Crate fastnbt[−][src]
Expand description
fastnbt aims for fast deserializing of NBT data from Minecraft: Java Edition. This format is used by the game to store various things, such as the world data and player inventories.
- For documentation and examples of serde deserialization, see
de
. - For a
serde_json
-likeValue
type seeValue
. - For NBT array types see
ByteArray
,IntArray
, andLongArray
. - For ‘zero-copy’ NBT array types see
borrow
.
Both this and related crates are under one fastnbt Github repository
[dependencies]
fastnbt = "1"
Byte, Int and Long array types
There are three array types in NBT. To capture these, use ByteArray
,
IntArray
, and LongArray
. These NBT types do not deserialize straight
into serde sequences like Vec
in order to preserve the information from
the original NBT. Without these types, it is not possible to tell if some
data came from a NBT List or an NBT Array.
Use these in your own data structures. They all implement
Deref
for dereferencing into the underlying Vec
.
For versions that borrow their data, see borrow
. For more information
about deserialization see de
.
An example of deserializing a section of a chunk:
use fastnbt::LongArray;
use serde::Deserialize;
#[derive(Deserialize)]
#[serde(rename_all = "PascalCase")]
pub struct Section {
pub block_states: Option<LongArray>,
pub y: i8,
}
let buf: &[u8] = unimplemented!("get a buffer from somewhere");
let section: Section = fastnbt::de::from_bytes(buf).unwrap();
let states = section.block_states.unwrap();
for long in states.iter() {
// do something
}
Example: Player inventory
This example demonstrates printing out a players inventory and ender chest contents from the player dat files found in worlds.
Here we
- use serde’s renaming attributes to have rustfmt conformant field names,
- use lifetimes to save on some string allocations (see
de
for more info), and - use the
Value
type to deserialize a field we don’t know the exact structure of.
use std::borrow::Cow;
use fastnbt::error::Result;
use fastnbt::{de::from_bytes, Value};
use flate2::read::GzDecoder;
use serde::Deserialize;
use std::io::Read;
#[derive(Deserialize, Debug)]
#[serde(rename_all = "PascalCase")]
struct PlayerDat<'a> {
data_version: i32,
#[serde(borrow)]
inventory: Vec<InventorySlot<'a>>,
ender_items: Vec<InventorySlot<'a>>,
}
#[derive(Deserialize, Debug)]
struct InventorySlot<'a> {
// We typically avoid allocating a string here.
// See `fastnbt::de` docs for more info.
id: Cow<'a, str>,
// Also get the less structured properties of the object.
tag: Option<Value>,
// We need to rename fields a lot.
#[serde(rename = "Count")]
count: i8,
}
let args: Vec<_> = std::env::args().skip(1).collect();
let file = std::fs::File::open(args[0].clone()).unwrap();
// Player dat files are compressed with GZip.
let mut decoder = GzDecoder::new(file);
let mut data = vec![];
decoder.read_to_end(&mut data).unwrap();
let player: Result<PlayerDat> = from_bytes(data.as_slice());
println!("{:#?}", player);
Read
based parser
A lower level parser also exists in the stream
module that only requires
the Read
trait on the input. This parser however doesn’t support
deserializing to Rust objects directly.
Modules
This module contains types enabling ‘zero-copy’ capture of the array NBT types. These types retain a reference to the input data when deserializing, meaning the input has to live as long as the deserialized object. This can be hard to manage, but offers potential performance improvements. Measure! Usually the dominating factor in deserialization is decompressing the NBT data.
This module contains a serde deserializer. It can do most of the things you would expect of a typical serde deserializer, such as deserializing into:
Contains the Error and Result type used by the deserializer.
Allows streaming of NBT data without prior knowledge of the structure.
Structs
Enums
An NBT tag. This does not carry the value or the name of the data.
Value is a complete NBT value. It owns its data. Compounds and Lists are resursively deserialized. This type takes care to preserve all the information from the original NBT, with the exception of the name of the root compound (which is usually the empty string).