diff --git a/tests/data/corpora/sentencise/text.txt b/tests/data/corpora/sentencise/text.txt
new file mode 100644
index 0000000..c20792d
--- /dev/null
+++ b/tests/data/corpora/sentencise/text.txt
@@ -0,0 +1,6 @@
+3.14 is a number, not some B.S. You know M.D. Bob is my friend.
+I've got my Ph.D. in 2014. I have Ph.D. I got it in 2014.
+
+А по-русски слабо? Что делать с гос. служащими?
+富士山が見える。こんにちは
+    
\ No newline at end of file
diff --git a/vecto/_version.py b/vecto/_version.py
index 8cc0063..246cf2a 100644
--- a/vecto/_version.py
+++ b/vecto/_version.py
@@ -1,3 +1,3 @@
 """Version of vecto package."""
 
-VERSION = "0.2.16"
+VERSION = "0.2.21"
diff --git a/vecto/corpus/corpus.py b/vecto/corpus/corpus.py
index eaf2cbc..7a78156 100644
--- a/vecto/corpus/corpus.py
+++ b/vecto/corpus/corpus.py
@@ -6,8 +6,8 @@
 from vecto.utils.data import get_uncompressed_size
 from vecto.utils.metadata import WithMetaData
 
-from .iterators import (DirIterator, FileIterator, FileLineIterator,
-                        LoopedLineIterator, SequenceIterator,
+from .iterators import (CharIterator, DirIterator, FileIterator,
+                        FileLineIterator, LoopedLineIterator, SequenceIterator,
                         SlidingWindowIterator, TokenIterator,
                         TokenizedSequenceIterator, ViewLineIterator)
 from .tokenization import (DEFAULT_JAP_TOKENIZER, DEFAULT_SENT_TOKENIZER,
@@ -51,7 +51,7 @@ def get_token_iterator(self, tokenizer=None, verbose=False):
         return TokenIterator(self.get_sentence_iterator(tokenizer, verbose))
 
     def get_character_iterator(self, verbose=False):
-        return TokenIterator(self.get_line_iterator(verbose))
+        return CharIterator(self.get_line_iterator(verbose))
 
     def get_sentence_iterator(self, tokenizer=None, verbose=False):
         if tokenizer is None:
@@ -68,10 +68,12 @@ def get_sequence_iterator(self, sequence_length, tokenizer):
                                 sequence_length=sequence_length,
                                 tokenizer=tokenizer)
 
-    def get_looped_sequence_iterator(self, sequence_length, tokenizer, rank, size):
+    def get_looped_sequence_iterator(self, sequence_length, tokenizer, rank, size, min_length=0, reset_on_new_line=False):
         return SequenceIterator(self.get_looped_line_iterator(rank, size),
                                 sequence_length=sequence_length,
-                                tokenizer=tokenizer)
+                                tokenizer=tokenizer,
+                                minimal_length=min_length,
+                                reset_on_new_line=reset_on_new_line)
 
 
 class Corpus(BaseCorpus):
diff --git a/vecto/corpus/iterators.py b/vecto/corpus/iterators.py
index 057d751..b55c4a9 100644
--- a/vecto/corpus/iterators.py
+++ b/vecto/corpus/iterators.py
@@ -35,11 +35,14 @@ def __init__(self, dirname, verbose=0):
         self.dirname = dirname
 
     def _generate_samples(self):
-        for root, _, files in os.walk(self.dirname, followlinks=True):
-            for good_fname in sorted(fnmatch.filter(files, "*")):
-                full_file_path = os.path.join(root, good_fname)
-                logger.info("processing " + full_file_path)
-                yield full_file_path
+        if os.path.isfile(self.dirname):
+            yield self.dirname
+        else:
+            for root, _, files in os.walk(self.dirname, followlinks=True):
+                for good_fname in sorted(fnmatch.filter(files, "*")):
+                    full_file_path = os.path.join(root, good_fname)
+                    logger.info("processing " + full_file_path)
+                    yield full_file_path
 
 
 class FileLineIterator(BaseIterator):
@@ -110,6 +113,7 @@ def _generate_samples(self):
         filename = self.tree[self.id_file][0]
         file_in = detect_archive_format_and_open(filename)
         seek_unicode(file_in, self.start_offset)
+        file_in.readline()
         while True:
             for line in file_in:
                 line = line.strip()
@@ -150,20 +154,26 @@ def _generate_samples(self):
 
 
 class SequenceIterator(BaseIterator):
-    def __init__(self, line_terator, sequence_length, tokenizer):
+    def __init__(self, line_terator, sequence_length, tokenizer, minimal_length=0, reset_on_new_line=False):
         super().__init__()
         self.line_iterator = line_terator
         self.sequence_length = sequence_length
         self.tokenizer = tokenizer
         self.buffer = []
+        self.minimal_length = minimal_length
+        self.reset_on_new_line = reset_on_new_line
 
     def _generate_samples(self):
         # TODO: consider removing too small chunks of sentences at the end
         # TODO: consider leveraging sentence iterator is corpus has mark-up
         for line in self.line_iterator:
             tokens = self.tokenizer(line)
+            if self.reset_on_new_line:
+                self.buffer = []
+            elif len(self.buffer) < self.minimal_length:
+                self.buffer = []
             self.buffer += tokens
-            while len(self.buffer) > self.sequence_length:
+            while len(self.buffer) > self.sequence_length - self.minimal_length:
                 s = self.buffer[: self.sequence_length]
                 self.buffer = self.buffer[self.sequence_length:]
                 yield s
@@ -184,13 +194,20 @@ def __init__(self, parent_iterator, verbose=0):
 
 
 class TokenIterator(BaseNestedIterator):
-
     def _generate_samples(self):
         for tokenized_str in self.parent_iterator:
             for token in tokenized_str:
                 yield token
 
 
+class CharIterator(BaseNestedIterator):
+    def _generate_samples(self):
+        for line in self.parent_iterator:
+            for c in line:
+                yield c
+            yield " "
+
+
 def iter_sliding_window(seq, left_ctx_size, right_ctx_size):
     for i, current in enumerate(seq):
         ctx = []
diff --git a/vecto/corpus/preprocess.py b/vecto/corpus/preprocess.py
new file mode 100644
index 0000000..530a02f
--- /dev/null
+++ b/vecto/corpus/preprocess.py
@@ -0,0 +1,142 @@
+# import spacy
+# import numpy as np
+# from nltk.tokenize import sent_tokenize
+# import nltk
+import json
+import random
+import sys
+
+from transformers import AutoTokenizer
+from vecto.corpus import Corpus
+
+
+def simple_char_iter(text):
+    for c in text:
+        yield c
+
+
+# def sentencize(text):
+    # nlp = spacy.load("en_core_web_sm")
+    # doc = nlp(text)
+    # sents = [sent.text for sent in doc.sents]
+    # return [s for s in sentence_iter(char_iter(text))]
+    # sent_detector = nltk.data.load('tokenizers/punkt/english.pickle')
+    # return sent_detector.tokenize(text)
+
+
+# TODO: ok let's do streaming sentence splitter
+# ingest character by character
+# append to sentence, unles
+other_delimiters = {"?", "!", "。"}
+
+known_abbreviations = {"md", "bs", "mr", "ms"}
+
+
+def is_abbreviation(token):
+    if "." in token:
+        return True
+    if len(token) == 1:
+        return True
+    if token.lower() in known_abbreviations:
+        return True
+    return False
+
+
+def sentence_iter(char_iter):
+    size_buffer = 10000
+    buffer = [" "] * size_buffer
+    pos = 0
+    prev_char = ""
+    prev_token = ""
+    for c in char_iter:
+        is_sentence_end = False
+        if c == " " and prev_char == ".":
+            # print(prev_token)
+            if not is_abbreviation(prev_token[:-1]):
+                is_sentence_end = True
+        if prev_char in other_delimiters and c != "\"":
+            is_sentence_end = True
+            #buffer[pos] = c
+            #pos += 1
+        if is_sentence_end:
+            if pos > 0:
+                yield "".join(buffer[: pos]).strip()
+            buffer = [" "] * size_buffer
+            pos = 0
+            continue
+        prev_char = c
+        if pos >= len(buffer):
+            print("buffer overflow:")
+            # print("".join(buffer[:100]))
+            print("".join(buffer[-100:]))
+            pos = 0
+        buffer[pos] = c
+        prev_token += c
+        if c == " ":
+            prev_token = ""
+        pos += 1
+    if pos > 0:
+        yield "".join(buffer[: pos])
+
+
+def main():
+    # samples = []
+    # samples.append("Hey how do you do? M.D. Bob is my friend. Mr. John too.")
+    # samples.append("А по-русски слабо? Что делать с гос. служащими?")
+    # samples.append("富士山が見える。こんにちは")
+    # for s in samples:
+    #     tokenized = sentencize(s)
+    #     print(tokenized)
+    # path = "./tests/data/corpora/sentencise"
+    path = sys.argv[1]
+    # path = "/mnt/storage/Data/NLP/corpora/wiki_clean.txt"
+    # path = "/mnt/storage/Data/NLP/corpora/toronto_clean.txt"
+    # path = "./quotes/13th_Reality-1.txt"
+    name_tokenizer = "roberta-base"
+    tokenizer = AutoTokenizer.from_pretrained(name_tokenizer)
+    corpus = Corpus(path)
+    corpus.load_dir_strucute()
+    char_iter = corpus.get_character_iterator()
+    sent_iter = sentence_iter(char_iter)
+    # cnt = 0
+    sample = [tokenizer.cls_token_id]
+    max_length = 128
+    cnt = 0
+    proba_shortening = 0.1
+    with open("lines.jsonl", "w") as f_out:
+        for line in sent_iter:
+            tokens = tokenizer(line,
+                               add_special_tokens=False,
+                               return_attention_mask=False,)["input_ids"]
+            sample += tokens
+            if len(sample) > max_length - 10:
+                sample = sample[:max_length - 1]
+                min_length = 5
+                if random.random() < proba_shortening:
+                    sample = sample[: random.randint(min_length, len(sample))]
+                sample += [tokenizer.sep_token_id]
+                sample += [tokenizer.pad_token_id] * (max_length - len(sample))
+                # print(len(sample))
+                serialized = json.dumps(sample) 
+                if ":" in serialized:
+                    print(sample)
+                    print(serialized)
+                f_out.write(serialized)
+                f_out.write("\n")
+                #print(tokenizer.decode(sample))
+                #print(len(sample))
+                #print()
+                sample = [tokenizer.cls_token_id]
+            cnt += 1
+            if cnt % 10000 == 0:
+                print(cnt, "last line", len(tokens))
+            # print(tokenizer.convert_ids_to_tokens(tokens))
+            # print(line)
+            # print()
+            # if cnt > 100:
+                # break
+            # cnt += 1
+
+
+if __name__ == "__main__":
+    main()