From 90649345e011cdb998efe216f5e94a38d81eb4d2 Mon Sep 17 00:00:00 2001
From: daurnimator <quae@daurnimator.com>
Date: Sun, 7 Jan 2018 01:43:59 +1100
Subject: Avoid String.fromCodePoint (IE compat)

---
 src/defs.js     | 23 +++++++++++++++++------
 src/lobject.js  |  7 +++++--
 src/lutf8lib.js |  3 ++-
 3 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/src/defs.js b/src/defs.js
index e5ffe35..b96dcf5 100644
--- a/src/defs.js
+++ b/src/defs.js
@@ -173,11 +173,10 @@ const to_jsstring = function(value, from, to) {
 
     let str = "";
     for (let i = (from!==void 0?from:0); i < to;) {
-        let u;
         let u0 = value[i++];
         if (u0 < 0x80) {
             /* single byte sequence */
-            u = u0;
+            str += String.fromCharCode(u0);
         } else if (u0 < 0xC2 || u0 > 0xF4) {
             throw RangeError("cannot convert invalid utf8 to javascript string");
         } else if (u0 <= 0xDF) {
@@ -185,7 +184,7 @@ const to_jsstring = function(value, from, to) {
             if (i >= to) throw RangeError("cannot convert invalid utf8 to javascript string");
             let u1 = value[i++];
             if ((u1&0xC0) !== 0x80) throw RangeError("cannot convert invalid utf8 to javascript string");
-            u = ((u0 & 0x1F) << 6) + (u1 & 0x3F);
+            str += String.fromCharCode(((u0 & 0x1F) << 6) + (u1 & 0x3F));
         } else if (u0 <= 0xEF) {
             /* three byte sequence */
             if (i+1 >= to) throw RangeError("cannot convert invalid utf8 to javascript string");
@@ -193,7 +192,15 @@ const to_jsstring = function(value, from, to) {
             if ((u1&0xC0) !== 0x80) throw RangeError("cannot convert invalid utf8 to javascript string");
             let u2 = value[i++];
             if ((u2&0xC0) !== 0x80) throw RangeError("cannot convert invalid utf8 to javascript string");
-            u = ((u0 & 0x0F) << 12) + ((u1 & 0x3F) << 6) + (u2 & 0x3F);
+            let u = ((u0 & 0x0F) << 12) + ((u1 & 0x3F) << 6) + (u2 & 0x3F);
+            if (u <= 0xFFFF) { /* BMP codepoint */
+                str += String.fromCharCode(u);
+            } else { /* Astral codepoint */
+                u -= 0x10000;
+                let s1 = (u >> 10) + 0xD800;
+                let s2 = (u % 0x400) + 0xDC00;
+                str += String.fromCharCode(s1, s2);
+            }
         } else {
             /* four byte sequence */
             if (i+2 >= to) throw RangeError("cannot convert invalid utf8 to javascript string");
@@ -203,9 +210,13 @@ const to_jsstring = function(value, from, to) {
             if ((u2&0xC0) !== 0x80) throw RangeError("cannot convert invalid utf8 to javascript string");
             let u3 = value[i++];
             if ((u3&0xC0) !== 0x80) throw RangeError("cannot convert invalid utf8 to javascript string");
-            u = ((u0 & 0x07) << 18) + ((u1 & 0x3F) << 12) + ((u2 & 0x3F) << 6) + (u3 & 0x3F);
+            /* Has to be astral codepoint */
+            let u = ((u0 & 0x07) << 18) + ((u1 & 0x3F) << 12) + ((u2 & 0x3F) << 6) + (u3 & 0x3F);
+            u -= 0x10000;
+            let s1 = (u >> 10) + 0xD800;
+            let s2 = (u % 0x400) + 0xDC00;
+            str += String.fromCharCode(s1, s2);
         }
-        str += String.fromCodePoint(u);
     }
     return str;
 };
diff --git a/src/lobject.js b/src/lobject.js
index bd10be8..b5d4a96 100644
--- a/src/lobject.js
+++ b/src/lobject.js
@@ -607,9 +607,12 @@ const luaO_pushvfstring = function(L, fmt, argp) {
                 }
                 break;
             }
-            case char['U']:
-                pushstr(L, defs.to_luastring(String.fromCodePoint(argp[a++])));
+            case char['U']: {
+                let buff = new Uint8Array(UTF8BUFFSZ);
+                let l = luaO_utf8esc(buff, argp[a++]);
+                pushstr(L, buff.subarray(UTF8BUFFSZ - l));
                 break;
+            }
             case char['%']:
                 pushstr(L, defs.to_luastring("%", true));
                 break;
diff --git a/src/lutf8lib.js b/src/lutf8lib.js
index 722d9f1..58533cf 100644
--- a/src/lutf8lib.js
+++ b/src/lutf8lib.js
@@ -76,10 +76,11 @@ const utflen = function(L) {
     return 1;
 };
 
+const p_U = lua.to_luastring("%U");
 const pushutfchar = function(L, arg) {
     let code = lauxlib.luaL_checkinteger(L, arg);
     lauxlib.luaL_argcheck(L, 0 <= code && code <= MAXUNICODE, arg, lua.to_luastring("value out of range", true));
-    lua.lua_pushstring(L, lua.to_luastring(String.fromCodePoint(code)));
+    lua.lua_pushfstring(L, p_U, code);
 };
 
 /*
-- 
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