deepCopy

[Denis Koroskin]

On Tue, 19 Oct 2010 12:37:35 +0400, Jacob Carlborg <doob at me.com> wrote:

> On 2010-10-19 00:01, Denis Koroskin wrote:
>> Okay, we've finished what we started with Aleksey today, so I decided to
>> share it with you. This is a rough cut, it lacks comments, but it is
>> already usable.
>>
>> deepCopy is a function that makes a deep copy of your object, and
>> everything it points to. As simple as that.
>>
>> Essentially it is a binary serializer except that it doesn't store
>> pointers as offsets (although it is capable of doing that, too - change
>> a single line - so serialize and deepCopy share 99% of the code).
>>
>> deepCopy and serialize are similar in design yet different in usage:
>> serialized data are usually transmitted to other application, and one
>> must worry about different endianness, pointer size etc. On the contrary
>> deepCopy is to be used within the same address space and is free from
>> such issues.
>>
>> deepCopy is useful for making sure there are no aliases to your data
>> left. This can be used to create a safe immutable copy of your objects,
>> or to avoid with memory leaks.
>>
>> We've written deepCopy to solve memory leaks in ddmd the following way:
>> a) hook all the memory allocations
>> b) run code, produce result
>> c) make a deep copy of the result
>> d) release all the allocated memory
>>
>> Since you are deallocating all the memory at once, you can use faster
>> allocation methods e.g preallocate a memory and simply advance a
>> pointer, or use dsimcha's tempAlloc
>> (http://dsource.org/projects/scrapple/browser/trunk/tempAlloc). BTW, I
>> remember a discussion about integrating it into druntime, did it go
>> anywhere since then?.
>>
>> deepCopy stores all the data sequentially, so it should reduce memory
>> fragmentation and should be more cache-friendly. As a downside, the
>> whole block will only be release once last reference to it expires.
>>
>> If your struct has pointers you can manually specify if that pointer is
>> a pointer to one element (default), many or none (excluding it from
>> being copied). Exclusion works with references, too:
>>
>> class Foo : ISerializeable
>> {
>> mixin Serializeable;
>>
>> // optional, only needed for precise serialization control
>> void describe(SerializeInfo* info)
>> {
>> info.setLength(buffer, length);
>> info.exclude(cachedValue);
>> }
>>
>> ubyte* buffer;
>> size_t length;
>> Object cachedValue;
>> }
>>
>> I hope someone will find it useful, the code with tests is located here:
>> http://bitbucket.org/korDen/serialize/src/tip/
>>
>> Suggestions are welcome!
>
> What types does this support, all types? Does it support array slices?
>

Classes, structs, built-in types, arrays, slices - just about anything.  
For classes to work you need to implement ISerializable interface using  
mixin Serializable; so that it could serialize through base class pointer.

Not that I think about it, it doesn't support built-in associative arrays  
yet. I forgot about that one (it might be tricky to serialize it into a  
sequential memory block). Take a loot at the tests (there are many of  
them, some of them are very tricky), and give it a try.