Initial idea sketch for a C-based VolksForth core.

portable/README.md

@@ -0,0 +1,5 @@
+# Idea for a "C-VolksForth"
+
+So far anything in this directory is just an early idea for a C-based
+core of a VolksForth variant that could be compiled and run on any
+platform with a C compiler, e.g. Linux.

portable/core.c

@@ -0,0 +1,62 @@
+
+// This is only a sketch of an idea yet.
+
+
+byte core[0x10000];
+
+uint16 ip;
+uint16 w;
+
+void run() {
+  while (true) {
+    next();
+  }
+}
+
+void next() {
+  w = *((uint16*) core + ip);
+  ip += 2;
+  byte opcode = core[w];
+  // on second thought, the above looks more like direct threaded,
+  // which is maybe not what we want in a C core for VolksForth.
+  // Or is it?
+  process(opcode);
+}
+
+void process(byte opcode) {
+  if (opcode & 0xc0) {
+    // handle special opcode
+    // This is assuming we won’t have more than 64 C primitives,
+    // and might have use for a few
+    // opcodes with inlined parameters. Not sure about this, though.
+  } else {
+    jumptable[opcode]();
+  }
+}
+
+void jumptable[0x40]() = {
+  nest, unnest, dup, drop, plus, emit
+};
+
+void nest() {
+  rs[rp++] = ip;
+  ip = w + 2;
+}
+
+void unnest() {
+  ip = rs[--rp];
+}
+
+void dup() {
+  uint16 = s[sp];
+  s[++sp] = uint16;
+}
+
+void emit() {
+  putc(s[sp--]);
+}
+
+void plus() {
+  a = s[sp--];
+  s[sp] += a;
+}