Re: An interessting change for shared char[] in String/StringBuffer

[Thomas Zander]

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On Thursday 08 April 2004 15:24, Eric Blake wrote:
> Tom Tromey wrote:

> I also wonder if the following implementation would be more efficient. 
> In the common case, StringBuffer/StringBuilder is used for appends, and
> then converted to a String just before being discarded.  Currently, for
> every append, we adjust the underlying char[] and copy the appended
> String into that array.  Would it be better ...

An alternate approach;
some time ago I noticed that the ByteArrayOutputStream copied all data 
already present on each add, which is when we came up with the following 
approach that would be usefull here as well;

Use a list of byte[] 's (or char[]'s) and optimistically allocate space in 
the first array.
At appends copy all the bytes that will fit into the already allocated 
byte[], and allocate a second one for the rest.  Use some algoritm that 
allocates based on previous size (say; 20% of current size) so you will 
get increasingly bigger arrays which you copy into.

At the end you will have a list of arrays which you can copy into one big 
array on toString() or similar.

We found that this is the most effecient way of accumulating data in one 
class with minimum garbage collection / allocations.

Hope thats clear.
- -- 
Thomas
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