add random non-overlapping ranges in core

1 files changed, 66 insertions, 6 deletions

diff --git a/src/vm/core.js b/src/vm/core.js
index 4fdd0a0..184be00 100644
--- a/src/vm/core.js
+++ b/src/vm/core.js
@@ -3,6 +3,46 @@
 const { Op, AddrMode} = require('./enum.js');
 
 
+function mod(a, N) {
+	const A = a % N;
+	if (A < 0) {
+		return A + N;
+	} else {
+		return A;
+	}
+}
+
+
+class Range {
+	constructor(start, end, coresize) {
+		this.start = start;
+		this.end = end;
+		this.coresize = coresize;
+	}
+
+	
+	// thanks to https://fgiesen.wordpress.com/2015/09/24/intervals-in-modular-arithmetic/
+	// c:
+	contains(n) {
+		return mod(n - this.start, this.coresize) <= mod(this.end - this.start, this.coresize);
+	}
+
+	overlaps(other) {
+		return (
+			this.contains(other.start) ||
+			other.contains(this.start)
+		);
+	}
+}
+
+
+function randomRange(coresize, length) {
+	const start = Math.floor(Math.random() * coresize);
+	const end = mod(start + length - 1, coresize);
+	return new Range(start, end, coresize);
+}
+
+
 class Core {
 	constructor(size) {
 		this.data = new Array(size);
@@ -18,13 +58,31 @@ class Core {
 	}
 
 
-	normalize(pc, value) {
-		const v = (pc + value) % this.data.length;
-		if (v < 0) {
-			return v + this.data.length;
-		} else {
-			return v;
+	getRanges(lengths, ranges) {
+		if (ranges === undefined) {
+			ranges = [];
+		}
+
+		if (lengths.length === 0) {
+			return ranges;
 		}
+
+		const length = lengths[0];
+		let range;
+		do {
+			range = randomRange(this.data.length, length);
+		} while (
+			ranges
+				.map(r => r.overlaps(range))
+				.reduce((acc, overlap) => acc || overlap, false)
+		);
+
+		return this.getRanges(lengths.slice(1), [...ranges, range]);
+	}
+
+
+	normalize(pc, value) {
+		return mod((pc + value), this.data.length);
 	}
 
 
@@ -57,4 +115,6 @@ class Core {
 }
 
 
+exports.mod = mod;
+exports.Range = Range;
 exports.Core = Core;