From dc18fc34c6fd6a13d15597b5e9f95e57d8eb7fea Mon Sep 17 00:00:00 2001
From: fab <fabrice.leal.ch@gmail.com>
Date: Wed, 2 Jan 2019 21:18:45 +0000
Subject: more portable functions

---
 lib/js/urweb.js | 94 +++++++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 81 insertions(+), 13 deletions(-)

diff --git a/lib/js/urweb.js b/lib/js/urweb.js
index 931ab1f5..2a621a2d 100644
--- a/lib/js/urweb.js
+++ b/lib/js/urweb.js
@@ -7,6 +7,60 @@ function needsDynPrefix() {
     return scripts.length == 0;
 }
 
+if (!String.fromCodePoint) {
+    String.fromCodePoint = function () {
+	var chars = [], i;
+	for(i = 0; i < arguments.length; ++i) {
+	    var c = Number(arguments[i]);
+	    if (!isFinite(c) || c < 0 || c > 0x10FFFF || Math.floor(c) !== c) {
+		throw new RangeError("Invalid code point " + c);
+	    }
+	    if (c < 0x10000) {
+		chars.push(c);
+	    } else {
+		c -= 0x10000;
+		chars.push((c >> 10) + 0xD800);
+		chars.push((c % 0x400) + 0xDC00);
+	    }
+	}
+	return String.fromCharCode.apply(undefined, chars);
+    };
+
+    String.prototype.codePointAt = function (index) {
+	var str = String(this);
+	if (index < 0 || index >= str.length) {
+	    return undefined;
+	}
+	var first = str.charCodeAt(index);
+	if (first >= 0xD800 && first <= 0xDBFF && str.length > index + 1) {
+	    var second = str.charCodeAt(index + 1);
+	    if (second >= 0xDC00 && second <= 0xDFFF) {
+		return ((first - 0xD800) << 10) + (second - 0xDC00) + 0x10000;
+	    }
+	}
+	return first;
+    };
+}
+
+function iterateString(s, fn) {
+    var strIdx = 0, idx = 0, res, cp;
+    for (; strIdx < s.length ;) {
+	cp = s.codePointAt(strIdx);
+	if (fn) {	    
+	    res = fn(String.fromCodePoint(cp), idx, strIdx);
+	    if (res === false) return;
+	}
+	strIdx += cp > 0xFFFF ? 2 : 1;
+	++idx;
+    }
+}
+
+function strSplit(s) {
+    var chars = [];
+    iterateString(s, function(c) { chars.push(c); });
+    return chars;
+}
+
 var dynPrefix = needsDynPrefix() ? "<span style=\"display:none\">A</span>" : "";
 
 // Function versions of operators
@@ -2438,11 +2492,24 @@ function s2b(s) { return s == "True" ? true : s == "False" ? false : null; }
 function s2be(s) { return s == "True" ? true : s == "False" ? false : er("Illegal Boolean " ^ s); }
 
 function id(x) { return x; }
-function sub(s, i) { return Array.from(s)[i]; }
-function suf(s, i) { return Array.from(s).slice(i).join(""); }
-function slen(s) { return Array.from(s).length; }
+function sub(s, i) {
+    var ch = undefined;
+    iterateString(s, function(c, idx) { if (idx == i) { ch = c; return false; }});
+    return ch;
+}
+function suf(s, i) {
+    var offset = s.length;
+    iterateString(s, function(_, idx, sidx) { if (idx == i) { off = sidx; return false; } });
+    return s.substring(offset);
+}
+function slen(s) {
+    var len = 0;
+    iterateString(s, function(){ ++len;});
+    return len;
+}
 function sidx(s, ch) {
-    var r = Array.from(s).indexOf(ch);
+    var r = -1;
+    iterateString(s, function(c, idx){ if (c == ch) { r = idx; return false; } });
     if (r == -1)
         return null;
     else
@@ -2450,8 +2517,8 @@ function sidx(s, ch) {
 }
 function ssidx(h, n) {
     if (n == "") return 0;
-    var ah = Array.from(h);
-    var an = Array.from(n);
+    var ah = strSplit(h);
+    var an = strSplit(n);
     var i = 0, y = 0;
     var top = ah.length - an.length + 1;
     if (top < 0) top = 0;
@@ -2474,8 +2541,8 @@ function ssidx(h, n) {
 }
 
 function sspn(s, chs) {
-    var s2 = Array.from(s);
-    var chs2 = Array.from(chs);
+    var s2 = strSplit(s);
+    var chs2 = strSplit(chs);
     
     for (var i = 0; i < s2.length; ++i)
         if (chs2.indexOf(s2[i]) != -1)
@@ -2483,6 +2550,7 @@ function sspn(s, chs) {
 
     return s2.length;
 }
+
 function schr(s, ch) {
     var r = s.indexOf(ch);
     if (r == -1)
@@ -2491,7 +2559,7 @@ function schr(s, ch) {
         return s.substring(r);
 }
 function ssub(s, start, len) {
-    return Array.from(s).slice(start, start+len).join("");
+    return strSplit(s).slice(start, start+len).join("");
 }
 function strlenGe(s, len) {
     return slen(s) >= len;
@@ -3228,7 +3296,7 @@ function bless(s) {
 var maxCh = chr(127);
 
 function blessData(s) {
-    var chars = Array.from(s);
+    var chars = strSplit(s);
     
     for (var i = 0; i < chars.length; ++i) {
         var c = chars[i];
@@ -3243,7 +3311,7 @@ function blessData(s) {
 // CSS validation
 
 function atom(s) {
-    var chars = Array.from(s);
+    var chars = strSplit(s);
     
     for (var i = 0; i < chars.length; ++i) {
         var c = chars[i];
@@ -3255,7 +3323,7 @@ function atom(s) {
 }
 
 function css_url(s) {
-    var chars = Array.from(s);
+    var chars = strSplit(s);
     
     for (var i = 0; i < chars.length; ++i) {
         var c = chars[i];
@@ -3268,7 +3336,7 @@ function css_url(s) {
 }
 
 function property(s) {
-    var chars = Array.from(s);
+    var chars = strSplit(s);
     
     if (chars.length <= 0)
         er("Empty CSS property");
-- 
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