blob: a6b64108e2600663eaf67ea79359dfbd443a76de [file] [log] [blame]
use std::fmt::{self, Debug, Display};
use std::mem;
use serde::de::value::BorrowedStrDeserializer;
use serde::de::{
self, Deserialize, DeserializeSeed, Deserializer, IntoDeserializer, MapAccess, Unexpected,
Visitor,
};
use serde::ser::{Serialize, SerializeStruct, Serializer};
use error::Error;
/// 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.
///
/// # Example
///
/// ```
/// #[macro_use]
/// extern crate serde_derive;
/// extern crate serde_json;
///
/// 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 netter 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:
///
/// ```
/// # #[macro_use]
/// # extern crate serde_derive;
/// # extern crate serde_json;
/// #
/// # use serde_json::value::RawValue;
/// #
/// #[derive(Deserialize)]
/// struct SomeStruct<'a> {
/// #[serde(borrow)]
/// raw_value: &'a RawValue,
/// }
/// #
/// # fn main() {}
/// ```
///
/// 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.
///
/// [`serde_json::from_str`]: ../fn.from_str.html
/// [`serde_json::from_slice`]: ../fn.from_slice.html
/// [`serde_json::from_reader`]: ../fn.from_reader.html
///
/// ```
/// # #[macro_use]
/// # extern crate serde_derive;
/// # extern crate serde_json;
/// #
/// # use serde_json::value::RawValue;
/// #
/// #[derive(Deserialize)]
/// struct SomeStruct {
/// raw_value: Box<RawValue>,
/// }
/// #
/// # fn main() {}
/// ```
///
/// # Note
///
/// `RawValue` is only available if serde\_json is built with the `"raw_value"`
/// feature.
///
/// ```toml
/// [dependencies]
/// serde_json = { version = "1.0", features = ["raw_value"] }
/// ```
#[repr(C)]
pub struct RawValue {
json: str,
}
impl RawValue {
fn from_borrowed(json: &str) -> &Self {
unsafe { mem::transmute::<&str, &RawValue>(json) }
}
fn from_owned(json: Box<str>) -> Box<Self> {
unsafe { mem::transmute::<Box<str>, Box<RawValue>>(json) }
}
}
impl Clone for Box<RawValue> {
fn clone(&self) -> Self {
(**self).to_owned()
}
}
impl ToOwned for RawValue {
type Owned = Box<RawValue>;
fn to_owned(&self) -> Self::Owned {
RawValue::from_owned(self.json.to_owned().into_boxed_str())
}
}
impl Default for Box<RawValue> {
fn default() -> Self {
RawValue::from_borrowed("null").to_owned()
}
}
impl Debug for RawValue {
fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
formatter
.debug_tuple("RawValue")
.field(&format_args!("{}", &self.json))
.finish()
}
}
impl Display for RawValue {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.write_str(&self.json)
}
}
impl RawValue {
/// 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 from_string(json: String) -> Result<Box<Self>, Error> {
{
let borrowed = ::from_str::<&Self>(&json)?;
if borrowed.json.len() < json.len() {
return Ok(borrowed.to_owned());
}
}
Ok(Self::from_owned(json.into_boxed_str()))
}
/// Access the JSON text underlying a raw value.
///
/// # Example
///
/// ```
/// #[macro_use]
/// extern crate serde_derive;
/// extern crate serde_json;
///
/// 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(())
/// }
/// ```
pub fn get(&self) -> &str {
&self.json
}
}
pub const TOKEN: &'static str = "$serde_json::private::RawValue";
impl Serialize for RawValue {
fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
where
S: Serializer,
{
let mut s = serializer.serialize_struct(TOKEN, 1)?;
s.serialize_field(TOKEN, &self.json)?;
s.end()
}
}
impl<'de: 'a, 'a> Deserialize<'de> for &'a RawValue {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: Deserializer<'de>,
{
struct ReferenceVisitor;
impl<'de> Visitor<'de> for ReferenceVisitor {
type Value = &'de RawValue;
fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
write!(formatter, "any valid JSON value")
}
fn visit_map<V>(self, mut visitor: V) -> Result<Self::Value, V::Error>
where
V: MapAccess<'de>,
{
let value = visitor.next_key::<RawKey>()?;
if value.is_none() {
return Err(de::Error::invalid_type(Unexpected::Map, &self));
}
visitor.next_value_seed(ReferenceFromString)
}
}
deserializer.deserialize_newtype_struct(TOKEN, ReferenceVisitor)
}
}
impl<'de> Deserialize<'de> for Box<RawValue> {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: Deserializer<'de>,
{
struct BoxedVisitor;
impl<'de> Visitor<'de> for BoxedVisitor {
type Value = Box<RawValue>;
fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
write!(formatter, "any valid JSON value")
}
fn visit_map<V>(self, mut visitor: V) -> Result<Self::Value, V::Error>
where
V: MapAccess<'de>,
{
let value = visitor.next_key::<RawKey>()?;
if value.is_none() {
return Err(de::Error::invalid_type(Unexpected::Map, &self));
}
visitor.next_value_seed(BoxedFromString)
}
}
deserializer.deserialize_newtype_struct(TOKEN, BoxedVisitor)
}
}
struct RawKey;
impl<'de> Deserialize<'de> for RawKey {
fn deserialize<D>(deserializer: D) -> Result<RawKey, D::Error>
where
D: Deserializer<'de>,
{
struct FieldVisitor;
impl<'de> Visitor<'de> for FieldVisitor {
type Value = ();
fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
formatter.write_str("raw value")
}
fn visit_str<E>(self, s: &str) -> Result<(), E>
where
E: de::Error,
{
if s == TOKEN {
Ok(())
} else {
Err(de::Error::custom("unexpected raw value"))
}
}
}
deserializer.deserialize_identifier(FieldVisitor)?;
Ok(RawKey)
}
}
pub struct ReferenceFromString;
impl<'de> DeserializeSeed<'de> for ReferenceFromString {
type Value = &'de RawValue;
fn deserialize<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
where
D: Deserializer<'de>,
{
deserializer.deserialize_str(self)
}
}
impl<'de> Visitor<'de> for ReferenceFromString {
type Value = &'de RawValue;
fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
formatter.write_str("raw value")
}
fn visit_borrowed_str<E>(self, s: &'de str) -> Result<Self::Value, E>
where
E: de::Error,
{
Ok(RawValue::from_borrowed(s))
}
}
pub struct BoxedFromString;
impl<'de> DeserializeSeed<'de> for BoxedFromString {
type Value = Box<RawValue>;
fn deserialize<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
where
D: Deserializer<'de>,
{
deserializer.deserialize_str(self)
}
}
impl<'de> Visitor<'de> for BoxedFromString {
type Value = Box<RawValue>;
fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
formatter.write_str("raw value")
}
fn visit_str<E>(self, s: &str) -> Result<Self::Value, E>
where
E: de::Error,
{
self.visit_string(s.to_owned())
}
fn visit_string<E>(self, s: String) -> Result<Self::Value, E>
where
E: de::Error,
{
Ok(RawValue::from_owned(s.into_boxed_str()))
}
}
struct RawKeyDeserializer;
impl<'de> Deserializer<'de> for RawKeyDeserializer {
type Error = Error;
fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Error>
where
V: de::Visitor<'de>,
{
visitor.visit_borrowed_str(TOKEN)
}
forward_to_deserialize_any! {
bool u8 u16 u32 u64 u128 i8 i16 i32 i64 i128 f32 f64 char str string seq
bytes byte_buf map struct option unit newtype_struct ignored_any
unit_struct tuple_struct tuple enum identifier
}
}
pub struct OwnedRawDeserializer {
pub raw_value: Option<String>,
}
impl<'de> MapAccess<'de> for OwnedRawDeserializer {
type Error = Error;
fn next_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>, Error>
where
K: de::DeserializeSeed<'de>,
{
if self.raw_value.is_none() {
return Ok(None);
}
seed.deserialize(RawKeyDeserializer).map(Some)
}
fn next_value_seed<V>(&mut self, seed: V) -> Result<V::Value, Error>
where
V: de::DeserializeSeed<'de>,
{
seed.deserialize(self.raw_value.take().unwrap().into_deserializer())
}
}
pub struct BorrowedRawDeserializer<'de> {
pub raw_value: Option<&'de str>,
}
impl<'de> MapAccess<'de> for BorrowedRawDeserializer<'de> {
type Error = Error;
fn next_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>, Error>
where
K: de::DeserializeSeed<'de>,
{
if self.raw_value.is_none() {
return Ok(None);
}
seed.deserialize(RawKeyDeserializer).map(Some)
}
fn next_value_seed<V>(&mut self, seed: V) -> Result<V::Value, Error>
where
V: de::DeserializeSeed<'de>,
{
seed.deserialize(BorrowedStrDeserializer::new(self.raw_value.take().unwrap()))
}
}