Struct RawValue

pub struct RawValue { /* private fields */ }

Reference to a range of bytes encompassing a single valid JSON value in the input data.

A RawValue can be used to defer parsing parts of a payload until later, or to avoid parsing it at all in the case that part of the payload just needs to be transferred verbatim into a different output object.

When serializing, a value of this type will retain its original formatting and will not be minified or pretty-printed.

Note

RawValue is only available if serde_json is built with the "raw_value" feature.

[dependencies]
serde_json = { version = "1.0", features = ["raw_value"] }

Example

use serde::{Deserialize, Serialize};
use serde_json::{Result, value::RawValue};

#[derive(Deserialize)]
struct Input<'a> {
    code: u32,
    #[serde(borrow)]
    payload: &'a RawValue,
}

#[derive(Serialize)]
struct Output<'a> {
    info: (u32, &'a RawValue),
}

// Efficiently rearrange JSON input containing separate "code" and "payload"
// keys into a single "info" key holding an array of code and payload.
//
// This could be done equivalently using serde_json::Value as the type for
// payload, but &RawValue will perform better because it does not require
// memory allocation. The correct range of bytes is borrowed from the input
// data and pasted verbatim into the output.
fn rearrange(input: &str) -> Result<String> {
    let input: Input = serde_json::from_str(input)?;

    let output = Output {
        info: (input.code, input.payload),
    };

    serde_json::to_string(&output)
}

fn main() -> Result<()> {
    let out = rearrange(r#" {"code": 200, "payload": {}} "#)?;

    assert_eq!(out, r#"{"info":[200,{}]}"#);

    Ok(())
}

Ownership

The typical usage of RawValue will be in the borrowed form:

#[derive(Deserialize)]
struct SomeStruct<'a> {
    #[serde(borrow)]
    raw_value: &'a RawValue,
}

The borrowed form is suitable when deserializing through serde_json::from_str and serde_json::from_slice which support borrowing from the input data without memory allocation.

When deserializing through serde_json::from_reader you will need to use the boxed form of RawValue instead. This is almost as efficient but involves buffering the raw value from the I/O stream into memory.

#[derive(Deserialize)]
struct SomeStruct {
    raw_value: Box<RawValue>,
}

Implementations

impl RawValue

pub fn from_string(json: String) -> Result<Box<Self>, Error>

Convert an owned String of JSON data to an owned RawValue.

This function is equivalent to serde_json::from_str::<Box<RawValue>> except that we avoid an allocation and memcpy if both of the following are true:

• the input has no leading or trailing whitespace, and
• the input has capacity equal to its length.

pub fn get(&self) -> &str

Access the JSON text underlying a raw value.

Example

use serde::Deserialize;
use serde_json::{Result, value::RawValue};

#[derive(Deserialize)]
struct Response<'a> {
    code: u32,
    #[serde(borrow)]
    payload: &'a RawValue,
}

fn process(input: &str) -> Result<()> {
    let response: Response = serde_json::from_str(input)?;

    let payload = response.payload.get();
    if payload.starts_with('{') {
        // handle a payload which is a JSON map
    } else {
        // handle any other type
    }

    Ok(())
}

fn main() -> Result<()> {
    process(r#" {"code": 200, "payload": {}} "#)?;
    Ok(())
}

Trait Implementations

impl Clone for Box<RawValue>

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for RawValue

fn fmt(&self, formatter: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Box<RawValue>

fn default() -> Self

Returns the “default value” for a type.

impl<'de: 'a, 'a> Deserialize<'de> for &'a RawValue

fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl<'de> Deserialize<'de> for Box<RawValue>

fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl<'de> Deserializer<'de> for &'de RawValue

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, Error>

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, Error>

where V: Visitor<'de>,

Hint that the Deserialize type is expecting a bool value.

fn deserialize_i8<V>(self, visitor: V) -> Result<V::Value, Error>

where V: Visitor<'de>,

Hint that the Deserialize type is expecting an i8 value.

fn deserialize_i16<V>(self, visitor: V) -> Result<V::Value, Error>

where V: Visitor<'de>,

Hint that the Deserialize type is expecting an i16 value.

fn deserialize_i32<V>(self, visitor: V) -> Result<V::Value, Error>

where V: Visitor<'de>,

Hint that the Deserialize type is expecting an i32 value.

fn deserialize_i64<V>(self, visitor: V) -> Result<V::Value, Error>

where V: Visitor<'de>,

Hint that the Deserialize type is expecting an i64 value.

fn deserialize_i128<V>(self, visitor: V) -> Result<V::Value, Error>

where V: Visitor<'de>,

Hint that the Deserialize type is expecting an i128 value.

fn deserialize_u8<V>(self, visitor: V) -> Result<V::Value, Error>

where V: Visitor<'de>,

Hint that the Deserialize type is expecting a u8 value.

fn deserialize_u16<V>(self, visitor: V) -> Result<V::Value, Error>

where V: Visitor<'de>,

Hint that the Deserialize type is expecting a u16 value.

fn deserialize_u32<V>(self, visitor: V) -> Result<V::Value, Error>

where V: Visitor<'de>,

Hint that the Deserialize type is expecting a u32 value.

fn deserialize_u64<V>(self, visitor: V) -> Result<V::Value, Error>

where V: Visitor<'de>,

Hint that the Deserialize type is expecting a u64 value.

fn deserialize_u128<V>(self, visitor: V) -> Result<V::Value, Error>

where V: Visitor<'de>,

Hint that the Deserialize type is expecting an u128 value.

fn deserialize_f32<V>(self, visitor: V) -> Result<V::Value, Error>

where V: Visitor<'de>,

Hint that the Deserialize type is expecting a f32 value.

fn deserialize_f64<V>(self, visitor: V) -> Result<V::Value, Error>

where V: Visitor<'de>,

Hint that the Deserialize type is expecting a f64 value.

fn deserialize_char<V>(self, visitor: V) -> Result<V::Value, Error>

where V: Visitor<'de>,

Hint that the Deserialize type is expecting a char value.

fn deserialize_str<V>(self, visitor: V) -> Result<V::Value, Error>

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, Error>

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_bytes<V>(self, visitor: V) -> Result<V::Value, Error>

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_byte_buf<V>(self, visitor: V) -> Result<V::Value, Error>

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_option<V>(self, visitor: V) -> Result<V::Value, Error>

where V: Visitor<'de>,

Hint that the Deserialize type is expecting an optional value.

fn deserialize_unit<V>(self, visitor: V) -> Result<V::Value, Error>

where V: Visitor<'de>,

Hint that the Deserialize type is expecting a unit value.

fn deserialize_unit_struct<V>( self, name: &'static str, visitor: V, ) -> Result<V::Value, Error>

where V: Visitor<'de>,

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

fn deserialize_newtype_struct<V>( self, name: &'static str, visitor: V, ) -> Result<V::Value, Error>

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, Error>

where V: Visitor<'de>,

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

fn deserialize_tuple<V>(self, len: usize, visitor: V) -> Result<V::Value, Error>

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, Error>

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, Error>

where V: Visitor<'de>,

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

fn deserialize_struct<V>( self, name: &'static str, fields: &'static [&'static str], visitor: V, ) -> Result<V::Value, Error>

where V: Visitor<'de>,

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

fn deserialize_enum<V>( self, name: &'static str, variants: &'static [&'static str], visitor: V, ) -> Result<V::Value, Error>

where V: Visitor<'de>,

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

fn deserialize_identifier<V>(self, visitor: V) -> Result<V::Value, Error>

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_ignored_any<V>(self, visitor: V) -> Result<V::Value, Error>

where V: Visitor<'de>,

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

fn is_human_readable(&self) -> bool

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

impl Display for RawValue

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de> IntoDeserializer<'de, Error> for &'de RawValue

type Deserializer = &'de RawValue

The type of the deserializer being converted into.

fn into_deserializer(self) -> Self::Deserializer

Convert this value into a deserializer.

impl Serialize for RawValue

fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.

impl ToOwned for RawValue

type Owned = Box<RawValue>

The resulting type after obtaining ownership.

fn to_owned(&self) -> Self::Owned

Creates owned data from borrowed data, usually by cloning.

fn clone_into(&self, target: &mut Self::Owned)

Uses borrowed data to replace owned data, usually by cloning.