1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243
use lib::*;
use de::{
Deserialize, Deserializer, EnumAccess, Error, MapAccess, SeqAccess, VariantAccess, Visitor,
};
/// An efficient way of discarding data from a deserializer.
///
/// Think of this like `serde_json::Value` in that it can be deserialized from
/// any type, except that it does not store any information about the data that
/// gets deserialized.
///
/// ```edition2018
/// use std::fmt;
/// use std::marker::PhantomData;
///
/// use serde::de::{
/// self, Deserialize, DeserializeSeed, Deserializer, IgnoredAny, SeqAccess, Visitor,
/// };
///
/// /// A seed that can be used to deserialize only the `n`th element of a sequence
/// /// while efficiently discarding elements of any type before or after index `n`.
/// ///
/// /// For example to deserialize only the element at index 3:
/// ///
/// /// ```
/// /// NthElement::new(3).deserialize(deserializer)
/// /// ```
/// pub struct NthElement<T> {
/// n: usize,
/// marker: PhantomData<T>,
/// }
///
/// impl<T> NthElement<T> {
/// pub fn new(n: usize) -> Self {
/// NthElement {
/// n: n,
/// marker: PhantomData,
/// }
/// }
/// }
///
/// impl<'de, T> Visitor<'de> for NthElement<T>
/// where
/// T: Deserialize<'de>,
/// {
/// type Value = T;
///
/// fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
/// write!(
/// formatter,
/// "a sequence in which we care about element {}",
/// self.n
/// )
/// }
///
/// fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
/// where
/// A: SeqAccess<'de>,
/// {
/// // Skip over the first `n` elements.
/// for i in 0..self.n {
/// // It is an error if the sequence ends before we get to element `n`.
/// if seq.next_element::<IgnoredAny>()?.is_none() {
/// return Err(de::Error::invalid_length(i, &self));
/// }
/// }
///
/// // Deserialize the one we care about.
/// let nth = match seq.next_element()? {
/// Some(nth) => nth,
/// None => {
/// return Err(de::Error::invalid_length(self.n, &self));
/// }
/// };
///
/// // Skip over any remaining elements in the sequence after `n`.
/// while let Some(IgnoredAny) = seq.next_element()? {
/// // ignore
/// }
///
/// Ok(nth)
/// }
/// }
///
/// impl<'de, T> DeserializeSeed<'de> for NthElement<T>
/// where
/// T: Deserialize<'de>,
/// {
/// type Value = T;
///
/// fn deserialize<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
/// where
/// D: Deserializer<'de>,
/// {
/// deserializer.deserialize_seq(self)
/// }
/// }
///
/// # fn example<'de, D>(deserializer: D) -> Result<(), D::Error>
/// # where
/// # D: Deserializer<'de>,
/// # {
/// // Deserialize only the sequence element at index 3 from this deserializer.
/// // The element at index 3 is required to be a string. Elements before and
/// // after index 3 are allowed to be of any type.
/// let s: String = NthElement::new(3).deserialize(deserializer)?;
/// # Ok(())
/// # }
/// ```
#[derive(Copy, Clone, Debug, Default)]
pub struct IgnoredAny;
impl<'de> Visitor<'de> for IgnoredAny {
type Value = IgnoredAny;
fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
formatter.write_str("anything at all")
}
#[inline]
fn visit_bool<E>(self, x: bool) -> Result<Self::Value, E> {
let _ = x;
Ok(IgnoredAny)
}
#[inline]
fn visit_i64<E>(self, x: i64) -> Result<Self::Value, E> {
let _ = x;
Ok(IgnoredAny)
}
serde_if_integer128! {
#[inline]
fn visit_i128<E>(self, x: i128) -> Result<Self::Value, E> {
let _ = x;
Ok(IgnoredAny)
}
}
#[inline]
fn visit_u64<E>(self, x: u64) -> Result<Self::Value, E> {
let _ = x;
Ok(IgnoredAny)
}
serde_if_integer128! {
#[inline]
fn visit_u128<E>(self, x: u128) -> Result<Self::Value, E> {
let _ = x;
Ok(IgnoredAny)
}
}
#[inline]
fn visit_f64<E>(self, x: f64) -> Result<Self::Value, E> {
let _ = x;
Ok(IgnoredAny)
}
#[inline]
fn visit_str<E>(self, s: &str) -> Result<Self::Value, E>
where
E: Error,
{
let _ = s;
Ok(IgnoredAny)
}
#[inline]
fn visit_none<E>(self) -> Result<Self::Value, E> {
Ok(IgnoredAny)
}
#[inline]
fn visit_some<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
where
D: Deserializer<'de>,
{
IgnoredAny::deserialize(deserializer)
}
#[inline]
fn visit_newtype_struct<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
where
D: Deserializer<'de>,
{
IgnoredAny::deserialize(deserializer)
}
#[inline]
fn visit_unit<E>(self) -> Result<Self::Value, E> {
Ok(IgnoredAny)
}
#[inline]
fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
where
A: SeqAccess<'de>,
{
while let Some(IgnoredAny) = try!(seq.next_element()) {
// Gobble
}
Ok(IgnoredAny)
}
#[inline]
fn visit_map<A>(self, mut map: A) -> Result<Self::Value, A::Error>
where
A: MapAccess<'de>,
{
while let Some((IgnoredAny, IgnoredAny)) = try!(map.next_entry()) {
// Gobble
}
Ok(IgnoredAny)
}
#[inline]
fn visit_bytes<E>(self, bytes: &[u8]) -> Result<Self::Value, E>
where
E: Error,
{
let _ = bytes;
Ok(IgnoredAny)
}
fn visit_enum<A>(self, data: A) -> Result<Self::Value, A::Error>
where
A: EnumAccess<'de>,
{
data.variant::<IgnoredAny>()?.1.newtype_variant()
}
}
impl<'de> Deserialize<'de> for IgnoredAny {
#[inline]
fn deserialize<D>(deserializer: D) -> Result<IgnoredAny, D::Error>
where
D: Deserializer<'de>,
{
deserializer.deserialize_ignored_any(IgnoredAny)
}
}