Hello,
Could someone please review or comment on this simple patch I've already
posted twice? Thanks!
- Juraj
--- Begin Message ---
Hello,
Attached you'll find a patch which reduces the number of allocations
done in String.Replace and StringBuilder.Replace.
All unit tests pass, ChangeLog entries are included.
Please review.
- Juraj
PS: I've already posted this patch back in June, but this time I've
leaving out the controversial part.
http://lists.ximian.com/pipermail/mono-devel-list/2008-June/028239.html
Index: corlib/System/ChangeLog
===================================================================
--- corlib/System/ChangeLog (revision 112532)
+++ corlib/System/ChangeLog (working copy)
@@ -1,3 +1,8 @@
+2008-09-08 Juraj Skripsky <[EMAIL PROTECTED]>
+
+ * String.cs (ReplaceUnchecked): Avoid any unnecessary work and
+ string allocations by returning early when no oldValue was found.
+
2008-09-07 Miguel de Icaza <[EMAIL PROTECTED]>
* TermInfoDriver.cs: Add support for updating the size of the
Index: corlib/System/String.cs
===================================================================
--- corlib/System/String.cs (revision 112532)
+++ corlib/System/String.cs (working copy)
@@ -1689,6 +1689,8 @@
}
i = found + oldValue.length;
}
+ if (count == 0)
+ return this;
int nlen = this.length + ((newValue.length - oldValue.length) * count);
String tmp = InternalAllocateStr (nlen);
Index: corlib/System.Text/StringBuilder.cs
===================================================================
--- corlib/System.Text/StringBuilder.cs (revision 112532)
+++ corlib/System.Text/StringBuilder.cs (working copy)
@@ -309,15 +309,22 @@
if (oldValue.Length == 0)
throw new ArgumentException ("The old value cannot be zero length.");
- // TODO: OPTIMIZE!
- string replace = _str.Substring(startIndex, count).Replace(oldValue, newValue);
+ string substr = _str.Substring(startIndex, count);
+ string replace = substr.Replace(oldValue, newValue);
+ // return early if no oldValue was found
+ if ((object) replace == (object) substr)
+ return this;
InternalEnsureCapacity (replace.Length + (_length - count));
- string end = _str.Substring (startIndex + count, _length - startIndex - count );
+ // shift end part
+ if (replace.Length < count)
+ String.CharCopy (_str, startIndex + replace.Length, _str, startIndex + count, _length - startIndex - count);
+ else if (replace.Length > count)
+ String.CharCopyReverse (_str, startIndex + replace.Length, _str, startIndex + count, _length - startIndex - count);
+ // copy middle part back into _str
String.CharCopy (_str, startIndex, replace, 0, replace.Length);
- String.CharCopy (_str, startIndex + replace.Length, end, 0, end.Length);
_length = replace.Length + (_length - count);
Index: corlib/System.Text/ChangeLog
===================================================================
--- corlib/System.Text/ChangeLog (revision 112532)
+++ corlib/System.Text/ChangeLog (working copy)
@@ -1,3 +1,8 @@
+2008-09-08 Juraj Skripsky <[EMAIL PROTECTED]>
+
+ * StringBuilder.cs (Replace): Return early when no oldValue was
+ found. Avoid extra string allocations.
+
2008-07-03 Andreas Nahr <[EMAIL PROTECTED]>
* UTF8Encoding.cs: Fix parameter names, Remove unfounded TODO
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