[serde_bencode] Implemented sequences

src/serde_bencode.rs

@@ -2,7 +2,7 @@ use std::fmt;
 use std::fmt::Display;
 use std::str::Utf8Error;
 use serde::{de, Deserialize, ser};
-use serde::de::Visitor;
+use serde::de::{DeserializeSeed, SeqAccess, Visitor};
 
 pub type Result<T> = std::result::Result<T, Error>;
 
@@ -10,12 +10,18 @@ pub type Result<T> = std::result::Result<T, Error>;
 pub enum Error {
     Message(String),
 
+    WontImplement,
     Eof,
     Syntax,
     InvalidUtf8,
+    ExpectedBytes,
+    ExpectedBytesSep,
+    ExpectedNumbers,
     ExpectedInteger,
     ExpectedIntegerEnd,
+    ExpectedList,
     ExpectedListEnd,
+    ExpectedDict,
     ExpectedDictEnd,
     TrailingCharacters,
 }
@@ -42,12 +48,18 @@ impl Display for Error {
     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
         match self {
             Error::Message(msg) => formatter.write_str(msg),
+            Error::WontImplement => formatter.write_str("there is no reasonable way to deserialize to this type"),
             Error::Eof => formatter.write_str("unexpected end of input"),
             Error::Syntax => formatter.write_str("syntax error"),
             Error::InvalidUtf8 => formatter.write_str("could not decoded as UTF-8"),
-            Error::ExpectedInteger => formatter.write_str("expected integer"),
+            Error::ExpectedBytes => formatter.write_str("expected byte string start char: any number"),
+            Error::ExpectedBytesSep => formatter.write_str("expected byte separator char: ':'"),
+            Error::ExpectedInteger => formatter.write_str("expected integer start char 'i'"),
+            Error::ExpectedNumbers => formatter.write_str("expected numbers"),
             Error::ExpectedIntegerEnd => formatter.write_str("expected integer end char 'e'"),
+            Error::ExpectedList => formatter.write_str("expected list start char 'l'"),
             Error::ExpectedListEnd => formatter.write_str("expected list end char 'e'"),
+            Error::ExpectedDict => formatter.write_str("expected dict start char 'd'"),
             Error::ExpectedDictEnd => formatter.write_str("expected dict end char 'e'"),
             Error::TrailingCharacters => formatter.write_str("trailing characters")
         }
@@ -99,21 +111,21 @@ impl<'de> Deserializer<'de> {
         T:  std::str::FromStr,
     {
         if self.next_byte()? != 'i' as u8 {
-            return Err(Error::Syntax)
+            return Err(Error::ExpectedInteger)
         }
         let end_pos = self.input.iter().position(|&x| x == 'e' as u8)
             .ok_or_else(|| Error::ExpectedIntegerEnd)?;
         let int_str = std::str::from_utf8(&self.input[..end_pos])?;
-        let int = int_str.parse::<T>().map_err(|_| Error::ExpectedInteger)?;
+        let int = int_str.parse::<T>().map_err(|_| Error::ExpectedNumbers)?;
         self.input = &self.input[end_pos + 1..];
         Ok(int)
     }
 
     fn parse_byte_string(&mut self) -> Result<&'de [u8]> {
         let delim_pos = self.input.iter().position(|&x| x == ':' as u8)
-            .ok_or_else(|| Error::Syntax)?;
+            .ok_or_else(|| Error::ExpectedBytesSep)?;
         let int_str = std::str::from_utf8(&self.input[..delim_pos])?;
-        let str_len = int_str.parse().map_err(|_| Error::ExpectedInteger)?;
+        let str_len = int_str.parse().map_err(|_| Error::ExpectedNumbers)?;
         self.input = &self.input[delim_pos + 1..];
         let res = &self.input[..str_len];
         self.input = &self.input[str_len..];
@@ -124,18 +136,19 @@ impl<'de> Deserializer<'de> {
 impl <'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
     type Error = Error;
 
-    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value>
+    fn deserialize_any<V>(self, _: V) -> Result<V::Value>
     where
         V: Visitor<'de>
     {
-        todo!()
+        println!("i don't get this API!");
+        Err(Error::WontImplement)
     }
 
     fn deserialize_bool<V>(self, _: V) -> std::result::Result<V::Value, Self::Error>
     where
         V: Visitor<'de>
     {
-        unimplemented!()
+        Err(Error::WontImplement)
     }
 
     fn deserialize_i8<V>(self, visitor: V) -> Result<V::Value>
@@ -177,42 +190,42 @@ impl <'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
     where
         V: Visitor<'de>
     {
-        unimplemented!()
+        Err(Error::WontImplement)
     }
 
     fn deserialize_u16<V>(self, _: V) -> std::result::Result<V::Value, Self::Error>
     where
         V: Visitor<'de>
     {
-        unimplemented!()
+        Err(Error::WontImplement)
     }
 
     fn deserialize_u32<V>(self, _: V) -> std::result::Result<V::Value, Self::Error>
     where
         V: Visitor<'de>
     {
-        unimplemented!()
+        Err(Error::WontImplement)
     }
 
     fn deserialize_u64<V>(self, _: V) -> std::result::Result<V::Value, Self::Error>
     where
         V: Visitor<'de>
     {
-        unimplemented!()
+        Err(Error::WontImplement)
     }
 
     fn deserialize_f32<V>(self, _: V) -> std::result::Result<V::Value, Self::Error>
     where
         V: Visitor<'de>
     {
-        unimplemented!()
+        Err(Error::WontImplement)
     }
 
     fn deserialize_f64<V>(self, _: V) -> std::result::Result<V::Value, Self::Error>
     where
         V: Visitor<'de>
     {
-        unimplemented!()
+        Err(Error::WontImplement)
     }
 
     fn deserialize_char<V>(self, visitor: V) -> std::result::Result<V::Value, Self::Error>
@@ -268,49 +281,58 @@ impl <'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
     where
         V: Visitor<'de>
     {
-        unimplemented!()
+        Err(Error::WontImplement)
     }
 
     fn deserialize_unit<V>(self, _: V) -> std::result::Result<V::Value, Self::Error>
     where
         V: Visitor<'de>
     {
-        unimplemented!()
+        Err(Error::WontImplement)
     }
 
     fn deserialize_unit_struct<V>(self, _: &'static str, _: V) -> std::result::Result<V::Value, Self::Error>
     where
         V: Visitor<'de>
     {
-        unimplemented!()
+        Err(Error::WontImplement)
     }
 
-    fn deserialize_newtype_struct<V>(self, name: &'static str, visitor: V) -> Result<V::Value>
+    fn deserialize_newtype_struct<V>(self, _name: &'static str, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>
     {
-        todo!()
+        visitor.visit_newtype_struct(self)
     }
 
     fn deserialize_seq<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>
     {
-        todo!()
+        if self.next_byte()? as char != 'l'{
+            Err(Error::ExpectedList)
+        } else {
+            let value = visitor.visit_seq(Access::new(self))?;
+            if self.next_byte()? as char != 'e' {
+                Err(Error::ExpectedListEnd)
+            } else {
+                Ok(value)
+            }
+        }
     }
 
     fn deserialize_tuple<V>(self, _: usize, _: V) -> std::result::Result<V::Value, Self::Error>
     where
         V: Visitor<'de>
     {
-        unimplemented!()
+        Err(Error::WontImplement)
     }
 
     fn deserialize_tuple_struct<V>(self, _: &'static str, _: usize, _: V) -> std::result::Result<V::Value, Self::Error>
     where
         V: Visitor<'de>
     {
-        unimplemented!()
+        Err(Error::WontImplement)
     }
 
     fn deserialize_map<V>(self, visitor: V) -> Result<V::Value>
@@ -331,7 +353,7 @@ impl <'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
     where
         V: Visitor<'de>
     {
-        unimplemented!()
+        Err(Error::WontImplement)
     }
 
     fn deserialize_identifier<V>(self, visitor: V) -> std::result::Result<V::Value, Self::Error>
@@ -349,6 +371,35 @@ impl <'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
     }
 }
 
+struct Access<'a, 'de: 'a> {
+    de: &'a mut Deserializer<'de>,
+}
+
+impl <'a, 'de> Access<'a, 'de> {
+    fn new(de: &'a mut Deserializer<'de>) -> Self {
+        Access {
+            de,
+        }
+    }
+}
+
+impl<'a, 'de> SeqAccess<'de> for Access<'a, 'de> {
+    type Error = Error;
+
+    fn next_element_seed<T>(&mut self, seed: T) -> std::result::Result<Option<T::Value>, Self::Error>
+    where
+        T: DeserializeSeed<'de>
+    {
+        match self.de.peek_byte()? as char {
+            'd' | 'i' | 'l' | '0'..='9' => {
+                seed.deserialize(&mut *self.de).map(Some)
+            },
+            'e' => Ok(None),
+            _ => Err(Error::Syntax)
+        }
+    }
+}
+
 #[cfg(test)]
 mod test {
     use crate::serde_bencode::{Error, from_bytes};
@@ -371,4 +422,10 @@ mod test {
         assert_eq!(from_bytes(&"1:a".as_bytes()), Ok('a'));
         assert_eq!(from_bytes(&"4:💩".as_bytes()), Ok('💩'));
     }
+
+    #[test]
+    fn test_list() {
+        assert_eq!(from_bytes(&"li42ei13ee".as_bytes()), Ok(vec![42, 13]));
+        assert_eq!(from_bytes(&"l3:foo4:barie".as_bytes()), Ok(vec!["foo", "bari"]));
+    }
 }