lib: move errno and strerror to legacy FFI
[nit.git] / lib / standard / string.nit
index 5d158b5..8db6a4e 100644 (file)
@@ -15,7 +15,8 @@
 module string
 
 import math
-intrude import collection # FIXME should be collection::array
+import collection
+intrude import collection::array
 
 `{
 #include <stdio.h>
@@ -29,7 +30,6 @@ intrude import collection # FIXME should be collection::array
 # High-level abstraction for all text representations
 abstract class Text
        super Comparable
-       super StringCapable
 
        redef type OTHER: Text
 
@@ -156,13 +156,6 @@ abstract class Text
                return self.chars.iterator
        end
 
-       # Is 'c' contained in self ?
-       #
-       # DEPRECATED : Use self.chars.has instead
-       fun has(c: Char): Bool
-       do
-               return self.chars.has(c)
-       end
 
        # Gets an Array containing the chars of self
        #
@@ -178,7 +171,7 @@ abstract class Text
        # As with substring, a `from` index < 0 will be replaced by 0
        fun substring_from(from: Int): SELFTYPE
        do
-               if from > self.length then return empty
+               if from >= self.length then return empty
                if from < 0 then from = 0
                return substring(from, length - from)
        end
@@ -187,8 +180,25 @@ abstract class Text
        #
        #     assert "abcd".has_substring("bc",1)            ==  true
        #     assert "abcd".has_substring("bc",2)            ==  false
+       #
+       # Returns true iff all characters of `str` are presents
+       # at the expected index in `self.`
+       # The first character of `str` being at `pos`, the second
+       # character being at `pos+1` and so on...
+       #
+       # This means that all characters of `str` need to be inside `self`.
+       #
+       #     assert "abcd".has_substring("xab", -1)         == false
+       #     assert "abcd".has_substring("cdx", 2)          == false
+       #
+       # And that the empty string is always a valid substring.
+       #
+       #     assert "abcd".has_substring("", 2)             == true
+       #     assert "abcd".has_substring("", 200)           == true
        fun has_substring(str: String, pos: Int): Bool
        do
+               if str.is_empty then return true
+               if pos < 0 or pos + str.length > length then return false
                var myiter = self.chars.iterator_from(pos)
                var itsiter = str.chars.iterator
                while myiter.is_ok and itsiter.is_ok do
@@ -247,8 +257,8 @@ abstract class Text
                var i = 0
                var neg = false
 
-               for c in self.chars
-               do
+               for j in [0..length[ do
+                       var c = chars[j]
                        var v = c.to_i
                        if v > base then
                                if neg then
@@ -278,12 +288,10 @@ abstract class Text
        fun is_numeric: Bool
        do
                var has_point_or_comma = false
-               for i in self.chars
-               do
-                       if not i.is_numeric
-                       then
-                               if (i == '.' or i == ',') and not has_point_or_comma
-                               then
+               for i in [0..length[ do
+                       var c = chars[i]
+                       if not c.is_numeric then
+                               if (c == '.' or c == ',') and not has_point_or_comma then
                                        has_point_or_comma = true
                                else
                                        return false
@@ -293,6 +301,22 @@ abstract class Text
                return true
        end
 
+       # Returns `true` if the string contains only Hex chars
+       #
+       #     assert "048bf".is_hex  == true
+       #     assert "ABCDEF".is_hex  == true
+       #     assert "0G".is_hex == false
+       fun is_hex: Bool
+       do
+               for i in [0..length[ do
+                       var c = chars[i]
+                       if not (c >= 'a' and c <= 'f') and
+                          not (c >= 'A' and c <= 'F') and
+                          not (c >= '0' and c <= '9') then return false
+               end
+               return true
+       end
+
        # Are all letters in `self` upper-case ?
        #
        #     assert "HELLO WORLD".is_upper == true
@@ -301,7 +325,8 @@ abstract class Text
        #     assert "Hello World".is_upper == false
        fun is_upper: Bool
        do
-               for char in self.chars do 
+               for i in [0..length[ do
+                       var char = chars[i]
                        if char.is_lower then return false
                end
                return true
@@ -314,7 +339,8 @@ abstract class Text
        #     assert "Hello World".is_lower == false
        fun is_lower: Bool
        do
-               for char in self.chars do 
+               for i in [0..length[ do
+                       var char = chars[i]
                        if char.is_upper then return false
                end
                return true
@@ -324,12 +350,12 @@ abstract class Text
        #
        #     assert " \n\thello \n\t".l_trim == "hello \n\t"
        #
-       # A whitespace is defined as any character which ascii value is less than or equal to 32
+       # `Char::is_whitespace` determines what is a whitespace.
        fun l_trim: SELFTYPE
        do
                var iter = self.chars.iterator
                while iter.is_ok do
-                       if iter.item.ascii > 32 then break
+                       if not iter.item.is_whitespace then break
                        iter.next
                end
                if iter.index == length then return self.empty
@@ -340,31 +366,138 @@ abstract class Text
        #
        #     assert " \n\thello \n\t".r_trim == " \n\thello"
        #
-       # A whitespace is defined as any character which ascii value is less than or equal to 32
+       # `Char::is_whitespace` determines what is a whitespace.
        fun r_trim: SELFTYPE
        do
                var iter = self.chars.reverse_iterator
                while iter.is_ok do
-                       if iter.item.ascii > 32 then break
+                       if not iter.item.is_whitespace then break
                        iter.next
                end
-               if iter.index == length then return self.empty
+               if iter.index < 0 then return self.empty
                return self.substring(0, iter.index + 1)
        end
 
        # Trims trailing and preceding white spaces
-       # A whitespace is defined as any character which ascii value is less than or equal to 32
        #
        #     assert "  Hello  World !  ".trim   == "Hello  World !"
        #     assert "\na\nb\tc\t".trim          == "a\nb\tc"
+       #
+       # `Char::is_whitespace` determines what is a whitespace.
        fun trim: SELFTYPE do return (self.l_trim).r_trim
 
-       # Mangle a string to be a unique string only made of alphanumeric characters
+       # Is the string non-empty but only made of whitespaces?
+       #
+       #    assert " \n\t ".is_whitespace    == true
+       #    assert "  hello  ".is_whitespace == false
+       #    assert "".is_whitespace          == false
+       #
+       # `Char::is_whitespace` determines what is a whitespace.
+       fun is_whitespace: Bool
+       do
+               if is_empty then return false
+               for c in self.chars do
+                       if not c.is_whitespace then return false
+               end
+               return true
+       end
+
+       # Returns `self` removed from its last line terminator (if any).
+       #
+       #    assert "Hello\n".chomp == "Hello"
+       #    assert "Hello".chomp   == "Hello"
+       #
+       #    assert "\n".chomp == ""
+       #    assert "".chomp   == ""
+       #
+       # Line terminators are `"\n"`, `"\r\n"` and `"\r"`.
+       # A single line terminator, the last one, is removed.
+       #
+       #    assert "\r\n".chomp     == ""
+       #    assert "\r\n\n".chomp   == "\r\n"
+       #    assert "\r\n\r\n".chomp == "\r\n"
+       #    assert "\r\n\r".chomp   == "\r\n"
+       #
+       # Note: unlike with most IO methods like `Reader::read_line`,
+       # a single `\r` is considered here to be a line terminator and will be removed.
+       fun chomp: SELFTYPE
+       do
+               var len = length
+               if len == 0 then return self
+               var l = self.chars.last
+               if l == '\r' then
+                       return substring(0, len-1)
+               else if l != '\n' then
+                       return self
+               else if len > 1 and self.chars[len-2] == '\r' then
+                       return substring(0, len-2)
+               else
+                       return substring(0, len-1)
+               end
+       end
+
+       # Justify a self in a space of `length`
+       #
+       # `left` is the space ratio on the left side.
+       # * 0.0 for left-justified (no space at the left)
+       # * 1.0 for right-justified (all spaces at the left)
+       # * 0.5 for centered (half the spaces at the left)
+       #
+       # Examples
+       #
+       #     assert "hello".justify(10, 0.0)  == "hello     "
+       #     assert "hello".justify(10, 1.0)  == "     hello"
+       #     assert "hello".justify(10, 0.5)  == "  hello   "
+       #
+       # If `length` is not enough, `self` is returned as is.
+       #
+       #     assert "hello".justify(2, 0.0)   == "hello"
+       #
+       # REQUIRE: `left >= 0.0 and left <= 1.0`
+       # ENSURE: `self.length <= length implies result.length == length`
+       # ENSURE: `self.length >= length implies result == self`
+       fun justify(length: Int, left: Float): String
+       do
+               var diff = length - self.length
+               if diff <= 0 then return to_s
+               assert left >= 0.0 and left <= 1.0
+               var before = (diff.to_f * left).to_i
+               return " " * before + self + " " * (diff-before)
+       end
+
+       # Mangle a string to be a unique string only made of alphanumeric characters and underscores.
+       #
+       # This method is injective (two different inputs never produce the same
+       # output) and the returned string always respect the following rules:
+       #
+       # * Contains only US-ASCII letters, digits and underscores.
+       # * Never starts with a digit.
+       # * Never ends with an underscore.
+       # * Never contains two contiguous underscores.
+       #
+       #     assert "42_is/The answer!".to_cmangle == "_52d2_is_47dThe_32danswer_33d"
+       #     assert "__".to_cmangle == "_95d_95d"
+       #     assert "__d".to_cmangle == "_95d_d"
+       #     assert "_d_".to_cmangle == "_d_95d"
+       #     assert "_42".to_cmangle == "_95d42"
+       #     assert "foo".to_cmangle == "foo"
+       #     assert "".to_cmangle == ""
        fun to_cmangle: String
        do
+               if is_empty then return ""
                var res = new FlatBuffer
                var underscore = false
-               for c in self.chars do
+               var start = 0
+               var c = chars[0]
+
+               if c >= '0' and c <= '9' then
+                       res.add('_')
+                       res.append(c.ascii.to_s)
+                       res.add('d')
+                       start = 1
+               end
+               for i in [start..length[ do
+                       c = chars[i]
                        if (c >= 'a' and c <= 'z') or (c >='A' and c <= 'Z') then
                                res.add(c)
                                underscore = false
@@ -387,6 +520,10 @@ abstract class Text
                                underscore = false
                        end
                end
+               if underscore then
+                       res.append('_'.ascii.to_s)
+                       res.add('d')
+               end
                return res.to_s
        end
 
@@ -394,14 +531,25 @@ abstract class Text
        #
        #     assert "abAB12<>&".escape_to_c         == "abAB12<>&"
        #     assert "\n\"'\\".escape_to_c         == "\\n\\\"\\'\\\\"
+       #
+       # Most non-printable characters (bellow ASCII 32) are escaped to an octal form `\nnn`.
+       # Three digits are always used to avoid following digits to be interpreted as an element
+       # of the octal sequence.
+       #
+       #     assert "{0.ascii}{1.ascii}{8.ascii}{31.ascii}{32.ascii}".escape_to_c == "\\000\\001\\010\\037 "
+       #
+       # The exceptions are the common `\t` and `\n`.
        fun escape_to_c: String
        do
                var b = new FlatBuffer
-               for c in self.chars do
+               for i in [0..length[ do
+                       var c = chars[i]
                        if c == '\n' then
                                b.append("\\n")
+                       else if c == '\t' then
+                               b.append("\\t")
                        else if c == '\0' then
-                               b.append("\\0")
+                               b.append("\\000")
                        else if c == '"' then
                                b.append("\\\"")
                        else if c == '\'' then
@@ -409,7 +557,17 @@ abstract class Text
                        else if c == '\\' then
                                b.append("\\\\")
                        else if c.ascii < 32 then
-                               b.append("\\{c.ascii.to_base(8, false)}")
+                               b.add('\\')
+                               var oct = c.ascii.to_base(8, false)
+                               # Force 3 octal digits since it is the
+                               # maximum allowed in the C specification
+                               if oct.length == 1 then
+                                       b.add('0')
+                                       b.add('0')
+                               else if oct.length == 2 then
+                                       b.add('0')
+                               end
+                               b.append(oct)
                        else
                                b.add(c)
                        end
@@ -438,6 +596,50 @@ abstract class Text
        #     assert "\n\"'\\\{\}".escape_to_nit      == "\\n\\\"\\'\\\\\\\{\\\}"
        fun escape_to_nit: String do return escape_more_to_c("\{\}")
 
+       # Escape to POSIX Shell (sh).
+       #
+       # Abort if the text contains a null byte.
+       #
+       #     assert "\n\"'\\\{\}0".escape_to_sh == "'\n\"'\\''\\\{\}0'"
+       fun escape_to_sh: String do
+               var b = new FlatBuffer
+               b.chars.add '\''
+               for i in [0..length[ do
+                       var c = chars[i]
+                       if c == '\'' then
+                               b.append("'\\''")
+                       else
+                               assert without_null_byte: c != '\0'
+                               b.add(c)
+                       end
+               end
+               b.chars.add '\''
+               return b.to_s
+       end
+
+       # Escape to include in a Makefile
+       #
+       # Unfortunately, some characters are not escapable in Makefile.
+       # These characters are `;`, `|`, `\`, and the non-printable ones.
+       # They will be rendered as `"?{hex}"`.
+       fun escape_to_mk: String do
+               var b = new FlatBuffer
+               for i in [0..length[ do
+                       var c = chars[i]
+                       if c == '$' then
+                               b.append("$$")
+                       else if c == ':' or c == ' ' or c == '#' then
+                               b.add('\\')
+                               b.add(c)
+                       else if c.ascii < 32 or c == ';' or c == '|' or c == '\\' or c == '=' then
+                               b.append("?{c.ascii.to_base(16, false)}")
+                       else
+                               b.add(c)
+                       end
+               end
+               return b.to_s
+       end
+
        # Return a string where Nit escape sequences are transformed.
        #
        #     var s = "\\n"
@@ -449,7 +651,8 @@ abstract class Text
        do
                var res = new FlatBuffer.with_capacity(self.length)
                var was_slash = false
-               for c in chars do
+               for i in [0..length[ do
+                       var c = chars[i]
                        if not was_slash then
                                if c == '\\' then
                                        was_slash = true
@@ -474,6 +677,101 @@ abstract class Text
                return res.to_s
        end
 
+       # Encode `self` to percent (or URL) encoding
+       #
+       #     assert "aBc09-._~".to_percent_encoding == "aBc09-._~"
+       #     assert "%()< >".to_percent_encoding == "%25%28%29%3c%20%3e"
+       #     assert ".com/post?e=asdf&f=123".to_percent_encoding == ".com%2fpost%3fe%3dasdf%26f%3d123"
+       fun to_percent_encoding: String
+       do
+               var buf = new FlatBuffer
+
+               for i in [0..length[ do
+                       var c = chars[i]
+                       if (c >= '0' and c <= '9') or
+                          (c >= 'a' and c <= 'z') or
+                          (c >= 'A' and c <= 'Z') or
+                          c == '-' or c == '.' or
+                          c == '_' or c == '~'
+                       then
+                               buf.add c
+                       else buf.append "%{c.ascii.to_hex}"
+               end
+
+               return buf.to_s
+       end
+
+       # Decode `self` from percent (or URL) encoding to a clear string
+       #
+       # Replace invalid use of '%' with '?'.
+       #
+       #     assert "aBc09-._~".from_percent_encoding == "aBc09-._~"
+       #     assert "%25%28%29%3c%20%3e".from_percent_encoding == "%()< >"
+       #     assert ".com%2fpost%3fe%3dasdf%26f%3d123".from_percent_encoding == ".com/post?e=asdf&f=123"
+       #     assert "%25%28%29%3C%20%3E".from_percent_encoding == "%()< >"
+       #     assert "incomplete %".from_percent_encoding == "incomplete ?"
+       #     assert "invalid % usage".from_percent_encoding == "invalid ? usage"
+       fun from_percent_encoding: String
+       do
+               var buf = new FlatBuffer
+
+               var i = 0
+               while i < length do
+                       var c = chars[i]
+                       if c == '%' then
+                               if i + 2 >= length then
+                                       # What follows % has been cut off
+                                       buf.add '?'
+                               else
+                                       i += 1
+                                       var hex_s = substring(i, 2)
+                                       if hex_s.is_hex then
+                                               var hex_i = hex_s.to_hex
+                                               buf.add hex_i.ascii
+                                               i += 1
+                                       else
+                                               # What follows a % is not Hex
+                                               buf.add '?'
+                                               i -= 1
+                                       end
+                               end
+                       else buf.add c
+
+                       i += 1
+               end
+
+               return buf.to_s
+       end
+
+       # Escape the characters `<`, `>`, `&`, `"`, `'` and `/` as HTML/XML entity references.
+       #
+       #     assert "a&b-<>\"x\"/'".html_escape      ==  "a&amp;b-&lt;&gt;&#34;x&#34;&#47;&#39;"
+       #
+       # SEE: <https://www.owasp.org/index.php/XSS_%28Cross_Site_Scripting%29_Prevention_Cheat_Sheet#RULE_.231_-_HTML_Escape_Before_Inserting_Untrusted_Data_into_HTML_Element_Content>
+       fun html_escape: String
+       do
+               var buf = new FlatBuffer
+
+               for i in [0..length[ do
+                       var c = chars[i]
+                       if c == '&' then
+                               buf.append "&amp;"
+                       else if c == '<' then
+                               buf.append "&lt;"
+                       else if c == '>' then
+                               buf.append "&gt;"
+                       else if c == '"' then
+                               buf.append "&#34;"
+                       else if c == '\'' then
+                               buf.append "&#39;"
+                       else if c == '/' then
+                               buf.append "&#47;"
+                       else buf.add c
+               end
+
+               return buf.to_s
+       end
+
        # Equality of text
        # Two pieces of text are equals if thez have the same characters in the same order.
        #
@@ -522,6 +820,14 @@ abstract class Text
                end
        end
 
+       # Escape string used in labels for graphviz
+       #
+       #   assert ">><<".escape_to_dot == "\\>\\>\\<\\<"
+       fun escape_to_dot: String
+       do
+               return escape_more_to_c("|\{\}<>")
+       end
+
        # Flat representation of self
        fun flatten: FlatText is abstract
 
@@ -533,7 +839,8 @@ abstract class Text
                        # djb2 hash algorithm
                        var h = 5381
 
-                       for char in self.chars do
+                       for i in [0..length[ do
+                               var char = chars[i]
                                h = h.lshift(5) + h + char.ascii
                        end
 
@@ -548,14 +855,33 @@ end
 abstract class FlatText
        super Text
 
-       private var items: NativeString
+       # Underlying C-String (`char*`)
+       #
+       # Warning : Might be void in some subclasses, be sure to check
+       # if set before using it.
+       private var items: NativeString is noinit
 
        # Real items, used as cache for to_cstring is called
        private var real_items: nullable NativeString = null
 
-       redef var length: Int = 0
+       # Returns a char* starting at position `index_from`
+       #
+       # WARNING: If you choose to use this service, be careful of the following.
+       #
+       # Strings and NativeString are *ideally* always allocated through a Garbage Collector.
+       # Since the GC tracks the use of the pointer for the beginning of the char*, it may be
+       # deallocated at any moment, rendering the pointer returned by this function invalid.
+       # Any access to freed memory may very likely cause undefined behaviour or a crash.
+       # (Failure to do so will most certainly result in long and painful debugging hours)
+       #
+       # The only safe use of this pointer is if it is ephemeral (e.g. read in a C function
+       # then immediately return).
+       #
+       # As always, do not modify the content of the String in C code, if this is what you want
+       # copy locally the char* as Nit Strings are immutable.
+       private fun fast_cstring: NativeString is abstract
 
-       init do end
+       redef var length: Int = 0
 
        redef fun output
        do
@@ -576,12 +902,7 @@ private abstract class StringCharView
 
        type SELFTYPE: Text
 
-       private var target: SELFTYPE
-
-       private init(tgt: SELFTYPE)
-       do
-               target = tgt
-       end
+       var target: SELFTYPE
 
        redef fun is_empty do return target.is_empty
 
@@ -602,10 +923,15 @@ private abstract class BufferCharView
 
 end
 
+# A `String` holds and manipulates an arbitrary sequence of characters.
+#
+# String objects may be created using literals.
+#
+#     assert "Hello World!" isa String
 abstract class String
        super Text
 
-       redef type SELFTYPE: String
+       redef type SELFTYPE: String is fixed
 
        redef fun to_s do return self
 
@@ -622,8 +948,13 @@ abstract class String
        #     assert "abc" * 0 == ""
        fun *(i: Int): SELFTYPE is abstract
 
+       # Insert `s` at `pos`.
+       #
+       #     assert "helloworld".insert_at(" ", 5)     == "hello world"
        fun insert_at(s: String, pos: Int): SELFTYPE is abstract
 
+       redef fun substrings: Iterator[String] is abstract
+
        # Returns a reversed version of self
        #
        #     assert "hello".reversed  == "olleh"
@@ -659,7 +990,8 @@ abstract class String
                var new_str = new FlatBuffer.with_capacity(self.length)
                var is_first_char = true
 
-               for char in self.chars do
+               for i in [0..length[ do
+                       var char = chars[i]
                        if is_first_char then 
                                new_str.add(char.to_lower)
                                is_first_char = false
@@ -697,7 +1029,8 @@ abstract class String
                var is_first_char = true
                var follows_us = false
 
-               for char in self.chars do
+               for i in [0..length[ do
+                       var char = chars[i]
                        if is_first_char then
                                new_str.add(char)
                                is_first_char = false
@@ -713,6 +1046,38 @@ abstract class String
 
                return new_str.to_s
        end
+
+       # Returns a capitalized `self`
+       #
+       # Letters that follow a letter are lowercased
+       # Letters that follow a non-letter are upcased.
+       #
+       # SEE : `Char::is_letter` for the definition of letter.
+       #
+       #     assert "jAVASCRIPT".capitalized == "Javascript"
+       #     assert "i am root".capitalized == "I Am Root"
+       #     assert "ab_c -ab0c ab\nc".capitalized == "Ab_C -Ab0C Ab\nC"
+       fun capitalized: SELFTYPE do
+               if length == 0 then return self
+
+               var buf = new FlatBuffer.with_capacity(length)
+
+               var curr = chars[0].to_upper
+               var prev = curr
+               buf[0] = curr
+
+               for i in [1 .. length[ do
+                       prev = curr
+                       curr = self[i]
+                       if prev.is_letter then
+                               buf[i] = curr.to_lower
+                       else
+                               buf[i] = curr.to_upper
+                       end
+               end
+
+               return buf.to_s
+       end
 end
 
 private class FlatSubstringsIter
@@ -720,8 +1085,6 @@ private class FlatSubstringsIter
 
        var tgt: nullable FlatText
 
-       init(tgt: FlatText) do self.tgt = tgt
-
        redef fun item do
                assert is_ok
                return tgt.as(not null)
@@ -738,12 +1101,21 @@ class FlatString
        super String
 
        # Index in _items of the start of the string
-       private var index_from: Int
+       private var index_from: Int is noinit
 
        # Indes in _items of the last item of the string
-       private var index_to: Int
+       private var index_to: Int is noinit
+
+       redef var chars: SequenceRead[Char] = new FlatStringCharView(self) is lazy
 
-       redef var chars: SequenceRead[Char] = new FlatStringCharView(self)
+       redef fun [](index)
+       do
+               # Check that the index (+ index_from) is not larger than indexTo
+               # In other terms, if the index is valid
+               assert index >= 0
+               assert (index + index_from) <= index_to
+               return items[index + index_from]
+       end
 
        ################################################
        #       AbstractString specific methods        #
@@ -751,7 +1123,7 @@ class FlatString
 
        redef fun reversed
        do
-               var native = calloc_string(self.length + 1)
+               var native = new NativeString(self.length + 1)
                var length = self.length
                var items = self.items
                var pos = 0
@@ -764,6 +1136,8 @@ class FlatString
                return native.to_s_with_length(self.length)
        end
 
+       redef fun fast_cstring do return items.fast_cstring(index_from)
+
        redef fun substring(from, count)
        do
                assert count >= 0
@@ -774,22 +1148,26 @@ class FlatString
                        from = 0
                end
 
-               var realFrom = index_from + from
+               var new_from = index_from + from
 
-               if (realFrom + count) > index_to then return new FlatString.with_infos(items, index_to - realFrom + 1, realFrom, index_to)
+               if (new_from + count) > index_to then
+                       var new_len = index_to - new_from + 1
+                       if new_len <= 0 then return empty
+                       return new FlatString.with_infos(items, new_len, new_from, index_to)
+               end
 
-               if count == 0 then return empty
+               if count <= 0 then return empty
 
-               var to = realFrom + count - 1
+               var to = new_from + count - 1
 
-               return new FlatString.with_infos(items, to - realFrom + 1, realFrom, to)
+               return new FlatString.with_infos(items, to - new_from + 1, new_from, to)
        end
 
        redef fun empty do return "".as(FlatString)
 
        redef fun to_upper
        do
-               var outstr = calloc_string(self.length + 1)
+               var outstr = new NativeString(self.length + 1)
                var out_index = 0
 
                var myitems = self.items
@@ -809,7 +1187,7 @@ class FlatString
 
        redef fun to_lower
        do
-               var outstr = calloc_string(self.length + 1)
+               var outstr = new NativeString(self.length + 1)
                var out_index = 0
 
                var myitems = self.items
@@ -841,25 +1219,29 @@ class FlatString
        #              String Specific Methods           #
        ##################################################
 
-       private init with_infos(items: NativeString, len: Int, from: Int, to: Int)
+       # Low-level creation of a new string with given 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 with_infos(items: NativeString, length: Int, from: Int, to: Int)
        do
                self.items = items
-               length = len
+               self.length = length
                index_from = from
                index_to = to
        end
 
        redef fun to_cstring: NativeString
        do
-               if real_items != null then return real_items.as(not null)
-               if index_from > 0 or index_to != items.cstring_length - 1 then
-                       var newItems = calloc_string(length + 1)
+               if real_items != null then
+                       return real_items.as(not null)
+               else
+                       var newItems = new NativeString(length + 1)
                        self.items.copy_to(newItems, length, index_from, 0)
                        newItems[length] = '\0'
                        self.real_items = newItems
                        return newItems
                end
-               return items
        end
 
        redef fun ==(other)
@@ -932,7 +1314,7 @@ class FlatString
 
                var total_length = my_length + its_length
 
-               var target_string = calloc_string(my_length + its_length + 1)
+               var target_string = new NativeString(my_length + its_length + 1)
 
                self.items.copy_to(target_string, my_length, index_from, 0)
                if s isa FlatString then
@@ -941,8 +1323,9 @@ class FlatString
                        s.items.copy_to(target_string, its_length, 0, my_length)
                else
                        var curr_pos = my_length
-                       for i in s.chars do
-                               target_string[curr_pos] = i
+                       for i in [0..s.length[ do
+                               var c = s.chars[i]
+                               target_string[curr_pos] = c
                                curr_pos += 1
                        end
                end
@@ -962,7 +1345,7 @@ class FlatString
 
                var my_items = self.items
 
-               var target_string = calloc_string((final_length) + 1)
+               var target_string = new NativeString(final_length + 1)
 
                target_string[final_length] = '\0'
 
@@ -1015,7 +1398,7 @@ private class FlatStringReverseIterator
                curr_pos = pos + tgt.index_from
        end
 
-       redef fun is_ok do return curr_pos >= 0
+       redef fun is_ok do return curr_pos >= target.index_from
 
        redef fun item do return target_items[curr_pos]
 
@@ -1072,14 +1455,23 @@ private class FlatStringCharView
 
 end
 
+# A mutable sequence of characters.
 abstract class Buffer
        super Text
 
-       redef type SELFTYPE: Buffer
+       redef type SELFTYPE: Buffer is fixed
 
        # Specific implementations MUST set this to `true` in order to invalidate caches
        protected var is_dirty = true
 
+       # Copy-On-Write flag
+       #
+       # If the `Buffer` was to_s'd, the next in-place altering
+       # operation will cause the current `Buffer` to be re-allocated.
+       #
+       # The flag will then be set at `false`.
+       protected var written = false
+
        # Modifies the char contained at pos `index`
        #
        # DEPRECATED : Use self.chars.[]= instead
@@ -1142,6 +1534,38 @@ abstract class Buffer
        #     assert b == "hello world!"
        fun lower is abstract
 
+       # Capitalizes each word in `self`
+       #
+       # Letters that follow a letter are lowercased
+       # Letters that follow a non-letter are upcased.
+       #
+       # SEE: `Char::is_letter` for the definition of a letter.
+       #
+       #     var b = new FlatBuffer.from("jAVAsCriPt")
+       #     b.capitalize
+       #     assert b == "Javascript"
+       #     b = new FlatBuffer.from("i am root")
+       #     b.capitalize
+       #     assert b == "I Am Root"
+       #     b = new FlatBuffer.from("ab_c -ab0c ab\nc")
+       #     b.capitalize
+       #     assert b == "Ab_C -Ab0C Ab\nC"
+       fun capitalize do
+               if length == 0 then return
+               var c = self[0].to_upper
+               self[0] = c
+               var prev = c
+               for i in [1 .. length[ do
+                       prev = c
+                       c = self[i]
+                       if prev.is_letter then
+                               self[i] = c.to_lower
+                       else
+                               self[i] = c.to_upper
+                       end
+               end
+       end
+
        redef fun hash
        do
                if is_dirty then hash_cache = null
@@ -1158,14 +1582,32 @@ class FlatBuffer
        super FlatText
        super Buffer
 
-       redef type SELFTYPE: FlatBuffer
-
-       redef var chars: Sequence[Char] = new FlatBufferCharView(self)
+       redef var chars: Sequence[Char] = new FlatBufferCharView(self) is lazy
 
        private var capacity: Int = 0
 
+       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`
+       #
+       # 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)
+               items.copy_to(nns, length, 0, 0)
+               items = nns
+               written = false
+       end
+
+       redef fun [](index)
+       do
+               assert index >= 0
+               assert index  < length
+               return items[index]
+       end
+
        redef fun []=(index, item)
        do
                is_dirty = true
@@ -1173,6 +1615,7 @@ class FlatBuffer
                        add(item)
                        return
                end
+               if written then reset
                assert index >= 0 and index < length
                items[index] = item
        end
@@ -1187,6 +1630,7 @@ class FlatBuffer
 
        redef fun clear do
                is_dirty = true
+               if written then reset
                length = 0
        end
 
@@ -1197,7 +1641,10 @@ class FlatBuffer
                var c = capacity
                if cap <= c then return
                while c <= cap do c = c * 2 + 2
-               var a = calloc_string(c+1)
+               # The COW flag can be set at false here, since
+               # it does a copy of the current `Buffer`
+               written = false
+               var a = new NativeString(c+1)
                if length > 0 then items.copy_to(a, length, 0, 0)
                items = a
                capacity = c
@@ -1205,13 +1652,15 @@ class FlatBuffer
 
        redef fun to_s: String
        do
-               return to_cstring.to_s_with_length(length)
+               written = true
+               if length == 0 then items = new NativeString(1)
+               return new FlatString.with_infos(items, length, 0, length - 1)
        end
 
        redef fun to_cstring
        do
                if is_dirty then
-                       var new_native = calloc_string(length + 1)
+                       var new_native = new NativeString(length + 1)
                        new_native[length] = '\0'
                        if length > 0 then items.copy_to(new_native, length, 0, 0)
                        real_items = new_native
@@ -1223,19 +1672,35 @@ class FlatBuffer
        # Create a new empty string.
        init do end
 
+       # Low-level creation a new buffer with given data.
+       #
+       # `items` will be used as is, without copy, to store the characters of the buffer.
+       # Aliasing issues is the responsibility of the caller.
+       #
+       # 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, length: Int)
+       do
+               self.items = items
+               self.length = length
+               self.capacity = capacity
+       end
+
+       # Create a new string copied from `s`.
        init from(s: Text)
        do
                capacity = s.length + 1
                length = s.length
-               items = calloc_string(capacity)
+               items = new NativeString(capacity)
                if s isa FlatString then
                        s.items.copy_to(items, length, s.index_from, 0)
                else if s isa FlatBuffer then
                        s.items.copy_to(items, length, 0, 0)
                else
                        var curr_pos = 0
-                       for i in s.chars do
-                               items[curr_pos] = i
+                       for i in [0..s.length[ do
+                               var c = s.chars[i]
+                               items[curr_pos] = c
                                curr_pos += 1
                        end
                end
@@ -1245,8 +1710,7 @@ class FlatBuffer
        init with_capacity(cap: Int)
        do
                assert cap >= 0
-               # _items = new NativeString.calloc(cap)
-               items = calloc_string(cap+1)
+               items = new NativeString(cap+1)
                capacity = cap
                length = 0
        end
@@ -1263,8 +1727,9 @@ class FlatBuffer
                        s.items.copy_to(items, sl, 0, length)
                else
                        var curr_pos = self.length
-                       for i in s.chars do
-                               items[curr_pos] = i
+                       for i in [0..s.length[ do
+                               var c = s.chars[i]
+                               items[curr_pos] = c
                                curr_pos += 1
                        end
                end
@@ -1288,11 +1753,10 @@ class FlatBuffer
                if from < 0 then from = 0
                if count > length then count = length
                if from < count then
-                       var r = new FlatBuffer.with_capacity(count - from)
-                       while from < count do
-                               r.chars.push(items[from])
-                               from += 1
-                       end
+                       var len = count - from
+                       var r_items = new NativeString(len)
+                       items.copy_to(r_items, len, from, 0)
+                       var r = new FlatBuffer.with_infos(r_items, len, len)
                        return r
                else
                        return new FlatBuffer
@@ -1301,7 +1765,8 @@ class FlatBuffer
 
        redef fun reverse
        do
-               var ns = calloc_string(capacity)
+               written = false
+               var ns = new NativeString(capacity)
                var si = length - 1
                var ni = 0
                var it = items
@@ -1323,6 +1788,7 @@ class FlatBuffer
 
        redef fun upper
        do
+               if written then reset
                var it = items
                var id = length - 1
                while id >= 0 do
@@ -1333,6 +1799,7 @@ class FlatBuffer
 
        redef fun lower
        do
+               if written then reset
                var it = items
                var id = length - 1
                while id >= 0 do
@@ -1370,7 +1837,6 @@ end
 
 private class FlatBufferCharView
        super BufferCharView
-       super StringCapable
 
        redef type SELFTYPE: FlatBuffer
 
@@ -1403,7 +1869,6 @@ private class FlatBufferCharView
 
        redef fun append(s)
        do
-               var my_items = target.items
                var s_length = s.length
                if target.capacity < s.length then enlarge(s_length + target.length)
        end
@@ -1453,7 +1918,7 @@ redef class Object
 
        # The class name of the object.
        #
-       #    assert 5.class_name == "Int"
+       #     assert 5.class_name == "Int"
        fun class_name: String do return native_class_name.to_s
 
        # Developer readable representation of `self`.
@@ -1487,9 +1952,7 @@ end
 redef class Int
 
        # Wrapper of strerror C function
-       private fun strerror_ext: NativeString is extern `{
-               return strerror(recv);
-       `}
+       private fun strerror_ext: NativeString is extern "strerror"
 
        # Returns a string describing error number
        fun strerror: String do return strerror_ext.to_s
@@ -1518,15 +1981,26 @@ redef class Int
                end
        end
 
+       # C function to calculate the length of the `NativeString` to receive `self`
+       private fun int_to_s_len: Int is extern "native_int_length_str"
+
        # C function to convert an nit Int to a NativeString (char*)
-       private fun native_int_to_s: NativeString is extern "native_int_to_s"
+       private fun native_int_to_s(nstr: NativeString, strlen: Int) is extern "native_int_to_s"
 
        # return displayable int in base 10 and signed
        #
        #     assert 1.to_s            == "1"
        #     assert (-123).to_s       == "-123"
        redef fun to_s do
-               return native_int_to_s.to_s
+               # Fast case for common numbers
+               if self == 0 then return "0"
+               if self == 1 then return "1"
+
+               var nslen = int_to_s_len
+               var ns = new NativeString(nslen + 1)
+               ns[nslen] = '\0'
+               native_int_to_s(ns, nslen + 1)
+               return ns.to_s_with_length(nslen)
        end
 
        # return displayable int in hexadecimal
@@ -1546,12 +2020,12 @@ redef class Int
 end
 
 redef class Float
-       # Pretty print self, print needoed decimals up to a max of 3.
+       # Pretty representation of `self`, with decimals as needed from 1 to a maximum of 3
        #
-       #     assert 12.34.to_s        == "12.34"
-       #     assert (-0120.03450).to_s  == "-120.035"
+       #     assert 12.34.to_s       == "12.34"
+       #     assert (-0120.030).to_s == "-120.03"
        #
-       # see `to_precision` for a different precision.
+       # see `to_precision` for a custom precision.
        redef fun to_s do
                var str = to_precision( 3 )
                if is_inf != 0 or is_nan then return str
@@ -1570,13 +2044,15 @@ redef class Float
                return str
        end
 
-       # `self` representation with `nb` digits after the '.'.
+       # `String` representation of `self` with the given number of `decimals`
        #
-       #     assert 12.345.to_precision(1) == "12.3"
-       #     assert 12.345.to_precision(2) == "12.35"
-       #     assert 12.345.to_precision(3) == "12.345"
-       #     assert 12.345.to_precision(4) == "12.3450"
-       fun to_precision(nb: Int): String
+       #     assert 12.345.to_precision(0)    == "12"
+       #     assert 12.345.to_precision(3)    == "12.345"
+       #     assert (-12.345).to_precision(3) == "-12.345"
+       #     assert (-0.123).to_precision(3)  == "-0.123"
+       #     assert 0.999.to_precision(2)     == "1.00"
+       #     assert 0.999.to_precision(4)     == "0.9990"
+       fun to_precision(decimals: Int): String
        do
                if is_nan then return "nan"
 
@@ -1587,43 +2063,35 @@ redef class Float
                        return  "-inf"
                end
 
-               if nb == 0 then return self.to_i.to_s
+               if decimals == 0 then return self.to_i.to_s
                var f = self
-               for i in [0..nb[ do f = f * 10.0
+               for i in [0..decimals[ do f = f * 10.0
                if self > 0.0 then
                        f = f + 0.5
                else
                        f = f - 0.5
                end
                var i = f.to_i
-               if i == 0 then return "0.0"
-               var s = i.to_s
+               if i == 0 then return "0." + "0"*decimals
+
+               # Prepare both parts of the float, before and after the "."
+               var s = i.abs.to_s
                var sl = s.length
-               if sl > nb then
-                       var p1 = s.substring(0, s.length-nb)
-                       var p2 = s.substring(s.length-nb, nb)
-                       return p1 + "." + p2
+               var p1
+               var p2
+               if sl > decimals then
+                       # Has something before the "."
+                       p1 = s.substring(0, sl-decimals)
+                       p2 = s.substring(sl-decimals, decimals)
                else
-                       return "0." + ("0"*(nb-sl)) + s
+                       p1 = "0"
+                       p2 = "0"*(decimals-sl) + s
                end
-       end
-
-       # `self` representation with `nb` digits after the '.'.
-       #
-       #     assert 12.345.to_precision_native(1) == "12.3"
-       #     assert 12.345.to_precision_native(2) == "12.35"
-       #     assert 12.345.to_precision_native(3) == "12.345"
-       #     assert 12.345.to_precision_native(4) == "12.3450"
-       fun to_precision_native(nb: Int): String import NativeString.to_s `{
-               int size;
-               char *str;
 
-               size = snprintf(NULL, 0, "%.*f", (int)nb, recv);
-               str = malloc(size + 1);
-               sprintf(str, "%.*f", (int)nb, recv );
+               if i < 0 then p1 = "-" + p1
 
-               return NativeString_to_s( str );
-       `}
+               return p1 + "." + p2
+       end
 end
 
 redef class Char
@@ -1637,10 +2105,10 @@ redef class Char
 
        # Returns true if the char is a numerical digit
        #
-       #      assert '0'.is_numeric
-       #      assert '9'.is_numeric
-       #      assert not 'a'.is_numeric
-       #      assert not '?'.is_numeric
+       #     assert '0'.is_numeric
+       #     assert '9'.is_numeric
+       #     assert not 'a'.is_numeric
+       #     assert not '?'.is_numeric
        fun is_numeric: Bool
        do
                return self >= '0' and self <= '9'
@@ -1648,10 +2116,10 @@ redef class Char
 
        # Returns true if the char is an alpha digit
        #
-       #      assert 'a'.is_alpha
-       #      assert 'Z'.is_alpha
-       #      assert not '0'.is_alpha
-       #      assert not '?'.is_alpha
+       #     assert 'a'.is_alpha
+       #     assert 'Z'.is_alpha
+       #     assert not '0'.is_alpha
+       #     assert not '?'.is_alpha
        fun is_alpha: Bool
        do
                return (self >= 'a' and self <= 'z') or (self >= 'A' and self <= 'Z')
@@ -1659,11 +2127,11 @@ redef class Char
 
        # Returns true if the char is an alpha or a numeric digit
        #
-       #      assert 'a'.is_alphanumeric
-       #      assert 'Z'.is_alphanumeric
-       #      assert '0'.is_alphanumeric
-       #      assert '9'.is_alphanumeric
-       #      assert not '?'.is_alphanumeric
+       #     assert 'a'.is_alphanumeric
+       #     assert 'Z'.is_alphanumeric
+       #     assert '0'.is_alphanumeric
+       #     assert '9'.is_alphanumeric
+       #     assert not '?'.is_alphanumeric
        fun is_alphanumeric: Bool
        do
                return self.is_numeric or self.is_alpha
@@ -1707,18 +2175,93 @@ redef class Collection[E]
 end
 
 redef class Array[E]
+
        # Fast implementation
        redef fun to_s
        do
-               var s = new FlatBuffer
+               var l = length
+               if l == 0 then return ""
+               if l == 1 then if self[0] == null then return "" else return self[0].to_s
+               var its = _items
+               var na = new NativeArray[String](l)
                var i = 0
+               var sl = 0
+               var mypos = 0
+               while i < l do
+                       var itsi = its[i]
+                       if itsi == null then
+                               i += 1
+                               continue
+                       end
+                       var tmp = itsi.to_s
+                       sl += tmp.length
+                       na[mypos] = tmp
+                       i += 1
+                       mypos += 1
+               end
+               var ns = new NativeString(sl + 1)
+               ns[sl] = '\0'
+               i = 0
+               var off = 0
+               while i < mypos do
+                       var tmp = na[i]
+                       var tpl = tmp.length
+                       if tmp isa FlatString then
+                               tmp.items.copy_to(ns, tpl, tmp.index_from, off)
+                               off += tpl
+                       else
+                               for j in tmp.substrings do
+                                       var s = j.as(FlatString)
+                                       var slen = s.length
+                                       s.items.copy_to(ns, slen, s.index_from, off)
+                                       off += slen
+                               end
+                       end
+                       i += 1
+               end
+               return ns.to_s_with_length(sl)
+       end
+end
+
+redef class NativeArray[E]
+       # Join all the elements using `to_s`
+       #
+       # REQUIRE: `self isa NativeArray[String]`
+       # REQUIRE: all elements are initialized
+       fun native_to_s: String
+       do
+               assert self isa NativeArray[String]
                var l = length
+               var na = self
+               var i = 0
+               var sl = 0
+               var mypos = 0
                while i < l do
-                       var e = self[i]
-                       if e != null then s.append(e.to_s)
+                       sl += na[i].length
                        i += 1
+                       mypos += 1
                end
-               return s.to_s
+               var ns = new NativeString(sl + 1)
+               ns[sl] = '\0'
+               i = 0
+               var off = 0
+               while i < mypos do
+                       var tmp = na[i]
+                       var tpl = tmp.length
+                       if tmp isa FlatString then
+                               tmp.items.copy_to(ns, tpl, tmp.index_from, off)
+                               off += tpl
+                       else
+                               for j in tmp.substrings do
+                                       var s = j.as(FlatString)
+                                       var slen = s.length
+                                       s.items.copy_to(ns, slen, s.index_from, off)
+                                       off += slen
+                               end
+                       end
+                       i += 1
+               end
+               return ns.to_s_with_length(sl)
        end
 end
 
@@ -1741,7 +2284,7 @@ redef class Map[K,V]
                var i = iterator
                var k = i.key
                var e = i.item
-               s.append("{k}{couple_sep}{e or else "<null>"}")
+               s.append("{k or else "<null>"}{couple_sep}{e or else "<null>"}")
 
                # Concat other items
                i.next
@@ -1749,7 +2292,7 @@ redef class Map[K,V]
                        s.append(sep)
                        k = i.key
                        e = i.item
-                       s.append("{k}{couple_sep}{e or else "<null>"}")
+                       s.append("{k or else "<null>"}{couple_sep}{e or else "<null>"}")
                        i.next
                end
                return s.to_s
@@ -1762,10 +2305,22 @@ end
 
 # Native strings are simple C char *
 extern class NativeString `{ char* `}
-       super StringCapable
+       # Creates a new NativeString with a capacity of `length`
+       new(length: Int) is intern
 
+       # Returns a char* starting at `index`.
+       #
+       # WARNING: Unsafe for extern code, use only for temporary
+       # pointer manipulation purposes (e.g. write to file or such)
+       fun fast_cstring(index: Int): NativeString is intern
+
+       # Get char at `index`.
        fun [](index: Int): Char is intern
+
+       # Set char `item` at index.
        fun []=(index: Int, item: Char) is intern
+
+       # Copy `self` to `dest`.
        fun copy_to(dest: NativeString, length: Int, from: Int, to: Int) is intern
 
        # Position of the first nul character.
@@ -1775,7 +2330,11 @@ extern class NativeString `{ char* `}
                while self[l] != '\0' do l += 1
                return l
        end
+
+       # Parse `self` as an Int.
        fun atoi: Int is intern
+
+       # Parse `self` as a Float.
        fun atof: Float is extern "atof"
 
        redef fun to_s
@@ -1783,28 +2342,29 @@ extern class NativeString `{ char* `}
                return to_s_with_length(cstring_length)
        end
 
+       # Returns `self` as a String of `length`.
        fun to_s_with_length(length: Int): FlatString
        do
                assert length >= 0
-               return new FlatString.with_infos(self, length, 0, length - 1)
+               var str = new FlatString.with_infos(self, length, 0, length - 1)
+               return str
        end
 
+       # Returns `self` as a new String.
        fun to_s_with_copy: FlatString
        do
                var length = cstring_length
-               var new_self = calloc_string(length + 1)
+               var new_self = new NativeString(length + 1)
                copy_to(new_self, length, 0, 0)
-               return new FlatString.with_infos(new_self, length, 0, length - 1)
+               var str = new FlatString.with_infos(new_self, length, 0, length - 1)
+               new_self[length] = '\0'
+               str.real_items = new_self
+               return str
        end
 end
 
-# StringCapable objects can create native strings
-interface StringCapable
-       protected fun calloc_string(size: Int): NativeString is intern
-end
-
 redef class Sys
-       var _args_cache: nullable Sequence[String]
+       private var args_cache: nullable Sequence[String]
 
        # The arguments of the program as given by the OS
        fun program_args: Sequence[String]
@@ -1852,7 +2412,8 @@ end
 #
 # Note: it caching is not usefull, see `alpha_comparator`
 class CachedAlphaComparator
-       super Comparator[Object]
+       super Comparator
+       redef type COMPARED: Object
 
        private var cache = new HashMap[Object, String]
 
@@ -1870,7 +2431,7 @@ end
 
 # see `alpha_comparator`
 private class AlphaComparator
-       super Comparator[Object]
+       super Comparator
        redef fun compare(a, b) do return a.to_s <=> b.to_s
 end
 
@@ -1882,7 +2443,7 @@ end
 #     var a = [1, 2, 3, 10, 20]
 #     alpha_comparator.sort(a)
 #     assert a == [1, 10, 2, 20, 3]
-fun alpha_comparator: Comparator[Object] do return once new AlphaComparator
+fun alpha_comparator: Comparator do return once new AlphaComparator
 
 # The arguments of the program as given by the OS
 fun args: Sequence[String]