diff --git a/encodings/dbcs-data.js b/encodings/dbcs-data.js
index 2bf7415..c3dc05d 100644
--- a/encodings/dbcs-data.js
+++ b/encodings/dbcs-data.js
@@ -3,13 +3,21 @@
 // Description of supported double byte encodings and aliases.
 // Tables are not require()-d until they are needed to speed up library load.
 // require()-s are direct to support Browserify.
+var savedGbkTable
+var gbkTableGetter = function() {
+  if (savedGbkTable) {
+    return savedGbkTable
+  }
+  savedGbkTable = require('./tables/cp936.json').concat(require('./tables/gbk-added.json'))
+  return savedGbkTable
+}
 
 module.exports = {
-    
+
     // == Japanese/ShiftJIS ====================================================
     // All japanese encodings are based on JIS X set of standards:
     // JIS X 0201 - Single-byte encoding of ASCII + ¥ + Kana chars at 0xA1-0xDF.
-    // JIS X 0208 - Main set of 6879 characters, placed in 94x94 plane, to be encoded by 2 bytes. 
+    // JIS X 0208 - Main set of 6879 characters, placed in 94x94 plane, to be encoded by 2 bytes.
     //              Has several variations in 1978, 1983, 1990 and 1997.
     // JIS X 0212 - Supplementary plane of 6067 chars in 94x94 plane. 1990. Effectively dead.
     // JIS X 0213 - Extension and modern replacement of 0208 and 0212. Total chars: 11233.
@@ -27,7 +35,7 @@ module.exports = {
     //               0x8F, (0xA1-0xFE)x2 - 0212 plane (94x94).
     //  * JIS X 208: 7-bit, direct encoding of 0208. Byte ranges: 0x21-0x7E (94 values). Uncommon.
     //               Used as-is in ISO2022 family.
-    //  * ISO2022-JP: Stateful encoding, with escape sequences to switch between ASCII, 
+    //  * ISO2022-JP: Stateful encoding, with escape sequences to switch between ASCII,
     //                0201-1976 Roman, 0208-1978, 0208-1983.
     //  * ISO2022-JP-1: Adds esc seq for 0212-1990.
     //  * ISO2022-JP-2: Adds esc seq for GB2313-1980, KSX1001-1992, ISO8859-1, ISO8859-7.
@@ -77,7 +85,9 @@ module.exports = {
     'isoir58': 'gbk',
 
     // Microsoft's CP936 is a subset and approximation of GBK.
-    // TODO: Euro = 0x80 in cp936, but not in GBK (where it's valid but undefined)
+    // Euro = 0x80 in cp936, but not in GBK (where it's valid but undefined)
+    // We could be able to decode Euro(0x80) in any of CP936/GBK/GB18030
+    // But we would not encoding it to 0x80 when the codec is GB18030 or encodeEuro === true option in decode option
     'windows936': 'cp936',
     '936': 'cp936',
     'cp936': {
@@ -88,20 +98,19 @@ module.exports = {
     // GBK (~22000 chars) is an extension of CP936 that added user-mapped chars and some other.
     'gbk': {
         type: '_dbcs',
-        table: function() { return require('./tables/cp936.json').concat(require('./tables/gbk-added.json')) },
+        table: gbkTableGetter,
     },
     'xgbk': 'gbk',
 
     // GB18030 is an algorithmic extension of GBK.
     'gb18030': {
         type: '_dbcs',
-        table: function() { return require('./tables/cp936.json').concat(require('./tables/gbk-added.json')) },
+        table: gbkTableGetter,
         gb18030: function() { return require('./tables/gb18030-ranges.json') },
     },
 
     'chinese': 'gb18030',
 
-    // TODO: Support GB18030 (~27000 chars + whole unicode mapping, cp54936)
     // http://icu-project.org/docs/papers/gb18030.html
     // http://source.icu-project.org/repos/icu/data/trunk/charset/data/xml/gb-18030-2000.xml
     // http://www.khngai.com/chinese/charmap/tblgbk.php?page=0
@@ -133,7 +142,7 @@ module.exports = {
     //  * Windows CP 951: Microsoft variant of Big5-HKSCS-2001. Seems to be never public. http://me.abelcheung.org/articles/research/what-is-cp951/
     //  * Big5-2003 (Taiwan standard) almost superset of cp950.
     //  * Unicode-at-on (UAO) / Mozilla 1.8. Falling out of use on the Web. Not supported by other browsers.
-    //  * Big5-HKSCS (-2001, -2004, -2008). Hong Kong standard. 
+    //  * Big5-HKSCS (-2001, -2004, -2008). Hong Kong standard.
     //    many unicode code points moved from PUA to Supplementary plane (U+2XXXX) over the years.
     //    Plus, it has 4 combining sequences.
     //    Seems that Mozilla refused to support it for 10 yrs. https://bugzilla.mozilla.org/show_bug.cgi?id=162431 https://bugzilla.mozilla.org/show_bug.cgi?id=310299
@@ -144,7 +153,7 @@ module.exports = {
     //    In the encoder, it might make sense to support encoding old PUA mappings to Big5 bytes seq-s.
     //    Official spec: http://www.ogcio.gov.hk/en/business/tech_promotion/ccli/terms/doc/2003cmp_2008.txt
     //                   http://www.ogcio.gov.hk/tc/business/tech_promotion/ccli/terms/doc/hkscs-2008-big5-iso.txt
-    // 
+    //
     // Current understanding of how to deal with Big5(-HKSCS) is in the Encoding Standard, http://encoding.spec.whatwg.org/#big5-encoder
     // Unicode mapping (http://www.unicode.org/Public/MAPPINGS/OBSOLETE/EASTASIA/OTHER/BIG5.TXT) is said to be wrong.