Use serde_json::from_str instead of from_reader when deserialize Json

`serde_json::from_reader` is considerably slow for some reason.

serde-rs/json#160

Author: messense

contrib/src/json.rs

@@ -1,5 +1,5 @@
 use std::ops::{Deref, DerefMut};
-use std::io::Read;
+use std::io::{self, Read};
 
 use rocket::outcome::{Outcome, IntoOutcome};
 use rocket::request::Request;
@@ -88,18 +88,23 @@ impl<T> Json<T> {
 const LIMIT: u64 = 1 << 20;
 
 impl<T: DeserializeOwned> FromData for Json<T> {
-    type Error = SerdeError;
+    type Error = io::Error;
 
-    fn from_data(request: &Request, data: Data) -> data::Outcome<Self, SerdeError> {
+    fn from_data(request: &Request, data: Data) -> data::Outcome<Self, io::Error> {
         if !request.content_type().map_or(false, |ct| ct.is_json()) {
             error_!("Content-Type is not JSON.");
             return Outcome::Forward(data);
         }
 
         let size_limit = request.limits().get("json").unwrap_or(LIMIT);
-        serde_json::from_reader(data.open().take(size_limit))
+        let mut buf = String::new();
+        if let Err(e) = data.open().take(size_limit).read_to_string(&mut buf) {
+            error_!("IO Error: {:?}", e);
+            return Outcome::Failure((Status::BadRequest, e));
+        }
+        serde_json::from_str(&buf)
             .map(|val| Json(val))
-            .map_err(|e| { error_!("Couldn't parse JSON body: {:?}", e); e })
+            .map_err(|e| { error_!("Couldn't parse JSON body: {:?}", e); e.into() })
             .into_outcome(Status::BadRequest)
     }
 }