Make the /resolve_magnet HTTP endpoint return an actual torrent file, not info

crates/bencode/src/lib.rs

@@ -1,4 +1,5 @@
 mod bencode_value;
+pub mod raw_value;
 mod serde_bencode_de;
 mod serde_bencode_ser;
 

crates/bencode/src/raw_value.rs

@@ -0,0 +1,28 @@
+use serde::Serialize;
+
+pub struct RawValue<T>(pub T);
+
+pub(crate) const TAG: &str = "::librqbit_bencode::RawValue";
+
+impl<T> Serialize for RawValue<T>
+where
+    T: AsRef<[u8]>,
+{
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        struct Wrapper<'a>(&'a [u8]);
+
+        impl<'a> Serialize for Wrapper<'a> {
+            fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+            where
+                S: serde::Serializer,
+            {
+                serializer.serialize_bytes(self.0)
+            }
+        }
+
+        serializer.serialize_newtype_struct(TAG, &Wrapper(self.0.as_ref()))
+    }
+}

crates/bencode/src/serde_bencode_de.rs

@@ -10,6 +10,7 @@ pub struct BencodeDeserializer<'de> {
     // This is a f**ing hack
     pub is_torrent_info: bool,
     pub torrent_info_digest: Option<[u8; 20]>,
+    pub torrent_info_bytes: Option<&'de [u8]>,
 }
 
 impl<'de> BencodeDeserializer<'de> {
@@ -20,6 +21,7 @@ impl<'de> BencodeDeserializer<'de> {
             parsing_key: false,
             is_torrent_info: false,
             torrent_info_digest: None,
+            torrent_info_bytes: None,
         }
     }
     pub fn into_remaining(self) -> &'de [u8] {
@@ -542,9 +544,11 @@ impl<'a, 'de> serde::de::MapAccess<'de> for MapAccess<'a, 'de> {
         if self.de.is_torrent_info && self.de.field_context.as_slice() == [ByteBuf(b"info")] {
             let len = self.de.buf.as_ptr() as usize - buf_before.as_ptr() as usize;
             let mut hash = Sha1::new();
-            hash.update(&buf_before[..len]);
+            let torrent_info_bytes = &buf_before[..len];
+            hash.update(torrent_info_bytes);
             let digest = hash.finish();
-            self.de.torrent_info_digest = Some(digest)
+            self.de.torrent_info_digest = Some(digest);
+            self.de.torrent_info_bytes = Some(torrent_info_bytes);
         }
         self.de.field_context.pop();
         Ok(value)

crates/bencode/src/serde_bencode_ser.rs

@@ -328,12 +328,18 @@ impl<'ser, W: std::io::Write> Serializer for &'ser mut BencodeSerializer<W> {
 
     fn serialize_newtype_struct<T>(
         self,
-        _name: &'static str,
-        _value: &T,
+        name: &'static str,
+        value: &T,
     ) -> Result<Self::Ok, Self::Error>
     where
         T: ?Sized + serde::Serialize,
     {
+        if name == crate::raw_value::TAG {
+            self.hack_no_bytestring_prefix = true;
+            value.serialize(&mut *self)?;
+            self.hack_no_bytestring_prefix = false;
+            return Ok(());
+        }
         Err(SerError::custom_with_ser(
             "bencode doesn't support newtype structs",
             self,

crates/librqbit/src/session.rs

@@ -502,13 +502,23 @@ async fn create_tcp_listener(
     bail!("no free TCP ports in range {port_range:?}");
 }
 
-fn torrent_file_from_info_and_bytes(
-    info: &TorrentMetaV1Info<ByteBufOwned>,
-    info_hash: &Id20,
-    info_bytes: &[u8],
-    trackers: &[String],
-) -> Bytes {
-    todo!()
+fn torrent_file_from_info_bytes(info_bytes: &[u8], trackers: &[String]) -> anyhow::Result<Bytes> {
+    #[derive(Serialize)]
+    struct Tmp<'a> {
+        announce: &'a str,
+        #[serde(rename = "announce-list")]
+        announce_list: &'a [&'a [String]],
+        info: bencode::raw_value::RawValue<&'a [u8]>,
+    }
+
+    let mut w = Vec::new();
+    let v = Tmp {
+        info: bencode::raw_value::RawValue(info_bytes),
+        announce: trackers.first().map(|s| s.as_str()).unwrap_or(""),
+        announce_list: &[trackers],
+    };
+    bencode_serialize_to_writer(&v, &mut w)?;
+    Ok(w.into())
 }
 
 pub(crate) struct CheckedIncomingConnection {
@@ -1003,12 +1013,10 @@ impl Session {
                             let trackers = magnet.trackers.into_iter().unique().collect_vec();
                             InternalAddResult {
                                 info_hash,
-                                torrent_bytes: torrent_file_from_info_and_bytes(
-                                    &info,
-                                    &info_hash,
+                                torrent_bytes: torrent_file_from_info_bytes(
                                     &info_bytes,
                                     &trackers,
-                                ),
+                                )?,
                                 info,
                                 trackers,
                                 peer_rx: Some(rx),
@@ -1427,3 +1435,46 @@ impl tracker_comms::TorrentStatsProvider for PeerRxTorrentInfo {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use std::io::Write;
+
+    use buffers::ByteBuf;
+    use itertools::Itertools;
+    use librqbit_core::torrent_metainfo::{torrent_from_bytes_ext, TorrentMetaV1};
+
+    use super::torrent_file_from_info_bytes;
+
+    #[test]
+    fn test_torrent_file_from_info_and_bytes() {
+        fn get_trackers(info: &TorrentMetaV1<ByteBuf>) -> Vec<String> {
+            info.iter_announce()
+                .filter_map(|t| std::str::from_utf8(t.as_ref()).ok().map(|t| t.to_owned()))
+                .collect_vec()
+        }
+
+        let orig_full_torrent =
+            include_bytes!("../resources/ubuntu-21.04-desktop-amd64.iso.torrent");
+        let parsed = torrent_from_bytes_ext::<ByteBuf>(&orig_full_torrent[..]).unwrap();
+        let parsed_trackers = get_trackers(&parsed.meta);
+
+        let generated_torrent =
+            torrent_file_from_info_bytes(parsed.info_bytes.as_ref(), &parsed_trackers).unwrap();
+        {
+            let mut f = std::fs::OpenOptions::new()
+                .write(true)
+                .create(true)
+                .truncate(true)
+                .open("/tmp/generated")
+                .unwrap();
+            f.write_all(&generated_torrent).unwrap();
+        }
+        let generated_parsed =
+            torrent_from_bytes_ext::<ByteBuf>(generated_torrent.as_ref()).unwrap();
+        assert_eq!(parsed.meta.info_hash, generated_parsed.meta.info_hash);
+        assert_eq!(parsed.meta.info, generated_parsed.meta.info);
+        assert_eq!(parsed.info_bytes, generated_parsed.info_bytes);
+        assert_eq!(parsed_trackers, get_trackers(&generated_parsed.meta));
+    }
+}

crates/librqbit_core/src/torrent_metainfo.rs

@@ -12,18 +12,37 @@ use crate::{hash_id::Id20, lengths::Lengths};
 pub type TorrentMetaV1Borrowed<'a> = TorrentMetaV1<ByteBuf<'a>>;
 pub type TorrentMetaV1Owned = TorrentMetaV1<ByteBufOwned>;
 
-/// Parse torrent metainfo from bytes.
-pub fn torrent_from_bytes<'de, BufType: Deserialize<'de>>(
+pub struct ParsedTorrent<BufType> {
+    /// The parsed torrent.
+    pub meta: TorrentMetaV1<BufType>,
+
+    /// The raw bytes of the torrent's "info" dict.
+    pub info_bytes: BufType,
+}
+
+/// Parse torrent metainfo from bytes (includes additional fields).
+pub fn torrent_from_bytes_ext<'de, BufType: Deserialize<'de> + From<&'de [u8]>>(
     buf: &'de [u8],
-) -> anyhow::Result<TorrentMetaV1<BufType>> {
+) -> anyhow::Result<ParsedTorrent<BufType>> {
     let mut de = BencodeDeserializer::new_from_buf(buf);
     de.is_torrent_info = true;
     let mut t = TorrentMetaV1::deserialize(&mut de)?;
-    t.info_hash = Id20::new(
-        de.torrent_info_digest
-            .ok_or_else(|| anyhow::anyhow!("programming error"))?,
-    );
-    Ok(t)
+    let (digest, info_bytes) = match (de.torrent_info_digest, de.torrent_info_bytes) {
+        (Some(digest), Some(info_bytes)) => (digest, info_bytes),
+        _ => anyhow::bail!("programming error"),
+    };
+    t.info_hash = Id20::new(digest);
+    Ok(ParsedTorrent {
+        meta: t,
+        info_bytes: BufType::from(info_bytes),
+    })
+}
+
+/// Parse torrent metainfo from bytes.
+pub fn torrent_from_bytes<'de, BufType: Deserialize<'de> + From<&'de [u8]>>(
+    buf: &'de [u8],
+) -> anyhow::Result<TorrentMetaV1<BufType>> {
+    torrent_from_bytes_ext(buf).map(|r| r.meta)
 }
 
 /// A parsed .torrent file.