fastnbt 2.0.2

Serde deserializer for Minecraft's NBT format
Documentation 
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use serde::de;
use serde::de::value::BorrowedBytesDeserializer;
use serde::de::value::BorrowedStrDeserializer;

use crate::de::Deserializer;
use crate::error::{Error, Result};
use crate::BYTE_ARRAY_TOKEN;
use crate::INT_ARRAY_TOKEN;
use crate::LONG_ARRAY_TOKEN;

enum State {
    Unread,
    Read,
}

pub(crate) struct ArrayWrapperAccess<'a, 'de> {
    de: &'a mut Deserializer<'de>,
    token: &'static str,
    bytes_size: usize,
    state: State,
}

impl<'a, 'de> ArrayWrapperAccess<'a, 'de> {
    pub(crate) fn bytes(de: &'a mut Deserializer<'de>, size: usize) -> Result<Self> {
        Ok(Self {
            de,
            bytes_size: size
                .checked_mul(1)
                .ok_or_else(|| Error::bespoke("nbt array too large".to_string()))?,
            token: BYTE_ARRAY_TOKEN,
            state: State::Unread,
        })
    }

    pub(crate) fn ints(de: &'a mut Deserializer<'de>, size: usize) -> Result<Self> {
        Ok(Self {
            de,
            bytes_size: size
                .checked_mul(4)
                .ok_or_else(|| Error::bespoke("nbt array too large".to_string()))?,
            token: INT_ARRAY_TOKEN,
            state: State::Unread,
        })
    }

    pub(crate) fn longs(de: &'a mut Deserializer<'de>, size: usize) -> Result<Self> {
        Ok(Self {
            de,
            bytes_size: size
                .checked_mul(8)
                .ok_or_else(|| Error::bespoke("nbt array too large".to_string()))?,
            token: LONG_ARRAY_TOKEN,
            state: State::Unread,
        })
    }
}

impl<'a, 'de> de::MapAccess<'de> for ArrayWrapperAccess<'a, 'de> {
    type Error = Error;

    fn next_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>>
    where
        K: de::DeserializeSeed<'de>,
    {
        if let State::Unread = self.state {
            self.state = State::Read;
            seed.deserialize(BorrowedStrDeserializer::new(self.token))
                .map(Some)
        } else {
            Ok(None)
        }
    }

    fn next_value_seed<V>(&mut self, seed: V) -> Result<V::Value>
    where
        V: de::DeserializeSeed<'de>,
    {
        let data = self.de.input.consume_bytes_usize(self.bytes_size)?;
        let dz = BorrowedBytesDeserializer::new(data);
        seed.deserialize(dz)
    }
}