storage: Move shared functionality to base (#39419)

Part of #39418. See that PR for a full description.

Moves:
- `read_json_from_file`
- `write_json_to_file`
- `IpcSendResult`
- `IpcSend`

Renames:
- `CoreResourceThreadPool` to `ThreadPool` (shorter and more
descriptive, as we use it for more than the core resource thread now)

Signed-off-by: Ashwin Naren <arihant2math@gmail.com>

components/shared/base/lib.rs

@@ -14,12 +14,62 @@ pub mod generic_channel;
 pub mod id;
 pub mod print_tree;
 pub mod text;
+pub mod threadpool;
 mod unicode_block;
 
+use std::fs::File;
+use std::io::{BufWriter, Read};
+use std::path::Path;
+
+use ipc_channel::ipc::{IpcError, IpcSender};
+use log::{trace, warn};
 use malloc_size_of_derive::MallocSizeOf;
 use serde::{Deserialize, Serialize};
 use webrender_api::Epoch as WebRenderEpoch;
 
+pub fn read_json_from_file<T>(data: &mut T, config_dir: &Path, filename: &str)
+where
+    T: for<'de> Deserialize<'de>,
+{
+    let path = config_dir.join(filename);
+    let display = path.display();
+
+    let mut file = match File::open(&path) {
+        Err(why) => {
+            warn!("couldn't open {}: {}", display, why);
+            return;
+        },
+        Ok(file) => file,
+    };
+
+    let mut string_buffer: String = String::new();
+    match file.read_to_string(&mut string_buffer) {
+        Err(why) => panic!("couldn't read from {}: {}", display, why),
+        Ok(_) => trace!("successfully read from {}", display),
+    }
+
+    match serde_json::from_str(&string_buffer) {
+        Ok(decoded_buffer) => *data = decoded_buffer,
+        Err(why) => warn!("Could not decode buffer{}", why),
+    }
+}
+
+pub fn write_json_to_file<T>(data: &T, config_dir: &Path, filename: &str)
+where
+    T: Serialize,
+{
+    let path = config_dir.join(filename);
+    let display = path.display();
+
+    let mut file = match File::create(&path) {
+        Err(why) => panic!("couldn't create {}: {}", display, why),
+        Ok(file) => file,
+    };
+    let mut writer = BufWriter::new(&mut file);
+    serde_json::to_writer_pretty(&mut writer, data).expect("Could not serialize to file");
+    trace!("successfully wrote to {display}");
+}
+
 /// A struct for denoting the age of messages; prevents race conditions.
 #[derive(
     Clone, Copy, Debug, Deserialize, Eq, Hash, Ord, PartialEq, PartialOrd, Serialize, MallocSizeOf,
@@ -50,3 +100,18 @@ impl WebRenderEpochToU16 for WebRenderEpoch {
         (self.0 % u16::MAX as u32) as u16
     }
 }
+
+pub type IpcSendResult = Result<(), IpcError>;
+
+/// Abstraction of the ability to send a particular type of message,
+/// used by net_traits::ResourceThreads to ease the use its IpcSender sub-fields
+/// XXX: If this trait will be used more in future, some auto derive might be appealing
+pub trait IpcSend<T>
+where
+    T: serde::Serialize + for<'de> serde::Deserialize<'de>,
+{
+    /// send message T
+    fn send(&self, _: T) -> IpcSendResult;
+    /// get underlying sender
+    fn sender(&self) -> IpcSender<T>;
+}