] = L(MEM[b] - MEM[a]) # subtract the first 2 cells and cast
+      if(MEM[b] == 0 || (MEM[b] > 32767)) pc = c # jump if result <=0 
+    }
+  }
+}