[][src]Struct serde_json::value::RawValue

#[repr(C)]
pub struct RawValue { /* fields omitted */ }

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

This code runs with edition 2018
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:

This code runs with edition 2018
#[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.

This code runs with edition 2018
#[derive(Deserialize)]
struct SomeStruct {
    raw_value: Box<RawValue>,
}

Methods

impl RawValue[src]

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

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[src]

Access the JSON text underlying a raw value.

Example

This code runs with edition 2018
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 ToOwned for RawValue[src]

type Owned = Box<RawValue>

The resulting type after obtaining ownership.

impl Debug for RawValue[src]

impl Display for RawValue[src]

impl Serialize for RawValue[src]

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

Auto Trait Implementations

Blanket Implementations

impl<T> ToOwned for T where
    T: Clone
[src]

type Owned = T

The resulting type after obtaining ownership.

impl<T> ToString for T where
    T: Display + ?Sized
[src]

impl<T> Borrow<T> for T where
    T: ?Sized
[src]

impl<T> BorrowMut<T> for T where
    T: ?Sized
[src]

impl<T> Any for T where
    T: 'static + ?Sized
[src]