begin writing vm

1 files changed, 51 insertions, 0 deletions

diff --git a/src/vm/core.js b/src/vm/core.js
new file mode 100644
index 0000000..292ceb0
--- /dev/null
+++ b/src/vm/core.js
@@ -0,0 +1,51 @@
+'use strict';
+
+const { Op, AddrMode} = require('./enum.js');
+
+
+class Core {
+	constructor(size) {
+		this.data = new Array(size);
+
+		// initialize core to all DAT 0, 0
+		for (let i=0; i<size; i++) {
+			this.data[i] = {
+				opcode: Op.DAT,
+				a: { value: 0, mode: AddrMode.Direct },
+				b: { value: 0, mode: AddrMode.Direct },
+			};
+		}
+	}
+
+
+	normalize(pc, value) {
+		return (pc + value) % this.data.length;
+	}
+
+
+	getLocation(pc, address) {
+		switch(address.mode) {
+			case AddrMode.Immediate:
+				throw "Cannot get location from immediate-mode address";
+			case AddrMode.Direct:
+				return this.normalize(pc, address.value);
+			case AddrMode.Indirect: {
+				let loc = this.normalize(pc, address.value);
+				let b = this.data[loc];
+				return this.normalize(loc, b);
+			}
+			case AddrMode.Predecrement: {
+				let loc = this.normalize(pc, address.value);
+				this.data[loc].b -= 1;
+				let b = this.data[loc].b;
+				return this.normalize(loc, b);
+			}
+			default:
+				throw `Invalid addressing mode "${address.mode}"`;
+		}
+	}
+
+	getValue(pc, address) {
+		return this.data[this.getLocation(pc, address)];
+	}
+}