feat: add a shardFanoutBits option to the importer

packages/ipfs-unixfs-exporter/src/resolvers/unixfs-v1/content/hamt-sharded-directory.ts

@@ -1,4 +1,6 @@
 import { decode, type PBNode } from '@ipld/dag-pb'
+import errCode from 'err-code'
+import { UnixFS } from 'ipfs-unixfs'
 import map from 'it-map'
 import parallel from 'it-parallel'
 import { pipe } from 'it-pipe'
@@ -20,11 +22,28 @@ const hamtShardedDirectoryContent: UnixfsV1Resolver = (cid, node, unixfs, path,
 async function * listDirectory (node: PBNode, path: string, resolve: Resolve, depth: number, blockstore: ReadableStorage, options: ExporterOptions): UnixfsV1DirectoryContent {
   const links = node.Links
 
+  if (node.Data == null) {
+    throw errCode(new Error('no data in PBNode'), 'ERR_NOT_UNIXFS')
+  }
+
+  let dir: UnixFS
+  try {
+    dir = UnixFS.unmarshal(node.Data)
+  } catch (err: any) {
+    throw errCode(err, 'ERR_NOT_UNIXFS')
+  }
+
+  if (!dir.fanout) {
+    throw errCode(new Error('missing fanout'), 'ERR_NOT_UNIXFS')
+  }
+
+  const padLength = (dir.fanout - 1n).toString(16).length
+
   const results = pipe(
     links,
     source => map(source, link => {
       return async () => {
-        const name = link.Name != null ? link.Name.substring(2) : null
+        const name = link.Name != null ? link.Name.substring(padLength) : null
 
         if (name != null && name !== '') {
           const result = await resolve(link.Hash, name, `${path}/${name}`, [], depth + 1, blockstore, options)

packages/ipfs-unixfs/src/index.ts

@@ -52,7 +52,8 @@ class UnixFS {
             secs: message.mtime.Seconds ?? 0n,
             nsecs: message.mtime.FractionalNanoseconds
           }
-        : undefined
+        : undefined,
+      fanout: message.fanout
     })
 
     // make sure we honour the original mode