add: dagpb getters to ipfs-unixfs

unixfs/src/dagpb.rs

@@ -0,0 +1,37 @@
+///! dag-pb support operations. Placing this module inside unixfs module is a bit unfortunate but
+///! follows from the inseparability of dag-pb and UnixFS.
+
+use std::convert::TryFrom;
+use std::borrow::Cow;
+use cid::Cid;
+use crate::pb::PBNode;
+use crate::InvalidCidInLink;
+
+/// Extracts the PBNode::Data field from the block as it appears on the block.
+pub fn node_data(block: &[u8]) -> Result<Option<&[u8]>, quick_protobuf::Error> {
+    let doc = PBNode::try_from(block)?;
+    Ok(match doc.Data {
+        Some(Cow::Borrowed(slice)) => Some(slice),
+        Some(Cow::Owned(_)) => unreachable!("never converted to owned"),
+        None => None,
+    })
+}
+
+/// Extracts the PBNode::Links as Cids usable for the ipfs `refs` operation.
+pub fn nameless_links(block: &[u8]) -> Result<Result<Vec<Cid>, InvalidCidInLink>, quick_protobuf::Error> {
+    let doc = PBNode::try_from(block)?;
+
+    Ok(doc.Links.into_iter()
+        .enumerate()
+        .map(|(nth, link)| {
+            let hash = link.Hash.as_deref().unwrap_or_default();
+
+            match Cid::try_from(hash) {
+                Ok(cid) => Ok(cid),
+                Err(e) => Err(InvalidCidInLink::from((nth, link, e))),
+            }
+        })
+        .collect::<Result<Vec<_>, _>>())
+}
+
+

unixfs/src/lib.rs

@@ -15,6 +15,9 @@ pub use dir::{resolve, LookupError, MaybeResolved, ResolveError};
 mod pb;
 use crate::pb::UnixFsType;
 
+/// Support operations for the dag-pb, the outer shell of UnixFS.
+pub mod dagpb;
+
 /// A link could not be transformed into a Cid.
 #[derive(Debug)]
 pub struct InvalidCidInLink {