luci-base: add client-side prng library

Introduce a new tools.prng JS library which implements the musl libc
srand() and rand() calls to produce identical pseudo random number
sequences in the browser which is needed for the string to color
conversion later on.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

modules/luci-base/htdocs/luci-static/resources/tools/prng.js

@@ -0,0 +1,93 @@
+'use strict';
+
+var s = [0x0000, 0x0000, 0x0000, 0x0000];
+
+function mul(a, b) {
+	var r = [0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000];
+
+	for (var j = 0; j < 4; j++) {
+		var k = 0;
+		for (var i = 0; i < 4; i++) {
+			var t = a[i] * b[j] + r[i+j] + k;
+			r[i+j] = t & 0xffff;
+			k = t >>> 16;
+		}
+		r[j+4] = k;
+	}
+
+	r.length = 4;
+
+	return r;
+}
+
+function add(a, n) {
+	var r = [0x0000, 0x0000, 0x0000, 0x0000],
+	    k = n;
+
+	for (var i = 0; i < 4; i++) {
+		var t = a[i] + k;
+		r[i] = t & 0xffff;
+		k = t >>> 16;
+	}
+
+	return r;
+}
+
+function shr(a, n) {
+	var r = [a[0], a[1], a[2], a[3], 0x0000],
+	    i = 4,
+	    k = 0;
+
+	for (; n > 16; n -= 16, i--)
+		for (var j = 0; j < 4; j++)
+			r[j] = r[j+1];
+
+	for (; i > 0; i--) {
+		var s = r[i-1];
+		r[i-1] = (s >>> n) | k;
+		k = ((s & ((1 << n) - 1)) << (16 - n));
+	}
+
+	r.length = 4;
+
+	return r;
+}
+
+return L.Class.extend({
+	seed: function(n) {
+		n = (n - 1)|0;
+		s[0] = n & 0xffff;
+		s[1] = n >>> 16;
+		s[2] = 0;
+		s[3] = 0;
+	},
+
+	int: function() {
+		s = mul(s, [0x7f2d, 0x4c95, 0xf42d, 0x5851]);
+		s = add(s, 1);
+
+		var r = shr(s, 33);
+		return (r[1] << 16) | r[0];
+	},
+
+	get: function() {
+		var r = (this.int() % 0x7fffffff) / 0x7fffffff, l, u;
+
+		switch (arguments.length) {
+		case 0:
+			return r;
+
+		case 1:
+			l = 1;
+			u = arguments[0]|0;
+			break;
+
+		case 2:
+			l = arguments[0]|0;
+			u = arguments[1]|0;
+			break;
+		}
+
+		return Math.floor(r * (u - l + 1)) + l;
+	}
+});