Struct fastnbt::de::Deserializer

pub struct Deserializer<'de> { /* fields omitted */ }

Deserializer for getting a T from some NBT data. Quite often you will need to rename fields using serde, as most Minecraft NBT data has inconsistent naming. The examples below show this with the rename_all attribute. See serdes other attributes for more.

You can take advantage of the lifetime of the input data to save allocations for things like strings. You can also deserialize any Array or List of primitive type as &'a [u8] to avoid allocating this data. See example below.

When deserializing integral types, the values are range checked to prevent overflow from occurring. If an overflow does occur you will get a Error::IntegralOutOfRange error.

Example of deserializing player.dat

use serde::Deserialize;

#[derive(Deserialize, Debug)]
#[serde(rename_all = "PascalCase")]
struct PlayerDat {
    data_version: i32,
    inventory: Vec<InventorySlot>,
    ender_items: Vec<InventorySlot>,
}

#[derive(Deserialize, Debug)]
struct InventorySlot {
    id: String,
}

Examples of avoiding allocation

We can easily avoid allocations of Strings using &'a str where 'a is the lifetime of the input data.

use serde::Deserialize;
#[derive(Deserialize, Debug)]
struct InventorySlot<'a> {
    id: &'a str, // we avoid allocating a string here.
}

Here we're avoiding allocating memory for the various heightmaps found in chunk data. The PackedBits type is used as a wrapper for the way Minecraft's Anvil format packs various lists of numbers.

use fastnbt::anvil::PackedBits;
use serde::Deserialize;


#[derive(Deserialize, Debug)]
#[serde(rename_all = "SCREAMING_SNAKE_CASE")]
pub struct Heightmaps<'a> {
    #[serde(borrow)]
    pub motion_blocking: Option<PackedBits<'a>>,
    pub motion_blocking_no_leaves: Option<PackedBits<'a>>,
    pub ocean_floor: Option<PackedBits<'a>>,
    pub world_surface: Option<PackedBits<'a>>,

    #[serde(skip)]
    unpacked_motion_blocking: Option<Vec<u16>>,
}

Example from region file

use fastnbt::anvil::{Chunk, Region};
use fastnbt::de::from_bytes;

fn main() {
    let args: Vec<_> = std::env::args().skip(1).collect();
    let file = std::fs::File::open(args[0].clone()).unwrap();

    let mut region = Region::new(file);
    let data = region.load_chunk(0, 0).unwrap();

    let chunk: Chunk = from_bytes(data.as_slice()).unwrap();

    println!("{:?}", chunk);
}

Implementations

impl<'de> Deserializer<'de>

pub fn from_bytes(input: &'de [u8]) -> Self

Trait Implementations

impl<'de, 'a> Deserializer<'de> for &'a mut Deserializer<'de>

type Error = Error

The error type that can be returned if some error occurs during deserialization.

fn deserialize_any<V>(self, _visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Require the Deserializer to figure out how to drive the visitor based on what data type is in the input.

fn deserialize_bool<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting a bool value.

fn deserialize_struct<V>(
    self,
    _name: &'static str,
    _fields: &'static [&'static str],
    visitor: V
) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting a struct with a particular name and fields.

fn deserialize_identifier<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting the name of a struct field or the discriminant of an enum variant.

fn deserialize_byte_buf<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting a byte array and would benefit from taking ownership of buffered data owned by the Deserializer.

fn deserialize_bytes<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting a byte array and does not benefit from taking ownership of buffered data owned by the Deserializer.

fn deserialize_char<V>(self, _: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting a char value.

fn deserialize_enum<V>(
    self,
    _name: &'static str,
    _variants: &'static [&'static str],
    visitor: V
) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting an enum value with a particular name and possible variants.

fn deserialize_f32<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting a f32 value.

fn deserialize_f64<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting a f64 value.

fn deserialize_u8<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting a u8 value.

fn deserialize_i8<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting an i8 value.

fn deserialize_i16<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting an i16 value.

fn deserialize_i32<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting an i32 value.

fn deserialize_i64<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting an i64 value.

fn deserialize_u16<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting a u16 value.

fn deserialize_u32<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting a u32 value.

fn deserialize_u64<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting a u64 value.

fn deserialize_str<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting a string value and does not benefit from taking ownership of buffered data owned by the Deserializer.

fn deserialize_string<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting a string value and would benefit from taking ownership of buffered data owned by the Deserializer.

fn deserialize_option<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting an optional value.

fn deserialize_unit<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting a unit value.

fn deserialize_unit_struct<V>(self, _: &'static str, _: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting a unit struct with a particular name.

fn deserialize_newtype_struct<V>(
    self,
    _: &'static str,
    visitor: V
) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting a newtype struct with a particular name.

fn deserialize_seq<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting a sequence of values.

fn deserialize_tuple<V>(self, _: usize, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting a sequence of values and knows how many values there are without looking at the serialized data.

fn deserialize_tuple_struct<V>(
    self,
    _name: &'static str,
    _len: usize,
    _visitor: V
) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting a tuple struct with a particular name and number of fields.

fn deserialize_map<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting a map of key-value pairs.

fn deserialize_ignored_any<V>(self, visitor: V) -> Result<V::Value> where
    V: Visitor<'de>, 

Hint that the Deserialize type needs to deserialize a value whose type doesn't matter because it is ignored.

fn deserialize_i128<V>(
    self,
    visitor: V
) -> Result<<V as Visitor<'de>>::Value, Self::Error> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting an i128 value.

fn deserialize_u128<V>(
    self,
    visitor: V
) -> Result<<V as Visitor<'de>>::Value, Self::Error> where
    V: Visitor<'de>, 

Hint that the Deserialize type is expecting an u128 value.

fn is_human_readable(&self) -> bool

Determine whether Deserialize implementations should expect to deserialize their human-readable form.