HELP: minetest .sqlite format

[dgm5555]

I want to create a converter from minecraft worlds to minetest. I have found python code which can extract information from minecraft anvil and mcregion format files (which is way above my head, but I figure can be used with some very basic modification - see another post starting to break this down - https://forum.minetest.net/viewtopic.php?f=5&t=11146.
I've read the minetest file format page: https://github.com/minetest/minetest/blob/master/doc/mapformat.txt

And I have no idea what it means...
not even the faintest idea of how to even start generating the header stuff...
:'(
Can anyone help? Essentially I want to develop python code which can create a 'naked' minetest map.sqlite file which just needs the node information from minecraft injected into it.

[rubenwardy]

Use the sqlite library in python and create the tables using SQL statements. There is a CREATE TABLE that you need to run in the file format file.

The blob is just binary data, one value after another.

[dgm5555]

Ha, that much even I get. It's the magicHappens section that I really don't understand (but I am figuring out).

Soooo...
In the beginning there was a table and that table was called "blocks"
And lo, inside blocks were contained two columns called 'pos' and 'data'
And it was a good and sensible(ish) structure
(the bit that isn't sensible is that most builders call the individual building blocks of minetest either blocks, nodes, or sometimes voxels
However 'block' also refer to groups of nodes (also called mapBlocks, sectors or chunks)
mapBlocks are chunks of 16x16x16 nodes)

And pos (an int) was the primary index key
https://github.com/minetest/minetest/blob/master/src/database.cpp

To get pos if you know the x,y,z coordinates of a chunk use:-

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Code: Select all

p = {X=xCoord, Y=yCoord, Z=zCoord}

def getBlockAsInteger(p):
    return int64(p.Z*16777216 + p.Y*4096 + p.X)

def int64(u):
    while u >= 2**63:
        u -= 2**64
    while u <= -2**63:
        u += 2**64
    return u


to get x,y,z if you know the pos (="go the other way")

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def getIntegerAsBlock(i):
    x = unsignedToSigned(i % 4096, 2048)
    i = int((i - x) / 4096)
    y = unsignedToSigned(i % 4096, 2048)
    i = int((i - y) / 4096)
    z = unsignedToSigned(i % 4096, 2048)
    return x,y,z

def unsignedToSigned(i, max_positive):
    if i < max_positive:
        return i
    else:
        return i - 2*max_positive


data (a blob) contains everything else. a blob is a variable sized binary format data storage unit, which stores data about a 16x16x16 chunk of nodes.
https://github.com/minetest/minetest/blob/master/src/mapblock.cpp

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MapBlock:
The following assumes map format version >= 24:
u8 refers to an 8-bit byte, 0x refers to a bit within the byte
u16 is a 16 bit byte

u8 version
u8 flags
- 0x01: is_underground
- 0x02: day_night_differs
- 0x04: lighting_expired
- 0x08: generated
u8 content_width    # Number of bytes in the content (param0) fields of nodes
u8 params_width     # Number of bytes used for parameters per node

Now comes the node data (which is zlib-compressed)
- The location of a node in each of those arrays is (z*16*16 + y*16 + x).
u16[4096]: param0   # The content id of a node
u8[4096]: param1    # use varies with node type
u8[4096]: param2    # use varies with node type

Now comes meta-data (which is zlib-compressed)
u16 version         # (always=1)
u16 count           # of metadata
foreach count:
    u16 position (p.Z*MAP_BLOCKSIZE*MAP_BLOCKSIZE + p.Y*MAP_BLOCKSIZE + p.X)
    u16 type_id
    u16 content_size
    u8[content_size]    # array containing the actual metadata
   
Then comes more bits and bobs (timers,timestamp, etc)
...
[EOF]   terminates the blob

To put it in or get it out call
magicHappensIn(allTheLittleRandomBitsOfData)
return blob

magicHappensOut(blob)
return allTheLittleRandomBitsOfData

magicHappens() still needs some consideration. However the source code which serialises the data is in https://github.com/minetest/minetest/blob/master/src/mapblock.cpp
So I just have to figure this out...

[lag01]

I got one step further in this matter and split this "magic blob" in little smaller parts. But it is still far from manipulating individual nodes and especially their metadata.
viewtopic.php?f=14&t=10333

[ptvirgo]

Did you manage to sort out the nodes? I'm also trying to convert the block data into something a person could actually read; interpreting the bytes from the available documentation is proving a challenge.