lib/standard/string: Introducting Copy-on-Write FlatBuffers

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>

diff --git a/lib/standard/string.nit b/lib/standard/string.nit
index 70cf816..d41ab1a 100644 (file)
--- a/lib/standard/string.nit
+++ b/lib/standard/string.nit
@@ -971,15 +971,15 @@ class FlatString
 
        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
+               if real_items != null then
+                       return real_items.as(not null)
+               else
                        var newItems = calloc_string(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)
@@ -1201,6 +1201,14 @@ abstract class Buffer
        # 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
@@ -1287,6 +1295,17 @@ class FlatBuffer
 
        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
@@ -1301,6 +1320,7 @@ class FlatBuffer
                        add(item)
                        return
                end
+               if written then reset
                assert index >= 0 and index < length
                items[index] = item
        end
@@ -1315,6 +1335,7 @@ class FlatBuffer
 
        redef fun clear do
                is_dirty = true
+               if written then reset
                length = 0
        end
 
@@ -1325,6 +1346,9 @@ class FlatBuffer
                var c = capacity
                if cap <= c then return
                while c <= cap do c = c * 2 + 2
+               # The COW flag can be set at false here, since
+               # it does a copy of the current `Buffer`
+               written = false
                var a = calloc_string(c+1)
                if length > 0 then items.copy_to(a, length, 0, 0)
                items = a
@@ -1333,7 +1357,8 @@ class FlatBuffer
 
        redef fun to_s: String
        do
-               return to_cstring.to_s_with_length(length)
+               written = true
+               return new FlatString.with_infos(items, length, 0, length - 1)
        end
 
        redef fun to_cstring
@@ -1431,6 +1456,7 @@ class FlatBuffer
 
        redef fun reverse
        do
+               written = false
                var ns = calloc_string(capacity)
                var si = length - 1
                var ni = 0
@@ -1453,6 +1479,7 @@ class FlatBuffer
 
        redef fun upper
        do
+               if written then reset
                var it = items
                var id = length - 1
                while id >= 0 do
@@ -1463,6 +1490,7 @@ class FlatBuffer
 
        redef fun lower
        do
+               if written then reset
                var it = items
                var id = length - 1
                while id >= 0 do

diff --git a/lib/string_experimentations/utf8.nit b/lib/string_experimentations/utf8.nit
index 7261820..ccc3391 100644 (file)
--- a/lib/string_experimentations/utf8.nit
+++ b/lib/string_experimentations/utf8.nit
@@ -354,6 +354,20 @@ redef class FlatString
 
 end
 
+redef class FlatBuffer
+
+       # Fix for this particular implementation
+       #
+       # Since the to_s of a FlatBuffer now builds using
+       # the old String contructor, this breaks everything.
+       #
+       # This will disappear when UTF8 is fully-supported
+       redef fun to_s do
+               written = false
+               return to_cstring.to_s_with_length(length)
+       end
+end
+
 redef class NativeString
 
        # Creates the index for said NativeString