diff --git a/unicode.cpp b/unicode.cpp
index 233dae564..9abf83d34 100644
--- a/unicode.cpp
+++ b/unicode.cpp
@@ -224,138 +224,109 @@ static std::vector<size_t> unicode_regex_split_custom_gpt2(const std::string & t
     std::vector<size_t> bpe_offsets; // store the offset of each word
     bpe_offsets.reserve(offsets.size()); // Reserve memory for the approximate size
 
-    size_t start = 0;
-
     const auto cpts = unicode_cpts_from_utf8(text);
 
+    size_t start = 0;
     for (auto offset : offsets) {
-        std::string token;
 
-        bool collecting_numeric = false;
-        bool collecting_letter = false;
-        bool collecting_special = false;
-        bool collecting_whitespace_lookahead = false;
-        bool collecting = false;
+        const size_t offset_ini = start;
+        const size_t offset_end = start + offset;
+        assert(offset_end <= cpts.size());
+        start = offset_end;
 
-        std::vector<std::string> text_utf;
-        text_utf.reserve(offset);
+        auto _get_cpt = [&] (const size_t pos) -> char32_t {
+            return (offset_ini <= pos && pos < offset_end) ? cpts[pos] : 0;
+        };
 
-        for (size_t i = start; i < start + offset; ++i) {
-            text_utf.emplace_back(unicode_cpt_to_utf8(cpts[i]));
-        }
+        auto _get_cpt_type = [&] (const size_t pos) -> int {
+            return (offset_ini <= pos && pos < offset_end) ? unicode_cpt_type(cpts[pos]) : CODEPOINT_TYPE_UNIDENTIFIED;
+        };
 
-        for (int i = 0; i < (int)text_utf.size(); i++) {
-            const std::string & utf_char = text_utf[i];
-            bool split_condition = false;
-            int bytes_remain = text_utf.size() - i;
+        size_t _prev_end = offset_ini;
+        auto _add_token = [&] (const size_t end) -> size_t {
+            assert(_prev_end <= end && end <= offset_end);
+            size_t len = end - _prev_end;
+            if(len > 0)
+                bpe_offsets.push_back(len);
+            _prev_end = end;
+            //if(len) {
+            //    std::string s = "";
+            //    for(size_t p = end-len; p < end; p++)
+            //        s += unicode_cpt_to_utf8(cpts[p]);
+            //    printf(">>> '%s'\n", s.c_str());
+            //}
+            return len;
+        };
 
-            // forward backward lookups
-            const std::string & utf_char_next      = (i + 1 < (int)text_utf.size()) ? text_utf[i + 1] : "";
-            const std::string & utf_char_next_next = (i + 2 < (int)text_utf.size()) ? text_utf[i + 2] : "";
+        for(size_t pos = offset_ini; pos < offset_end; /*pos++*/ ) {
+            const char32_t cpt = _get_cpt(pos);
+            const int cpt_type = _get_cpt_type(pos);
 
-            // handling contractions
-            if (!split_condition && bytes_remain >= 2) {
-                // 's|'t|'m|'d
-                if (utf_char == "\'" && (utf_char_next == "s" || utf_char_next == "t" || utf_char_next == "m" || utf_char_next == "d")) {
-                    split_condition = true;
-                }
-                if (split_condition) {
-                    if (token.size()) {
-                        bpe_offsets.emplace_back(unicode_cpts_from_utf8(token).size());
-                    }
-                    token = utf_char + utf_char_next;
-                    bpe_offsets.emplace_back(unicode_cpts_from_utf8(token).size());
-                    token = "";
-                    i++;
+            // regex: 's|'t|'re|'ve|'m|'ll|'d
+            if (cpt == '\'' && pos+1 < offset_end) {
+                char32_t cpt_next = _get_cpt(pos+1);
+                if (cpt_next == 's' || cpt_next == 't' || cpt_next == 'm' || cpt_next == 'd') {
+                    pos += _add_token(pos+2);
                     continue;
-                }
-            }
-            if (!split_condition && bytes_remain >= 3) {
-                // 're|'ve|'ll
-                if (utf_char == "\'" && (
-                    (utf_char_next == "r" && utf_char_next_next == "e") ||
-                    (utf_char_next == "v" && utf_char_next_next == "e") ||
-                    (utf_char_next == "l" && utf_char_next_next == "l"))
-                    ) {
-                    split_condition = true;
-                }
-                if (split_condition) {
-                    // current token + next token can be defined
-                    if (token.size()) {
-                        bpe_offsets.emplace_back(unicode_cpts_from_utf8(token).size());
+                } else if (pos+2 < offset_end) {
+                    char32_t cpt_next_next = _get_cpt(pos+2);
+                    if ((cpt_next == 'r' && cpt_next_next == 'e') ||
+                        (cpt_next == 'v' && cpt_next_next == 'e') ||
+                        (cpt_next == 'l' && cpt_next_next == 'l')) {
+                        pos += _add_token(pos+3);
+                        continue;
                     }
-                    token =  utf_char;
-                    token += utf_char_next;
-                    token += utf_char_next_next;
-
-                    bpe_offsets.emplace_back(unicode_cpts_from_utf8(token).size());
-                    token = "";
-                    i += 2;
-                    continue;
                 }
             }
 
-            if (!split_condition && !collecting) {
-                if (unicode_cpt_type(utf_char) == CODEPOINT_TYPE_LETTER || (token.empty() && utf_char == " " && unicode_cpt_type(utf_char_next) == CODEPOINT_TYPE_LETTER)) {
-                    collecting_letter = true;
-                    collecting = true;
-                }
-                else if (unicode_cpt_type(utf_char) == CODEPOINT_TYPE_DIGIT || (token.empty() && utf_char == " " && unicode_cpt_type(utf_char_next) == CODEPOINT_TYPE_DIGIT)) {
-                    collecting_numeric = true;
-                    collecting = true;
-                }
-                else if (
-                    ((unicode_cpt_type(utf_char) != CODEPOINT_TYPE_LETTER && unicode_cpt_type(utf_char) != CODEPOINT_TYPE_DIGIT) && (unicode_cpt_type(utf_char) != CODEPOINT_TYPE_WHITESPACE)) ||
-                    (token.empty() && utf_char == " " && unicode_cpt_type(utf_char_next) != CODEPOINT_TYPE_LETTER && unicode_cpt_type(utf_char_next) != CODEPOINT_TYPE_DIGIT && unicode_cpt_type(utf_char_next) != CODEPOINT_TYPE_WHITESPACE)
-                    ) {
-                    collecting_special = true;
-                    collecting = true;
-                }
-                else if (unicode_cpt_type(utf_char) == CODEPOINT_TYPE_WHITESPACE && unicode_cpt_type(utf_char_next) == CODEPOINT_TYPE_WHITESPACE) {
-                    collecting_whitespace_lookahead = true;
-                    collecting = true;
-                }
-                else if (unicode_cpt_type(utf_char) == CODEPOINT_TYPE_WHITESPACE) {
-                    split_condition = true;
-                }
+            int cpt2_type = (cpt == ' ' ? _get_cpt_type(pos+1) : cpt_type);
+            // regex: <space>?\p{L}+
+            if (cpt2_type == CODEPOINT_TYPE_LETTER) {
+                pos += (cpt == ' ');
+                while(cpt2_type == CODEPOINT_TYPE_LETTER)
+                    cpt2_type = _get_cpt_type(++pos);
+                _add_token(pos);
+                continue;
             }
-            else if (!split_condition && collecting) {
-                if (collecting_letter && unicode_cpt_type(utf_char) != CODEPOINT_TYPE_LETTER) {
-                    split_condition = true;
-                }
-                else if (collecting_numeric && unicode_cpt_type(utf_char) != CODEPOINT_TYPE_DIGIT) {
-                    split_condition = true;
-                }
-                else if (collecting_special && (unicode_cpt_type(utf_char) == CODEPOINT_TYPE_LETTER || unicode_cpt_type(utf_char) == CODEPOINT_TYPE_DIGIT || unicode_cpt_type(utf_char) == CODEPOINT_TYPE_WHITESPACE)) {
-                    split_condition = true;
-                }
-                else if (collecting_whitespace_lookahead && (unicode_cpt_type(utf_char_next) == CODEPOINT_TYPE_LETTER || unicode_cpt_type(utf_char_next) == CODEPOINT_TYPE_DIGIT)) {
-                    split_condition = true;
-                }
+            // regex: <space>?\p{N}+
+            if (cpt2_type == CODEPOINT_TYPE_DIGIT) {
+                pos += (cpt == ' ');
+                while(cpt2_type == CODEPOINT_TYPE_DIGIT)
+                    cpt2_type = _get_cpt_type(++pos);
+                _add_token(pos);
+                continue;
+            }
+            // regex: <space>?[^\s\p{L}\p{N}]+
+            if (cpt2_type != CODEPOINT_TYPE_WHITESPACE && cpt2_type != CODEPOINT_TYPE_LETTER && cpt2_type != CODEPOINT_TYPE_DIGIT && cpt2_type != CODEPOINT_TYPE_UNIDENTIFIED) {
+                pos += (cpt == ' ');
+                while(cpt2_type != CODEPOINT_TYPE_WHITESPACE && cpt2_type != CODEPOINT_TYPE_LETTER && cpt2_type != CODEPOINT_TYPE_DIGIT && cpt2_type != CODEPOINT_TYPE_UNIDENTIFIED)
+                    cpt2_type = _get_cpt_type(++pos);
+                _add_token(pos);
+                continue;
             }
 
-            if (utf_char_next == "") {
-                split_condition = true; // final
-                token += utf_char;
+            size_t num_whitespaces = 0;
+            while (_get_cpt_type(pos+num_whitespaces) == CODEPOINT_TYPE_WHITESPACE) {
+                num_whitespaces++;
+                }
+
+            // regex: \s+(?!\S)
+            if(num_whitespaces > 1 && _get_cpt(pos+num_whitespaces) != 0) {
+                pos += num_whitespaces - 1;
+                _add_token(pos);
+                continue;
             }
 
-            if (split_condition) {
-                if (token.size()) {
-                    bpe_offsets.emplace_back(unicode_cpts_from_utf8(token).size());
-                }
-                token = utf_char;
-                collecting = false;
-                collecting_letter = false;
-                collecting_numeric = false;
-                collecting_special = false;
-                collecting_whitespace_lookahead = false;
-            }
-            else {
-                token += utf_char;
+            // regex: \s+
+            if(num_whitespaces > 0) {
+                pos += num_whitespaces;
+                _add_token(pos);
+                continue;
             }
+
+            // no matches
+            _add_token(++pos);
         }
-
-        start += offset;
     }
 
     return bpe_offsets;