Reimplementing bencoding with Serde. Scaffolding setup. WIP

Cargo.lock

@@ -1069,6 +1069,7 @@ dependencies = [
  "hex-literal",
  "rand",
  "reqwest",
+ "serde",
  "sha1",
  "urlencoding",
 ]

Cargo.toml

@@ -9,6 +9,7 @@ sha1 = "0.10.6"
 reqwest = { version = "0.12.5", features = ["blocking"] }
 rand = "0.8.5"
 urlencoding = "2.1.3"
+serde = "1.0.204"
 
 [dev-dependencies]
 hex-literal = "0.4.1"

src/main.rs

@@ -9,6 +9,7 @@ use reqwest::Url;
 use crate::bencode::{Bencode, ByteString};
 
 mod bencode;
+mod serde_bencode;
 
 #[derive(Debug)]
 struct FileInfo {
@@ -217,8 +218,8 @@ fn main() -> Result<()> {
     let resp = client.get(url).send()?;
     let status = resp.status();
 
-    let body = resp.text()?;
-    println!("Response: {} {}", status, body);
+    // let body = resp.text()?;
+    println!("Response: {status}");
 
     Ok(())
 }

src/serde_bencode.rs

@@ -0,0 +1,315 @@
+use std::fmt;
+use std::fmt::Display;
+use std::ops::{AddAssign, MulAssign};
+
+use serde::{de, Deserialize, ser};
+use serde::de::Visitor;
+
+pub type Result<T> = std::result::Result<T, Error>;
+
+#[derive(Debug, PartialEq)]
+pub enum Error {
+    Message(String),
+
+    Eof,
+    Syntax,
+    ExpectedInteger,
+    ExpectedListEnd,
+    ExpectedDictEnd,
+    TrailingCharacters,
+}
+
+impl ser::Error for Error {
+    fn custom<T: Display>(msg: T) -> Self {
+        Error::Message(msg.to_string())
+    }
+}
+
+impl de::Error for Error {
+    fn custom<T: Display>(msg: T) -> Self {
+        Error::Message(msg.to_string())
+    }
+}
+
+impl Display for Error {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Error::Message(msg) => formatter.write_str(msg),
+            Error::Eof => formatter.write_str("unexpected end of input"),
+            Error::Syntax => formatter.write_str("syntax error"),
+            Error::ExpectedInteger => formatter.write_str("expected integer"),
+            Error::ExpectedListEnd => formatter.write_str("expected list end char 'e'"),
+            Error::ExpectedDictEnd => formatter.write_str("expected dict end char 'e'"),
+            Error::TrailingCharacters => formatter.write_str("trailing characters")
+        }
+    }
+}
+
+impl std::error::Error for Error {}
+
+pub struct Deserializer<'de> {
+    input: &'de [u8],
+}
+
+impl<'de> Deserializer<'de> {
+    pub fn from_bytes(input: &'de [u8]) -> Self {
+        Deserializer { input }
+    }
+}
+
+pub fn from_bytes<'a, T>(b: &'a &[u8]) -> Result<T>
+where
+    T: Deserialize<'a>,
+{
+    let mut deserializer = Deserializer::from_bytes(b);
+    let t = T::deserialize(&mut deserializer)?;
+    if deserializer.input.is_empty() {
+        Ok(t)
+    } else {
+        Err(Error::TrailingCharacters)
+    }
+}
+
+impl<'de> Deserializer<'de> {
+    fn peek_byte(&mut self) -> Result<u8> {
+        if let Some(&result) = self.input.get(0) {
+            Ok(result)
+        } else {
+            Err(Error::Eof)
+        }
+    }
+
+    fn parse_int<T>(&mut self) -> Result<T>
+    where
+        //T: AddAssign<T> + MulAssign<T> + From<i8>,
+        T:  From<i8>,
+    {
+        Ok(42.into())
+    }
+}
+
+impl <'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
+    type Error = Error;
+
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>
+    {
+        todo!()
+    }
+
+    fn deserialize_bool<V>(self, _: V) -> std::result::Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_i8<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>
+    {
+        visitor.visit_i8(self.parse_int()?)
+    }
+
+    fn deserialize_i16<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>
+    {
+        visitor.visit_i16(self.parse_int()?)
+    }
+
+    fn deserialize_i32<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>
+    {
+        visitor.visit_i32(self.parse_int()?)
+    }
+
+    fn deserialize_i64<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>
+    {
+        visitor.visit_i64(self.parse_int()?)
+    }
+
+    fn deserialize_i128<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>
+    {
+        visitor.visit_i128(self.parse_int()?)
+    }
+
+    fn deserialize_u8<V>(self, _: V) -> std::result::Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_u16<V>(self, _: V) -> std::result::Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_u32<V>(self, _: V) -> std::result::Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_u64<V>(self, _: V) -> std::result::Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_f32<V>(self, _: V) -> std::result::Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_f64<V>(self, _: V) -> std::result::Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_char<V>(self, _: V) -> std::result::Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_str<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>
+    {
+        todo!()
+    }
+
+    fn deserialize_string<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>
+    {
+        todo!()
+    }
+
+    fn deserialize_bytes<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>
+    {
+        todo!()
+    }
+
+    fn deserialize_byte_buf<V>(self, visitor: V) -> std::result::Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>
+    {
+        todo!()
+    }
+
+    fn deserialize_option<V>(self, visitor: V) -> std::result::Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_unit<V>(self, _: V) -> std::result::Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_unit_struct<V>(self, _: &'static str, _: V) -> std::result::Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_newtype_struct<V>(self, name: &'static str, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>
+    {
+        todo!()
+    }
+
+    fn deserialize_seq<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>
+    {
+        todo!()
+    }
+
+    fn deserialize_tuple<V>(self, _: usize, _: V) -> std::result::Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_tuple_struct<V>(self, _: &'static str, _: usize, _: V) -> std::result::Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_map<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>
+    {
+        todo!()
+    }
+
+    fn deserialize_struct<V>(self, name: &'static str, fields: &'static [&'static str], visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>
+    {
+        todo!()
+    }
+
+    fn deserialize_enum<V>(self, _: &'static str, _: &'static [&'static str], _: V) -> std::result::Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>
+    {
+        unimplemented!()
+    }
+
+    fn deserialize_identifier<V>(self, visitor: V) -> std::result::Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>
+    {
+        todo!()
+    }
+
+    fn deserialize_ignored_any<V>(self, visitor: V) -> std::result::Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>
+    {
+        todo!()
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::serde_bencode::from_bytes;
+
+    #[test]
+    fn test_int() {
+        assert_eq!(from_bytes(&"i42e".as_bytes()), Ok(42));
+        // 2**16 + 1 = 65537
+        assert_eq!(from_bytes(&"i65537e".as_bytes()), Ok(65537));
+    }
+}