TArray Indexing Order(Question) ?

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bolvai
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TArray Indexing Order(Question) ?

Post by bolvai »

Can someone explain me why FName in TArray, like that

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TArray<FName>			NameMap;
are being indexed with different order then they was originaly ?
For example first name in NameTable is

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none 
it has order "0", in Tarray<FName> it would too have index "0".
But Then goes second name

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Quat
it has order "7", but in Tarray<FName> it has index of "1515", why its not indexing it according to its order ?

And how the ULinker::Saver knows that object in package that is being saved on HDD, must write value of order but not of index of the array what is used for this?
Higor
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Re: TArray Indexing Order(Question) ?

Post by Higor »

First things first, where is that line of code defined at?
Secondly, FName is serialized in a VERY particular way in a package...
bolvai
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Re: TArray Indexing Order(Question) ?

Post by bolvai »

if you are talking about TArray<FName> NameMap;
its defined in UnLinker.Cpp

And about second !i still dont get why its different value in array then value writed on disk(representing FName Pointer to NameTable) why is that ?
bolvai
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Re: TArray Indexing Order(Question) ?

Post by bolvai »

I dont understand where are the Fnames Values from Disk are being readed by function and changed to other value.
Higor
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Re: TArray Indexing Order(Question) ?

Post by Higor »

Because all names except the hardcoded ones are allocated dynamically.
And not all names in a package exist in runtime, therefore they have to be created and listed in a free slot.

The way to make proper name saving on package, is to use a local table and then save the name ID whenever some code or property wants to use it.
https://wiki.beyondunreal.com/Legacy:Pa ... ile_Format
- The order of the tables doesn't have to be as said there, but some incomplete programs may crash if that's not the case.
- Name table has to be fully parsed before anything else is serialized, becuase it's saved in compact mode (flags: 4 bytes, name: n bytes, 0 ending char) and cannot be 'lazy loaded' whenever a name has to be retrieved.
- Code and properties will save names as a local table index, being said local table the one on the name table.
bolvai
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Re: TArray Indexing Order(Question) ?

Post by bolvai »

Higor wrote:Because all names except the hardcoded ones are allocated dynamically.
And not all names in a package exist in runtime, therefore they have to be created and listed in a free slot.

The way to make proper name saving on package, is to use a local table and then save the name ID whenever some code or property wants to use it.
https://wiki.beyondunreal.com/Legacy:Pa ... ile_Format
- The order of the tables doesn't have to be as said there, but some incomplete programs may crash if that's not the case.
- Name table has to be fully parsed before anything else is serialized, becuase it's saved in compact mode (flags: 4 bytes, name: n bytes, 0 ending char) and cannot be 'lazy loaded' whenever a name has to be retrieved.
- Code and properties will save names as a local table index, being said local table the one on the name table.
But can you tell me were the reading from disk take place in FName, i mean the value from the local table should be parsed somewhere, and were this is going ?
bolvai
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Re: TArray Indexing Order(Question) ?

Post by bolvai »

Well anyway i made an hacker* way to get real INT value of FName, rewriting original Serializer, but i have 1 big problem i dont use original Farchive Serializer to save output, i just use WriteFile(Filename, &ImportTable.Classname,sizeof(classname)). And the problem here is that value is writed not as FcompactIndex but just as INT, so for example 233 it writes like E9, instead of 69 03, thats because im not using FcompactIndex serialization, so can someone help me with that?
I was trying to make that sort of macro , but it returns me only 1 Byte, how can i return an Array of Bytes, i was trying to make like this but it didnt work at all...
pls if someone can help me with that i would be very appreciated !
Higor
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Re: TArray Indexing Order(Question) ?

Post by Higor »

Why'd you do that?
FName is nothing more than a typecasted INT, and except for hardcoded names they're all allocated dynamically in table with name entries.
Loading names using 'INT' leads to nothing.

You need to save the name table first, into a memory block prefferably.
Enumerate like this all names you're going to write:

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TArray<FName> NameTable;
Loop all names you're going to use and add them to the table.
Also do:

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INT NameBytes = 0;
for ( INT i=0 ; i<NameTable.Num() ; i++ )
    NameBytes += appStrlen(*NameTable(i));
void* NameTable = appMalloc( NameBytes + NameTable.Num() * 5); //5 bytes: 4 for flags (DWORD), 1 for ending char
BYTE* Pos = (BYTE*)NameTable;
for ( INT i=0 ; i<NameTable.Num() ; i++ )
{
    *((DWORD*)Pos) = NameTable(i).GetFlags();
    Pos += 4;
    for ( INT j=0 ; j<63 && (*NameTable(i))[j] ; j++ )
        *Pos++ = (*NameTable(i))[j];
    *Pos++ = 0; //Ending char
}
Now you have a fully computed name table, and I didn't even look at the game's Linker code, all using public sources, stuff you understand once you see the wiki.
bolvai
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Re: TArray Indexing Order(Question) ?

Post by bolvai »

Ehm And how do i write FCompact index anyway ?
im using WriteFile, without FArchive stuff ?
can you help me in making this , into a macro over Int value !
pls
Higor
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Re: TArray Indexing Order(Question) ?

Post by Higor »

Isn't FCompactIndex a CORE_API export?
It's available in there up to some UE2 builds, and apparently it's been deprecated in UE3.
First things first, figure out if the game you're targeting has and FCompactIndex related symbols (Core.dll)
If it does, see if this operator is indeed an export in Core.dll, if it is, then you don't need to rewrite it.

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//
// Class for serializing objects in a compactly, mapping small values
// to fewer bytes.
//
class CORE_API FCompactIndex
{
public:
	INT Value;
	CORE_API friend FArchive& operator<<( FArchive& Ar, FCompactIndex& I );
};
bolvai
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Re: TArray Indexing Order(Question) ?

Post by bolvai »

You dont get me - i have this function serializer, I need to transform it to an simple macro without FArchive need, so i can use WriteFile(Fcompactint), i tried to do this but it only return a 1 byte, because i dont know how to sort all of the bytes with bit shit operator << ! Can you help me in this please ?
Higor
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Re: TArray Indexing Order(Question) ?

Post by Higor »

Duh

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class FArchiveProxy : public FArchive //Use this to use FArchive functions to write into memory instead of file, very useful because '<<' operators only want FArchive types
{
public:
    BYTE* WriteTo;
    //Use a constructor if you wish
    void /*UBOOL, WHATEVER*/ Serialize(...) //Not gonna look at the headers, correct this if you wish
    {
         //Copy memory to WriteTo, advance WriteTo pointer to new position
         //Heck, you can write the entire name table and other stuff in this memory... just make sure you allocate it first
    }
    //Destroy this once you finish using it.
}
bolvai
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Re: TArray Indexing Order(Question) ?

Post by bolvai »

Higor wrote:Duh

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class FArchiveProxy : public FArchive //Use this to use FArchive functions to write into memory instead of file, very useful because '<<' operators only want FArchive types
{
public:
    BYTE* WriteTo;
    //Use a constructor if you wish
    void /*UBOOL, WHATEVER*/ Serialize(...) //Not gonna look at the headers, correct this if you wish
    {
         //Copy memory to WriteTo, advance WriteTo pointer to new position
         //Heck, you can write the entire name table and other stuff in this memory... just make sure you allocate it first
    }
    //Destroy this once you finish using it.
}
But is it possible to not use FArchive at all, just to transform that Fcompact into Macro ? or it is too hard ?
bolvai
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Re: TArray Indexing Order(Question) ?

Post by bolvai »

And there is a problem storing BYTE's - here idk for what reason but if i use Tarray<T> Arr; or even simple STD:array, with add or push_back - it allways give me critical error when im ingame, only thing that works is std::vector, but its not perfect cause its predefined in size but findex its dynamic sized, do you know what can be done here ?
Higor
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Re: TArray Indexing Order(Question) ?

Post by Higor »

Take a look, that (BYTE*) thing is a pointer, you're letting the game write those for you.
I think you can properly figure out how many bytes the FArchive wrote by inspecting Pos() or something else in there...

Dynamic arrays are cool, provided you know how they work.
As long as you can, stick to UE structures and headers (even if you need some other UE2 game headers for this), and no platform specific stuff.
BTW if you know how much space will be using before the storage, don't even use TArray, go straight appMalloc


EDIT:

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INT RawData[32]; //128 bytes of something
FArchiveProxy ByteWriter(...); //Allocate it in the stack, not important anyways
ByteWriter->WriteTo = (BYTE*)RawData; //You can typecast any kind of pointer here

ByteWriter->Serialize( stuff, stuff's size); //Writing generic data
ByteWriter->Serialize( stuff, stuff's size); //Writing generic data
FCompactIndex Blah = Something; //I want to compress this, AND see how much bytes it took
BYTE* OldWriteTo = ByteWriter->WriteTo;
ByteWriter << Blah;
INT CompressedSize = (INT)ByteWriter->WriteTo- (INT)OldWriteTo;
//This code won't crash as long as you don't exceed your 128 byte buffer
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