lib/core: Optimized `html_escape` for FlatText variants
[nit.git] / lib / core / text / flat.nit
index c8b6ecd..c89b222 100644 (file)
@@ -36,18 +36,18 @@ end
 
 redef class FlatText
 
-       private fun first_byte: Int do return 0
+       fun first_byte: Int do return 0
 
-       private fun last_byte: Int do return _bytelen - 1
+       fun last_byte: Int do return _bytelen - 1
 
        # Cache of the latest position (char) explored in the string
-       private var position: Int = 0
+       var position: Int = 0
 
        # Cached position (bytes) in the NativeString underlying the String
-       private var bytepos: Int = 0
+       var bytepos: Int = 0
 
        # Index of the character `index` in `_items`
-       private fun char_to_byte_index(index: Int): Int do
+       fun char_to_byte_index(index: Int): Int do
                var ln = length
                assert index >= 0
                assert index < ln
@@ -85,12 +85,110 @@ redef class FlatText
                return ns_i
        end
 
+       # By escaping `self` to HTML, how many more bytes will be needed ?
+       fun chars_to_html_escape: Int do
+               var its = _items
+               var max = last_byte
+               var pos = first_byte
+               var endlen = 0
+               while pos <= max do
+                       var c = its[pos]
+                       if c == 0x3Cu8 then
+                               endlen += 3
+                       else if c == 0x3Eu8 then
+                               endlen += 3
+                       else if c == 0x26u8 then
+                               endlen += 4
+                       else if c == 0x22u8 then
+                               endlen += 4
+                       else if c == 0x27u8 then
+                               endlen += 4
+                       else if c == 0x2Fu8 then
+                               endlen += 4
+                       end
+                       pos += 1
+               end
+               return endlen
+       end
+
+       redef fun html_escape
+       do
+               var extra = chars_to_html_escape
+               if extra == 0 then return to_s
+               var its = _items
+               var max = last_byte
+               var pos = first_byte
+               var nlen = extra + _bytelen
+               var nits = new NativeString(nlen)
+               var outpos = 0
+               while pos <= max do
+                       var c = its[pos]
+                       # Special codes:
+                       # Some HTML characters are used as meta-data, they need
+                       # to be replaced by an HTML-Escaped equivalent
+                       #
+                       # * 0x3C (<) => &lt;
+                       # * 0x3E (>) => &gt;
+                       # * 0x26 (&) => &amp;
+                       # * 0x22 (") => &#34;
+                       # * 0x27 (') => &#39;
+                       # * 0x2F (/) => &#47;
+                       if c == 0x3Cu8 then
+                               nits[outpos] = 0x26u8
+                               nits[outpos + 1] = 0x6Cu8
+                               nits[outpos + 2] = 0x74u8
+                               nits[outpos + 3] = 0x3Bu8
+                               outpos += 4
+                       else if c == 0x3Eu8 then
+                               nits[outpos] = 0x26u8
+                               nits[outpos + 1] = 0x67u8
+                               nits[outpos + 2] = 0x74u8
+                               nits[outpos + 3] = 0x3Bu8
+                               outpos += 4
+                       else if c == 0x26u8 then
+                               nits[outpos] = 0x26u8
+                               nits[outpos + 1] = 0x61u8
+                               nits[outpos + 2] = 0x6Du8
+                               nits[outpos + 3] = 0x70u8
+                               nits[outpos + 4] = 0x3Bu8
+                               outpos += 5
+                       else if c == 0x22u8 then
+                               nits[outpos] = 0x26u8
+                               nits[outpos + 1] = 0x23u8
+                               nits[outpos + 2] = 0x33u8
+                               nits[outpos + 3] = 0x34u8
+                               nits[outpos + 4] = 0x3Bu8
+                               outpos += 5
+                       else if c == 0x27u8 then
+                               nits[outpos] = 0x26u8
+                               nits[outpos + 1] = 0x23u8
+                               nits[outpos + 2] = 0x33u8
+                               nits[outpos + 3] = 0x39u8
+                               nits[outpos + 4] = 0x3Bu8
+                               outpos += 5
+                       else if c == 0x2Fu8 then
+                               nits[outpos] = 0x26u8
+                               nits[outpos + 1] = 0x23u8
+                               nits[outpos + 2] = 0x34u8
+                               nits[outpos + 3] = 0x37u8
+                               nits[outpos + 4] = 0x3Bu8
+                               outpos += 5
+                       else
+                               nits[outpos] = c
+                               outpos += 1
+                       end
+                       pos += 1
+               end
+               var s = new FlatString.with_infos(nits, nlen, 0, nlen - 1)
+               return s
+       end
+
        # By escaping `self` to C, how many more bytes will be needed ?
        #
        # This enables a double-optimization in `escape_to_c` since if this
        # method returns 0, then `self` does not need escaping and can be
        # returned as-is
-       protected fun chars_to_escape_to_c: Int do
+       fun chars_to_escape_to_c: Int do
                var its = _items
                var max = last_byte
                var pos = first_byte
@@ -200,6 +298,14 @@ class FlatString
                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)
+               _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)
@@ -304,16 +410,6 @@ class FlatString
                _bytepos = from
        end
 
-       redef fun to_cstring do
-               if real_items != null then return real_items.as(not null)
-               var blen = _bytelen
-               var new_items = new NativeString(blen + 1)
-               _items.copy_to(new_items, blen, _first_byte, 0)
-               new_items[blen] = 0u8
-               real_items = new_items
-               return new_items
-       end
-
        redef fun ==(other)
        do
                if not other isa FlatString then return super
@@ -582,6 +678,9 @@ class FlatBuffer
 
        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)
@@ -702,7 +801,7 @@ class FlatBuffer
                        real_items = new_native
                        is_dirty = false
                end
-               return real_items.as(not null)
+               return real_items
        end
 
        # Create a new empty string.
@@ -985,8 +1084,7 @@ redef class NativeString
        redef fun to_s_with_length(length): FlatString
        do
                assert length >= 0
-               var str = new FlatString.with_infos(self, length, 0, length - 1)
-               return str
+               return clean_utf8(length)
        end
 
        redef fun to_s_full(bytelen, unilen) do
@@ -997,14 +1095,91 @@ redef class NativeString
        redef fun to_s_with_copy: FlatString
        do
                var length = cstring_length
+               var r = clean_utf8(length)
+               if r.items != self then return r
                var new_self = new NativeString(length + 1)
                copy_to(new_self, length, 0, 0)
                var str = new FlatString.with_infos(new_self, length, 0, length - 1)
                new_self[length] = 0u8
-               str.real_items = new_self
+               str.to_cstring = new_self
                return str
        end
 
+       # Cleans a NativeString 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 b = self[pos]
+                       var nxst = length_of_char_at(pos)
+                       var ok_st: Bool
+                       if nxst == 1 then
+                               ok_st = b & 0x80u8 == 0u8
+                       else if nxst == 2 then
+                               ok_st = b & 0xE0u8 == 0xC0u8
+                       else if nxst == 3 then
+                               ok_st = b & 0xF0u8 == 0xE0u8
+                       else
+                               ok_st = b & 0xF8u8 == 0xF0u8
+                       end
+                       if not ok_st then
+                               if replacements == null then replacements = new Array[Int]
+                               replacements.add pos
+                               end_length += 2
+                               pos += 1
+                               chr_ln += 1
+                               continue
+                       end
+                       var ok_c: Bool
+                       var c = char_at(pos)
+                       var cp = c.code_point
+                       if nxst == 1 then
+                               ok_c = cp >= 0 and cp <= 0x7F
+                       else if nxst == 2 then
+                               ok_c = cp >= 0x80 and cp <= 0x7FF
+                       else if nxst == 3 then
+                               ok_c = cp >= 0x800 and cp <= 0xFFFF
+                               ok_c = ok_c and not (cp >= 0xD800 and cp <= 0xDFFF) and cp != 0xFFFE and cp != 0xFFFF
+                       else
+                               ok_c = cp >= 0x10000 and cp <= 0x10FFFF
+                       end
+                       if not ok_c then
+                               if replacements == null then replacements = new Array[Int]
+                               replacements.add pos
+                               end_length += 2
+                               pos += 1
+                               chr_ln += 1
+                               continue
+                       end
+                       pos += c.u8char_len
+                       chr_ln += 1
+               end
+               var ret = self
+               if end_length != len then
+                       ret = new NativeString(end_length)
+                       var old_repl = 0
+                       var off = 0
+                       var repls = replacements.as(not null)
+                       var r = repls.items.as(not null)
+                       var imax = repls.length
+                       for i in [0 .. imax[ do
+                               var repl_pos = r[i]
+                               var chkln = repl_pos - old_repl
+                               copy_to(ret, chkln, old_repl, off)
+                               off += chkln
+                               ret[off] = 0xEFu8
+                               ret[off + 1] = 0xBFu8
+                               ret[off + 2] = 0xBDu8
+                               old_repl = repl_pos + 1
+                               off += 3
+                       end
+                       copy_to(ret, len - old_repl, old_repl, off)
+               end
+               return new FlatString.full(ret, end_length, 0, end_length - 1, 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.
@@ -1071,8 +1246,9 @@ redef class Array[E]
        do
                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 its = _items.as(not null)
+               var first = its[0]
+               if l == 1 then if first == null then return "" else return first.to_s
                var na = new NativeArray[String](l)
                var i = 0
                var sl = 0
@@ -1109,7 +1285,7 @@ redef class Array[E]
                        end
                        i += 1
                end
-               return ns.to_s_with_length(sl)
+               return new FlatString.with_infos(ns, sl, 0, sl - 1)
        end
 end
 
@@ -1146,7 +1322,7 @@ redef class NativeArray[E]
                        end
                        i += 1
                end
-               return ns.to_s_with_length(sl)
+               return new FlatString.with_infos(ns, sl, 0, sl - 1)
        end
 end