X-Git-Url: http://nitlanguage.org

diff --git a/lib/core/text/flat.nit b/lib/core/text/flat.nit
index c3332d0..2c29d90 100644
--- a/lib/core/text/flat.nit
+++ b/lib/core/text/flat.nit
@@ -36,31 +36,49 @@ end
 
 redef class FlatText
 
-	# First byte of the NativeString
+	# First byte of the CString
 	protected fun first_byte: Int do return 0
 
-	# Last byte of the NativeString
-	protected fun last_byte: Int do return _bytelen - 1
+	# Last byte of the CString
+	protected fun last_byte: Int do return first_byte + _byte_length - 1
 
 	# Cache of the latest position (char) explored in the string
 	var position: Int = 0
 
-	# Cached position (bytes) in the NativeString underlying the String
+	# Cached position (bytes) in the CString underlying the String
 	var bytepos: Int = 0
 
 	# Index of the character `index` in `_items`
 	fun char_to_byte_index(index: Int): Int do
-		var ln = length
-		assert index >= 0
-		assert index < ln
+		var dpos = index - _position
+		var b = _bytepos
+		var its = _items
 
+		if dpos == 1 then
+			if its[b] & 0x80u8 == 0x00u8 then
+				b += 1
+			else
+				b += its.length_of_char_at(b)
+			end
+			_bytepos = b
+			_position = index
+			return b
+		end
+		if dpos == -1 then
+			b = its.find_beginning_of_char_at(b - 1)
+			_bytepos = b
+			_position = index
+			return b
+		end
+		if dpos == 0 then return b
+
+		var ln = _length
 		var pos = _position
 		# Find best insertion point
 		var delta_begin = index
 		var delta_end = (ln - 1) - index
 		var delta_cache = (pos - index).abs
 		var min = delta_begin
-		var its = _items
 
 		if delta_cache < min then min = delta_cache
 		if delta_end < min then min = delta_end
@@ -68,15 +86,15 @@ redef class FlatText
 		var ns_i: Int
 		var my_i: Int
 
-		if min == delta_begin then
-			ns_i = first_byte
-			my_i = 0
-		else if min == delta_cache then
+		if min == delta_cache then
 			ns_i = _bytepos
 			my_i = pos
+		else if min == delta_begin then
+			ns_i = first_byte
+			my_i = 0
 		else
 			ns_i = its.find_beginning_of_char_at(last_byte)
-			my_i = length - 1
+			my_i = _length - 1
 		end
 
 		ns_i = its.char_to_byte_index_cached(index, my_i, ns_i)
@@ -120,8 +138,8 @@ redef class FlatText
 		var its = _items
 		var max = last_byte
 		var pos = first_byte
-		var nlen = extra + _bytelen
-		var nits = new NativeString(nlen)
+		var nlen = extra + _byte_length
+		var nits = new CString(nlen)
 		var outpos = 0
 		while pos <= max do
 			var c = its[pos]
@@ -181,7 +199,7 @@ redef class FlatText
 			end
 			pos += 1
 		end
-		var s = new FlatString.with_infos(nits, nlen, 0, nlen - 1)
+		var s = new FlatString.with_infos(nits, nlen, 0)
 		return s
 	end
 
@@ -207,6 +225,22 @@ redef class FlatText
 				req_esc += 1
 			else if c == 0x5Cu8 then
 				req_esc += 1
+			else if c == 0x3Fu8 then
+				var j = pos + 1
+				if j < length then
+					var next = its[j]
+					# We ignore `??'` because it will be escaped as `??\'`.
+					if
+						next == 0x21u8 or
+						next == 0x28u8 or
+						next == 0x29u8 or
+						next == 0x2Du8 or
+						next == 0x2Fu8 or
+						next == 0x3Cu8 or
+						next == 0x3Du8 or
+						next == 0x3Eu8
+					then req_esc += 1
+				end
 			else if c < 32u8 then
 				req_esc += 3
 			end
@@ -220,8 +254,8 @@ redef class FlatText
 		if ln_extra == 0 then return self.to_s
 		var its = _items
 		var max = last_byte
-		var nlen = _bytelen + ln_extra
-		var nns = new NativeString(nlen)
+		var nlen = _byte_length + ln_extra
+		var nns = new CString(nlen)
 		var pos = first_byte
 		var opos = 0
 		while pos <= max do
@@ -262,6 +296,27 @@ redef class FlatText
 				nns[opos] = 0x5Cu8
 				nns[opos + 1] = 0x5Cu8
 				opos += 2
+			else if c == 0x3Fu8 then
+				var j = pos + 1
+				if j < length then
+					var next = its[j]
+					# We ignore `??'` because it will be escaped as `??\'`.
+					if
+						next == 0x21u8 or
+						next == 0x28u8 or
+						next == 0x29u8 or
+						next == 0x2Du8 or
+						next == 0x2Fu8 or
+						next == 0x3Cu8 or
+						next == 0x3Du8 or
+						next == 0x3Eu8
+					then
+						nns[opos] = 0x5Cu8
+						opos += 1
+					end
+				end
+				nns[opos] = 0x3Fu8
+				opos += 1
 			else if c < 32u8 then
 				nns[opos] = 0x5Cu8
 				nns[opos + 1] = 0x30u8
@@ -274,48 +329,118 @@ redef class FlatText
 			end
 			pos += 1
 		end
-		return nns.to_s_with_length(nlen)
+		return nns.to_s_unsafe(nlen)
 	end
 
-	redef fun [](index) do return _items.char_at(char_to_byte_index(index))
+	redef fun [](index) do
+		var len = _length
+
+		# Statistically:
+		# * ~70% want the next char
+		# * ~23% want the previous
+		# * ~7% want the same char
+		#
+		# So it makes sense to shortcut early. And early is here.
+		var dpos = index - _position
+		var b = _bytepos
+		if dpos == 1 and index < len - 1 then
+			var its = _items
+			var c = its[b]
+			if c & 0x80u8 == 0x00u8 then
+				# We want the next, and current is easy.
+				# So next is easy to find!
+				b += 1
+				_position = index
+				_bytepos = b
+				# The rest will be done by `dpos==0` bellow.
+				dpos = 0
+			end
+		else if dpos == -1 and index > 1 then
+			var its = _items
+			var c = its[b-1]
+			if c & 0x80u8 == 0x00u8 then
+				# We want the previous, and it is easy.
+				b -= 1
+				dpos = 0
+				_position = index
+				_bytepos = b
+				return c.ascii
+			end
+		end
+		if dpos == 0 then
+			# We know what we want (+0 or +1) just get it now!
+			var its = _items
+			var c = its[b]
+			if c & 0x80u8 == 0x00u8 then return c.ascii
+			return items.char_at(b)
+		end
+
+		assert index >= 0 and index < len
+		return fetch_char_at(index)
+	end
+
+	# Gets a `Char` at `index` in `self`
+	#
+	# WARNING: Use at your own risks as no bound-checking is done
+	fun fetch_char_at(index: Int): Char do
+		var i = char_to_byte_index(index)
+		var items = _items
+		var b = items[i]
+		if b & 0x80u8 == 0x00u8 then return b.ascii
+		return items.char_at(i)
+	end
+
+	# If `self` contains only digits and alpha <= 'f', return the corresponding integer.
+	#
+	#     assert "ff".to_hex == 255
+	redef fun to_hex(pos, ln) do
+		var res = 0
+		if pos == null then pos = 0
+		if ln == null then ln = length - pos
+		pos = char_to_byte_index(pos)
+		var its = _items
+		var max = pos + ln
+		for i in [pos .. max[ do
+			res <<= 4
+			res += its[i].ascii.from_hex
+		end
+		return res
+	end
+
+	redef fun copy_to_native(dst, n, src_off, dst_off) do
+		_items.copy_to(dst, n, first_byte + src_off, dst_off)
+	end
 end
 
 # Immutable strings of characters.
-class FlatString
+abstract class FlatString
 	super FlatText
 	super String
 
 	# Index at which `self` begins in `_items`, inclusively
 	redef var first_byte is noinit
 
-	# Index at which `self` ends in `_items`, inclusively
-	redef var last_byte is noinit
-
-	redef var chars = new FlatStringCharView(self) is lazy
+	redef fun chars do return new FlatStringCharView(self)
 
-	redef var bytes = new FlatStringByteView(self) is lazy
+	redef fun bytes do return new FlatStringByteView(self)
 
-	redef var length is lazy do
-		if _bytelen == 0 then return 0
-		return _items.utf8_length(_first_byte, _last_byte)
-	end
-
-	redef var to_cstring is lazy do
-		var blen = _bytelen
-		var new_items = new NativeString(blen + 1)
+	redef fun to_cstring do
+		var blen = _byte_length
+		var new_items = new CString(blen + 1)
 		_items.copy_to(new_items, blen, _first_byte, 0)
 		new_items[blen] = 0u8
 		return new_items
 	end
 
-	redef fun reversed
-	do
-		var b = new FlatBuffer.with_capacity(_bytelen + 1)
-		for i in [length - 1 .. 0].step(-1) do
-			b.add self[i]
+	redef fun reversed do
+		var b = new FlatBuffer.with_capacity(_byte_length + 1)
+		var i = _length - 1
+		while i >= 0 do
+			b.add self.fetch_char_at(i)
+			i -= 1
 		end
 		var s = b.to_s.as(FlatString)
-		s.length = self.length
+		s._length = self._length
 		return s
 	end
 
@@ -323,24 +448,40 @@ class FlatString
 
 	redef fun substring(from, count)
 	do
-		assert count >= 0
+		if count <= 0 then return ""
 
 		if from < 0 then
 			count += from
-			if count < 0 then count = 0
+			if count <= 0 then return ""
 			from = 0
 		end
 
-		if (count + from) > length then count = length - from
+		var ln = _length
+		if (count + from) > ln then count = ln - from
 		if count <= 0 then return ""
 		var end_index = from + count - 1
+		return substring_impl(from, count, end_index)
+	end
+
+	private fun substring_impl(from, count, end_index: Int): String do
+		var cache = _position
+		var dfrom = (cache - from).abs
+		var dend = (end_index - from).abs
+
+		var bytefrom: Int
+		var byteto: Int
+		if dfrom < dend then
+			bytefrom = char_to_byte_index(from)
+			byteto = char_to_byte_index(end_index)
+		else
+			byteto = char_to_byte_index(end_index)
+			bytefrom = char_to_byte_index(from)
+		end
 
-		var bytefrom = char_to_byte_index(from)
-		var byteto = char_to_byte_index(end_index)
 		var its = _items
 		byteto += its.length_of_char_at(byteto) - 1
 
-		var s = new FlatString.full(its, byteto - bytefrom + 1, bytefrom, byteto, count)
+		var s = new FlatString.full(its, byteto - bytefrom + 1, bytefrom, count)
 		return s
 	end
 
@@ -348,9 +489,9 @@ class FlatString
 
 	redef fun to_upper
 	do
-		var outstr = new FlatBuffer.with_capacity(self._bytelen + 1)
+		var outstr = new FlatBuffer.with_capacity(self._byte_length + 1)
 
-		var mylen = length
+		var mylen = _length
 		var pos = 0
 
 		while pos < mylen do
@@ -363,9 +504,9 @@ class FlatString
 
 	redef fun to_lower
 	do
-		var outstr = new FlatBuffer.with_capacity(self._bytelen + 1)
+		var outstr = new FlatBuffer.with_capacity(self._byte_length + 1)
 
-		var mylen = length
+		var mylen = _length
 		var pos = 0
 
 		while pos < mylen do
@@ -389,27 +530,21 @@ class FlatString
 	#
 	# `_items` will be used as is, without copy, to retrieve the characters of the string.
 	# Aliasing issues is the responsibility of the caller.
-	private init with_infos(items: NativeString, bytelen, from, to: Int)
+	private new with_infos(items: CString, byte_length, from: Int)
 	do
-		self._items = items
-		self._bytelen = bytelen
-		_first_byte = from
-		_last_byte = to
-		_bytepos = from
+		var len = items.utf8_length(from, byte_length)
+		if byte_length == len then return new ASCIIFlatString.full_data(items, byte_length, from, len)
+		return new UnicodeFlatString.full_data(items, byte_length, from, len)
 	end
 
 	# Low-level creation of a new string with all the data.
 	#
 	# `_items` will be used as is, without copy, to retrieve the characters of the string.
 	# Aliasing issues is the responsibility of the caller.
-	private init full(items: NativeString, bytelen, from, to, length: Int)
+	private new full(items: CString, byte_length, from, length: Int)
 	do
-		self._items = items
-		self.length = length
-		self._bytelen = bytelen
-		_first_byte = from
-		_last_byte = to
-		_bytepos = from
+		if byte_length == length then return new ASCIIFlatString.full_data(items, byte_length, from, length)
+		return new UnicodeFlatString.full_data(items, byte_length, from, length)
 	end
 
 	redef fun ==(other)
@@ -418,9 +553,9 @@ class FlatString
 
 		if self.object_id == other.object_id then return true
 
-		var my_length = _bytelen
+		var my_length = _byte_length
 
-		if other._bytelen != my_length then return false
+		if other._byte_length != my_length then return false
 
 		var my_index = _first_byte
 		var its_index = other.first_byte
@@ -448,8 +583,8 @@ class FlatString
 		var myits = _items
 		var itsits = other._items
 
-		var mbt = _bytelen
-		var obt = other.bytelen
+		var mbt = _byte_length
+		var obt = other.byte_length
 
 		var minln = if mbt < obt then mbt else obt
 		var mst = _first_byte
@@ -471,42 +606,41 @@ class FlatString
 
 	redef fun +(o) do
 		var s = o.to_s
-		var slen = s.bytelen
-		var mlen = _bytelen
+		var slen = s.byte_length
+		var mlen = _byte_length
 		var nlen = mlen + slen
 		var mits = _items
 		var mifrom = _first_byte
 		if s isa FlatText then
 			var sits = s._items
 			var sifrom = s.first_byte
-			var ns = new NativeString(nlen + 1)
+			var ns = new CString(nlen + 1)
 			mits.copy_to(ns, mlen, mifrom, 0)
 			sits.copy_to(ns, slen, sifrom, mlen)
-			return new FlatString.full(ns, nlen, 0, nlen - 1, length + o.length)
+			return new FlatString.full(ns, nlen, 0, _length + o.length)
 		else
 			abort
 		end
 	end
 
 	redef fun *(i) do
-		var mybtlen = _bytelen
-		var new_bytelen = mybtlen * i
-		var mylen = length
+		var mybtlen = _byte_length
+		var new_byte_length = mybtlen * i
+		var mylen = _length
 		var newlen = mylen * i
 		var its = _items
 		var fb = _first_byte
-		var ns = new NativeString(new_bytelen + 1)
-		ns[new_bytelen] = 0u8
+		var ns = new CString(new_byte_length + 1)
+		ns[new_byte_length] = 0u8
 		var offset = 0
 		while i > 0 do
 			its.copy_to(ns, mybtlen, fb, offset)
 			offset += mybtlen
 			i -= 1
 		end
-		return new FlatString.full(ns, new_bytelen, 0, new_bytelen - 1, newlen)
+		return new FlatString.full(ns, new_byte_length, 0, newlen)
 	end
 
-
 	redef fun hash
 	do
 		if hash_cache == null then
@@ -515,7 +649,7 @@ class FlatString
 			var i = _first_byte
 
 			var my_items = _items
-			var max = _last_byte
+			var max = last_byte
 
 			while i <= max do
 				h = (h << 5) + h + my_items[i].to_i
@@ -531,6 +665,80 @@ class FlatString
 	redef fun substrings do return new FlatSubstringsIter(self)
 end
 
+# Regular Nit UTF-8 strings
+private class UnicodeFlatString
+	super FlatString
+
+	init full_data(items: CString, byte_length, from, length: Int) do
+		self._items = items
+		self._length = length
+		self._byte_length = byte_length
+		_first_byte = from
+		_bytepos = from
+	end
+
+	redef fun substring_from(from) do
+		if from >= self._length then return empty
+		if from <= 0 then return self
+		var c = char_to_byte_index(from)
+		var st = c - _first_byte
+		var fln = byte_length - st
+		return new FlatString.full(items, fln, c, _length - from)
+	end
+end
+
+# Special cases of String where all the characters are ASCII-based
+#
+# Optimizes access operations to O(1) complexity.
+private class ASCIIFlatString
+	super FlatString
+
+	init full_data(items: CString, byte_length, from, length: Int) do
+		self._items = items
+		self._length = length
+		self._byte_length = byte_length
+		_first_byte = from
+		_bytepos = from
+	end
+
+	redef fun [](idx) do
+		assert idx < _byte_length and idx >= 0
+		return _items[idx + _first_byte].ascii
+	end
+
+	redef fun substring(from, count) do
+		var ln = _length
+		if count <= 0 then return ""
+		if (count + from) > ln then count = ln - from
+		if count <= 0 then return ""
+		if from < 0 then
+			count += from
+			if count <= 0 then return ""
+			from = 0
+		end
+		return new ASCIIFlatString.full_data(_items, count, from + _first_byte, count)
+	end
+
+	redef fun reversed do
+		var b = new FlatBuffer.with_capacity(_byte_length + 1)
+		var i = _length - 1
+		while i >= 0 do
+			b.add self[i]
+			i -= 1
+		end
+		var s = b.to_s.as(FlatString)
+		return s
+	end
+
+	redef fun char_to_byte_index(index) do return index + _first_byte
+
+	redef fun substring_impl(from, count, end_index) do
+		return new ASCIIFlatString.full_data(_items, count, from + _first_byte, count)
+	end
+
+	redef fun fetch_char_at(i) do return _items[i + _first_byte].ascii
+end
+
 private class FlatStringCharReverseIterator
 	super IndexedIterator[Char]
 
@@ -557,7 +765,7 @@ private class FlatStringCharIterator
 
 	var curr_pos: Int
 
-	init do max = target.length - 1
+	init do max = target._length - 1
 
 	redef fun is_ok do return curr_pos <= max
 
@@ -587,7 +795,7 @@ private class FlatStringByteReverseIterator
 
 	var target: FlatString
 
-	var target_items: NativeString is noautoinit
+	var target_items: CString is noautoinit
 
 	var curr_pos: Int
 
@@ -613,7 +821,7 @@ private class FlatStringByteIterator
 
 	var target: FlatString
 
-	var target_items: NativeString is noautoinit
+	var target_items: CString is noautoinit
 
 	var curr_pos: Int
 
@@ -624,7 +832,7 @@ private class FlatStringByteIterator
 		curr_pos += tgt._first_byte
 	end
 
-	redef fun is_ok do return curr_pos <= target._last_byte
+	redef fun is_ok do return curr_pos <= target.last_byte
 
 	redef fun item do return target_items[curr_pos]
 
@@ -641,12 +849,11 @@ private class FlatStringByteView
 
 	redef fun [](index)
 	do
-		# Check that the index (+ _first_byte) is not larger than _last_byte
+		# Check that the index (+ _first_byte) is not larger than last_byte
 		# In other terms, if the index is valid
-		assert index >= 0
-		var target = self.target
+		var target = _target
+		assert index >= 0 and index < target._byte_length
 		var ind = index + target._first_byte
-		assert ind <= target._last_byte
 		return target._items[ind]
 	end
 
@@ -667,46 +874,37 @@ class FlatBuffer
 	super FlatText
 	super Buffer
 
-	redef var chars: Sequence[Char] = new FlatBufferCharView(self) is lazy
+	redef fun chars do return new FlatBufferCharView(self)
 
-	redef var bytes = new FlatBufferByteView(self) is lazy
-
-	redef var length = 0
-
-	private var char_cache: Int = -1
-
-	private var byte_cache: Int = -1
+	redef fun bytes do return new FlatBufferByteView(self)
 
 	private var capacity = 0
 
-	# Real items, used as cache for when to_cstring is called
-	private var real_items: NativeString is noinit
-
 	redef fun fast_cstring do return _items.fast_cstring(0)
 
 	redef fun substrings do return new FlatSubstringsIter(self)
 
-	# Re-copies the `NativeString` into a new one and sets it as the new `Buffer`
+	# Re-copies the `CString` into a new one and sets it as the new `Buffer`
 	#
 	# This happens when an operation modifies the current `Buffer` and
 	# the Copy-On-Write flag `written` is set at true.
 	private fun reset do
-		var nns = new NativeString(capacity)
-		if _bytelen != 0 then _items.copy_to(nns, _bytelen, 0, 0)
+		var nns = new CString(capacity)
+		if _byte_length != 0 then _items.copy_to(nns, _byte_length, 0, 0)
 		_items = nns
 		written = false
 	end
 
 	# Shifts the content of the buffer by `len` bytes to the right, starting at byte `from`
 	#
-	# Internal only, does not modify _bytelen or length, this is the caller's responsability
+	# Internal only, does not modify _byte_length or length, this is the caller's responsability
 	private fun rshift_bytes(from: Int, len: Int) do
 		var oit = _items
 		var nit = _items
-		var bt = _bytelen
+		var bt = _byte_length
 		if bt + len > capacity then
 			capacity = capacity * 2 + 2
-			nit = new NativeString(capacity)
+			nit = new CString(capacity)
 			oit.copy_to(nit, 0, 0, from)
 		end
 		oit.copy_to(nit, bt - from, from, from + len)
@@ -714,18 +912,17 @@ class FlatBuffer
 
 	# Shifts the content of the buffer by `len` bytes to the left, starting at `from`
 	#
-	# Internal only, does not modify _bytelen or length, this is the caller's responsability
+	# Internal only, does not modify _byte_length or length, this is the caller's responsability
 	private fun lshift_bytes(from: Int, len: Int) do
 		var it = _items
-		it.copy_to(it, _bytelen - from, from, from - len)
+		it.copy_to(it, _byte_length - from, from, from - len)
 	end
 
 	redef fun []=(index, item)
 	do
-		assert index >= 0 and index <= length
+		assert index >= 0 and index <= _length
 		if written then reset
-		is_dirty = true
-		if index == length then
+		if index == _length then
 			add item
 			return
 		end
@@ -740,28 +937,60 @@ class FlatBuffer
 		else if size_diff < 0 then
 			lshift_bytes(ip + clen, -size_diff)
 		end
-		_bytelen += size_diff
-		bytepos += size_diff
+		_byte_length += size_diff
 		it.set_char_at(ip, item)
 	end
 
+	redef fun insert(s, pos) do
+		assert pos >= 0 and pos <= length
+		if pos == length then
+			append s
+			return
+		end
+		var slen = s.byte_length
+		enlarge(byte_length + slen)
+		var it = _items
+		var shpos = it.char_to_byte_index(pos)
+		rshift_bytes(shpos, slen)
+		s.copy_to_native(it, slen, 0, shpos)
+		length += s.length
+		byte_length += slen
+	end
+
+	redef fun insert_char(c, pos) do
+		assert pos >= 0 and pos <= length
+		if pos == length then
+			add c
+			return
+		end
+		var clen = c.u8char_len
+		enlarge(byte_length + clen)
+		var it = _items
+		var shpos = it.char_to_byte_index(pos)
+		rshift_bytes(shpos, clen)
+		it.set_char_at(shpos, c)
+		length += 1
+		byte_length += clen
+	end
+
 	redef fun add(c)
 	do
 		if written then reset
-		is_dirty = true
 		var clen = c.u8char_len
-		var bt = _bytelen
+		var bt = _byte_length
 		enlarge(bt + clen)
 		_items.set_char_at(bt, c)
-		_bytelen += clen
-		length += 1
+		_byte_length += clen
+		_length += 1
 	end
 
 	redef fun clear do
-		is_dirty = true
-		if written then reset
-		_bytelen = 0
-		length = 0
+		_byte_length = 0
+		_length = 0
+		if written then
+			_capacity = 16
+			reset
+		end
 	end
 
 	redef fun empty do return new Buffer
@@ -770,12 +999,13 @@ class FlatBuffer
 	do
 		var c = capacity
 		if cap <= c then return
-		while c <= cap do c = c * 2 + 2
+		if c <= 16 then c = 16
+		while c <= cap do c = c * 2
 		# The COW flag can be set at false here, since
 		# it does a copy of the current `Buffer`
 		written = false
-		var bln = _bytelen
-		var a = new NativeString(c+1)
+		var bln = _byte_length
+		var a = new CString(c)
 		if bln > 0 then
 			var it = _items
 			if bln > 0 then it.copy_to(a, bln, 0, 0)
@@ -787,22 +1017,18 @@ class FlatBuffer
 	redef fun to_s
 	do
 		written = true
-		var bln = _bytelen
-		if bln == 0 then _items = new NativeString(1)
-		return new FlatString.full(_items, bln, 0, bln - 1, length)
+		var bln = _byte_length
+		if bln == 0 then _items = new CString(1)
+		return new FlatString.full(_items, bln, 0, _length)
 	end
 
 	redef fun to_cstring
 	do
-		if is_dirty then
-			var bln = _bytelen
-			var new_native = new NativeString(bln + 1)
-			new_native[bln] = 0u8
-			if length > 0 then _items.copy_to(new_native, bln, 0, 0)
-			real_items = new_native
-			is_dirty = false
-		end
-		return real_items
+		var bln = _byte_length
+		var new_native = new CString(bln + 1)
+		new_native[bln] = 0u8
+		if _length > 0 then _items.copy_to(new_native, bln, 0, 0)
+		return new_native
 	end
 
 	# Create a new empty string.
@@ -815,53 +1041,47 @@ class FlatBuffer
 	#
 	# If `_items` is shared, `written` should be set to true after the creation
 	# so that a modification will do a copy-on-write.
-	private init with_infos(items: NativeString, capacity, bytelen, length: Int)
+	private init with_infos(items: CString, capacity, byte_length, length: Int)
 	do
 		self._items = items
 		self.capacity = capacity
-		self._bytelen = bytelen
-		self.length = length
+		self._byte_length = byte_length
+		self._length = length
 	end
 
 	# Create a new string copied from `s`.
 	init from(s: Text)
 	do
-		_items = new NativeString(s.bytelen)
-		if s isa FlatText then
-			_items = s._items
-		else
-			for i in substrings do i.as(FlatString)._items.copy_to(_items, i._bytelen, 0, 0)
-		end
-		_bytelen = s.bytelen
-		length = s.length
-		_capacity = _bytelen
-		written = true
+		_items = new CString(s.byte_length)
+		for i in s.substrings do i._items.copy_to(_items, i._byte_length, first_byte, 0)
+		_byte_length = s.byte_length
+		_length = s.length
+		_capacity = _byte_length
 	end
 
 	# Create a new empty string with a given capacity.
 	init with_capacity(cap: Int)
 	do
 		assert cap >= 0
-		_items = new NativeString(cap + 1)
+		_items = new CString(cap)
 		capacity = cap
-		_bytelen = 0
+		_byte_length = 0
 	end
 
 	redef fun append(s)
 	do
 		if s.is_empty then return
-		is_dirty = true
-		var sl = s.bytelen
-		var nln = _bytelen + sl
+		var sl = s.byte_length
+		var nln = _byte_length + sl
 		enlarge(nln)
 		if s isa FlatText then
-			s._items.copy_to(_items, sl, s.first_byte, _bytelen)
+			s._items.copy_to(_items, sl, s.first_byte, _byte_length)
 		else
 			for i in s.substrings do append i
 			return
 		end
-		_bytelen = nln
-		length += s.length
+		_byte_length = nln
+		_length += s.length
 	end
 
 	# Copies the content of self in `dest`
@@ -878,18 +1098,47 @@ class FlatBuffer
 	do
 		assert count >= 0
 		if from < 0 then from = 0
-		if (from + count) > length then count = length - from
+		if (from + count) > _length then count = _length - from
 		if count <= 0 then return new Buffer
 		var its = _items
 		var bytefrom = its.char_to_byte_index(from)
 		var byteto = its.char_to_byte_index(count + from - 1)
 		byteto += its.char_at(byteto).u8char_len - 1
 		var byte_length = byteto - bytefrom + 1
-		var r_items = new NativeString(byte_length)
+		var r_items = new CString(byte_length)
 		its.copy_to(r_items, byte_length, bytefrom, 0)
 		return new FlatBuffer.with_infos(r_items, byte_length, byte_length, count)
 	end
 
+	redef fun append_substring_impl(s, from, length) do
+		if length <= 0 then return
+		if not s isa FlatText then
+			super
+			return
+		end
+		var sits = s._items
+		var bytest = s.char_to_byte_index(from)
+		var bytend = s.char_to_byte_index(from + length - 1)
+		var btln = bytend - bytest + sits.char_at(bytend).u8char_len
+		enlarge(btln + _byte_length)
+		sits.copy_to(_items, btln, bytest, _byte_length)
+		_byte_length += btln
+		_length += length
+	end
+
+	redef fun remove_at(p, len) do
+		if len == null then len = 1
+		if len == 0 then return
+		var its = _items
+		var bst = char_to_byte_index(p)
+		var bend = char_to_byte_index(p + len - 1)
+		bend += its.char_at(bend).u8char_len
+		var blen = bend - bst
+		lshift_bytes(bend, bend - bst)
+		byte_length -= blen
+		length -= len
+	end
+
 	redef fun reverse
 	do
 		written = false
@@ -900,8 +1149,8 @@ class FlatBuffer
 
 	redef fun times(repeats)
 	do
-		var bln = _bytelen
-		var x = new FlatString.full(_items, bln, 0, bln - 1, length)
+		var bln = _byte_length
+		var x = new FlatString.full(_items, bln, 0, _length)
 		for i in [1 .. repeats[ do
 			append(x)
 		end
@@ -910,13 +1159,13 @@ class FlatBuffer
 	redef fun upper
 	do
 		if written then reset
-		for i in [0 .. length[ do self[i] = self[i].to_upper
+		for i in [0 .. _length[ do self[i] = self[i].to_upper
 	end
 
 	redef fun lower
 	do
 		if written then reset
-		for i in [0 .. length[ do self[i] = self[i].to_lower
+		for i in [0 .. _length[ do self[i] = self[i].to_lower
 	end
 end
 
@@ -925,7 +1174,7 @@ private class FlatBufferByteReverseIterator
 
 	var target: FlatBuffer
 
-	var target_items: NativeString is noautoinit
+	var target_items: CString is noautoinit
 
 	var curr_pos: Int
 
@@ -959,7 +1208,7 @@ private class FlatBufferByteIterator
 
 	var target: FlatBuffer
 
-	var target_items: NativeString is noautoinit
+	var target_items: CString is noautoinit
 
 	var curr_pos: Int
 
@@ -967,7 +1216,7 @@ private class FlatBufferByteIterator
 
 	redef fun index do return curr_pos
 
-	redef fun is_ok do return curr_pos < target._bytelen
+	redef fun is_ok do return curr_pos < target._byte_length
 
 	redef fun item do return target_items[curr_pos]
 
@@ -1027,7 +1276,7 @@ private class FlatBufferCharView
 	redef fun append(s)
 	do
 		var s_length = s.length
-		if target.capacity < s.length then enlarge(s_length + target.length)
+		if target.capacity < s.length then enlarge(s_length + target._length)
 		for i in s do target.add i
 	end
 
@@ -1046,7 +1295,7 @@ private class FlatBufferCharIterator
 
 	var curr_pos: Int
 
-	init do max = target.length - 1
+	init do max = target._length - 1
 
 	redef fun index do return curr_pos
 
@@ -1058,45 +1307,64 @@ private class FlatBufferCharIterator
 
 end
 
-redef class NativeString
+redef class CString
 	redef fun to_s
 	do
 		return to_s_with_length(cstring_length)
 	end
 
-	# Returns `self` as a String of `length`.
-	redef fun to_s_with_length(length): FlatString
+	redef fun to_s_with_length(length)
 	do
 		assert length >= 0
 		return clean_utf8(length)
 	end
 
-	redef fun to_s_full(bytelen, unilen) do
-		return new FlatString.full(self, bytelen, 0, bytelen - 1, unilen)
+	redef fun to_s_full(byte_length, unilen) do
+		return new FlatString.full(self, byte_length, 0, unilen)
 	end
 
-	# Returns `self` as a new String.
-	redef fun to_s_with_copy: FlatString
+	redef fun to_s_unsafe(len) do
+		if len == null then len = cstring_length
+		return new FlatString.with_infos(self, len, 0)
+	end
+
+	redef fun to_s_with_copy do return to_s_with_copy_and_length(cstring_length)
+
+	# Get a `String` from `length` bytes at `self` copied into Nit memory
+	fun to_s_with_copy_and_length(length: Int): String
 	do
-		var length = cstring_length
 		var r = clean_utf8(length)
 		if r.items != self then return r
-		var new_self = new NativeString(length + 1)
+		var new_self = new CString(length + 1)
 		copy_to(new_self, length, 0, 0)
-		var str = new FlatString.with_infos(new_self, length, 0, length - 1)
+		var str = new FlatString.with_infos(new_self, length, 0)
 		new_self[length] = 0u8
-		str.to_cstring = new_self
 		return str
 	end
 
-	# Cleans a NativeString if necessary
+	# Cleans a CString if necessary
 	fun clean_utf8(len: Int): FlatString do
 		var replacements: nullable Array[Int] = null
 		var end_length = len
 		var pos = 0
 		var chr_ln = 0
-		while pos < len do
+		var rem = len
+		while rem > 0 do
+			while rem >= 4 do
+				var i = fetch_4_chars(pos)
+				if i & 0x80808080 != 0 then break
+				pos += 4
+				chr_ln += 4
+				rem -= 4
+			end
+			if rem == 0 then break
 			var b = self[pos]
+			if b & 0x80u8 == 0x00u8 then
+				pos += 1
+				chr_ln += 1
+				rem -= 1
+				continue
+			end
 			var nxst = length_of_char_at(pos)
 			var ok_st: Bool
 			if nxst == 1 then
@@ -1113,6 +1381,7 @@ redef class NativeString
 				replacements.add pos
 				end_length += 2
 				pos += 1
+				rem -= 1
 				chr_ln += 1
 				continue
 			end
@@ -1135,14 +1404,17 @@ redef class NativeString
 				end_length += 2
 				pos += 1
 				chr_ln += 1
+				rem -= 1
 				continue
 			end
-			pos += c.u8char_len
+			var clen = c.u8char_len
+			pos += clen
+			rem -= clen
 			chr_ln += 1
 		end
 		var ret = self
 		if end_length != len then
-			ret = new NativeString(end_length)
+			ret = new CString(end_length)
 			var old_repl = 0
 			var off = 0
 			var repls = replacements.as(not null)
@@ -1161,51 +1433,36 @@ redef class NativeString
 			end
 			copy_to(ret, len - old_repl, old_repl, off)
 		end
-		return new FlatString.full(ret, end_length, 0, end_length - 1, chr_ln)
+		return new FlatString.full(ret, end_length, 0, chr_ln)
 	end
 
 	# Sets the next bytes at position `pos` to the value of `c`, encoded in UTF-8
 	#
 	# Very unsafe, make sure to have room for this char prior to calling this function.
 	private fun set_char_at(pos: Int, c: Char) do
+		var cp = c.code_point
+		if cp < 128 then
+			self[pos] = cp.to_b
+			return
+		end
 		var ln = c.u8char_len
-		native_set_char(pos, c, ln)
-	end
-
-	private fun native_set_char(pos: Int, c: Char, ln: Int) `{
-		char* dst = self + pos;
-		switch(ln){
-			case 1:
-				dst[0] = c;
-				break;
-			case 2:
-				dst[0] = 0xC0 | ((c & 0x7C0) >> 6);
-				dst[1] = 0x80 | (c & 0x3F);
-				break;
-			case 3:
-				dst[0] = 0xE0 | ((c & 0xF000) >> 12);
-				dst[1] = 0x80 | ((c & 0xFC0) >> 6);
-				dst[2] = 0x80 | (c & 0x3F);
-				break;
-			case 4:
-				dst[0] = 0xF0 | ((c & 0x1C0000) >> 18);
-				dst[1] = 0x80 | ((c & 0x3F000) >> 12);
-				dst[2] = 0x80 | ((c & 0xFC0) >> 6);
-				dst[3] = 0x80 | (c & 0x3F);
-				break;
-		}
-	`}
+		if ln == 2 then
+			self[pos] = (0xC0 | ((cp & 0x7C0) >> 6)).to_b
+			self[pos + 1] = (0x80 | (cp & 0x3F)).to_b
+		else if ln == 3 then
+			self[pos] = (0xE0 | ((cp & 0xF000) >> 12)).to_b
+			self[pos + 1] = (0x80 | ((cp & 0xFC0) >> 6)).to_b
+			self[pos + 2] = (0x80 | (cp & 0x3F)).to_b
+		else if ln == 4 then
+			self[pos] = (0xF0 | ((cp & 0x1C0000) >> 18)).to_b
+			self[pos + 1] = (0x80 | ((cp & 0x3F000) >> 12)).to_b
+			self[pos + 2] = (0x80 | ((cp & 0xFC0) >> 6)).to_b
+			self[pos + 3] = (0x80 | (cp & 0x3F)).to_b
+		end
+	end
 end
 
 redef class Int
-	redef fun to_base(base, signed)
-	do
-		var l = digit_count(base)
-		var s = new FlatBuffer.from(" " * l)
-		fill_buffer(s, base, signed)
-		return s.to_s
-	end
-
 	# return displayable int in base 10 and signed
 	#
 	#     assert 1.to_s            == "1"
@@ -1216,10 +1473,10 @@ redef class Int
 		if self == 1 then return "1"
 
 		var nslen = int_to_s_len
-		var ns = new NativeString(nslen + 1)
+		var ns = new CString(nslen + 1)
 		ns[nslen] = 0u8
 		native_int_to_s(ns, nslen + 1)
-		return new FlatString.full(ns, nslen, 0, nslen - 1, nslen)
+		return new FlatString.full(ns, nslen, 0, nslen)
 	end
 end
 
@@ -1228,7 +1485,7 @@ redef class Array[E]
 	# Fast implementation
 	redef fun plain_to_s
 	do
-		var l = length
+		var l = _length
 		if l == 0 then return ""
 		var its = _items.as(not null)
 		var first = its[0]
@@ -1244,32 +1501,32 @@ redef class Array[E]
 				continue
 			end
 			var tmp = itsi.to_s
-			sl += tmp.bytelen
+			sl += tmp.byte_length
 			na[mypos] = tmp
 			i += 1
 			mypos += 1
 		end
-		var ns = new NativeString(sl + 1)
+		var ns = new CString(sl + 1)
 		ns[sl] = 0u8
 		i = 0
 		var off = 0
 		while i < mypos do
 			var tmp = na[i]
 			if tmp isa FlatString then
-				var tpl = tmp._bytelen
+				var tpl = tmp._byte_length
 				tmp._items.copy_to(ns, tpl, tmp._first_byte, off)
 				off += tpl
 			else
 				for j in tmp.substrings do
 					var s = j.as(FlatString)
-					var slen = s._bytelen
+					var slen = s._byte_length
 					s._items.copy_to(ns, slen, s._first_byte, off)
 					off += slen
 				end
 			end
 			i += 1
 		end
-		return new FlatString.with_infos(ns, sl, 0, sl - 1)
+		return new FlatString.with_infos(ns, sl, 0)
 	end
 end
 
@@ -1282,31 +1539,31 @@ redef class NativeArray[E]
 		var sl = 0
 		var mypos = 0
 		while i < l do
-			sl += na[i].bytelen
+			sl += na[i].byte_length
 			i += 1
 			mypos += 1
 		end
-		var ns = new NativeString(sl + 1)
+		var ns = new CString(sl + 1)
 		ns[sl] = 0u8
 		i = 0
 		var off = 0
 		while i < mypos do
 			var tmp = na[i]
 			if tmp isa FlatString then
-				var tpl = tmp._bytelen
+				var tpl = tmp._byte_length
 				tmp._items.copy_to(ns, tpl, tmp._first_byte, off)
 				off += tpl
 			else
 				for j in tmp.substrings do
 					var s = j.as(FlatString)
-					var slen = s._bytelen
+					var slen = s._byte_length
 					s._items.copy_to(ns, slen, s._first_byte, off)
 					off += slen
 				end
 			end
 			i += 1
 		end
-		return new FlatString.with_infos(ns, sl, 0, sl - 1)
+		return new FlatString.with_infos(ns, sl, 0)
 	end
 end