[feat] Add support for content ranges/seeking

codex/node.nim

@@ -14,6 +14,7 @@ import std/sequtils
 import std/strformat
 import std/sugar
 import times
+import std/streams
 
 import pkg/taskpools
 import pkg/questionable
@@ -37,6 +38,7 @@ import ./merkletree
 import ./stores
 import ./blockexchange
 import ./streams
+import ./streams/rangestream
 import ./erasure
 import ./discovery
 import ./contracts
@@ -325,10 +327,78 @@ proc retrieve*(
     if err of AsyncTimeoutError:
       return failure(err)
 
+    # Not a manifest, must be a single block
     return await self.streamSingleBlock(cid)
 
   await self.streamEntireDataset(manifest, cid)
 
+proc retrieveLocalRange*(
+    self: CodexNodeRef, cid: Cid, rangeStart: int, rangeEnd: int
+): Future[?!LPStream] {.async.} =
+  ## Retrieve a specific byte range efficiently using only the local block store.
+  without manifest =? (await self.fetchManifest(cid)), err:
+    # Manifest fetch might still go to network if not local, but block reads won't.
+    return failure(err)
+
+  let 
+    totalSize = (if manifest.protected: manifest.originalDatasetSize else: manifest.datasetSize).int
+    clampedEnd = min(rangeEnd, totalSize - 1) # Ensure end is within bounds
+    contentLength = if clampedEnd >= rangeStart: clampedEnd - rangeStart + 1 else: 0
+
+  if contentLength <= 0:
+    # Requested range is impossible or zero length
+    warn "Invalid or zero-length local range requested", cid, rangeStart, rangeEnd, totalSize
+    let emptyStream = BufferStream.new() # Use BufferStream
+    await emptyStream.pushEof()         # Mark as immediately finished
+    # Return with correct type signature but preserve instance identity
+    return success(LPStream(emptyStream))
+
+  let stream = RangeStream.new(
+    self.blockStore(), # Use local store
+    manifest, 
+    rangeStart, 
+    contentLength,
+    pad = false # Assuming padding is not needed for local retrieval
+  )
+  # Initialize the stream to ensure its objName is set to enable tracing
+  stream.initStream()
+  trace "Local range stream created", cid, rangeStart, rangeEnd, contentLength
+  # Return with correct type signature but preserve instance identity
+  return success(LPStream(stream))
+
+proc retrieveNetworkRange*(
+    self: CodexNodeRef, cid: Cid, rangeStart: int, rangeEnd: int
+): Future[?!LPStream] {.async.} =
+  ## Retrieve a specific byte range efficiently using the network store.
+  without manifest =? (await self.fetchManifest(cid)), err:
+    return failure(err)
+
+  let 
+    totalSize = (if manifest.protected: manifest.originalDatasetSize else: manifest.datasetSize).int
+    clampedEnd = min(rangeEnd, totalSize - 1) # Ensure end is within bounds
+    contentLength = if clampedEnd >= rangeStart: clampedEnd - rangeStart + 1 else: 0
+
+  if contentLength <= 0:
+    # Requested range is impossible or zero length
+    warn "Invalid or zero-length network range requested", cid, rangeStart, rangeEnd, totalSize
+    let emptyStream = BufferStream.new() # Use BufferStream
+    await emptyStream.pushEof()         # Mark as immediately finished
+    # Return with correct type signature but preserve instance identity
+    return success(LPStream(emptyStream)) 
+
+  let stream = RangeStream.new(
+    self.networkStore, # Use network store
+    manifest, 
+    rangeStart, 
+    contentLength,
+    pad = false # Assuming padding is not needed here either
+  )
+  # Initialize the stream to ensure its objName is set to enable tracing 
+  stream.initStream()
+  trace "Network range stream created", cid, rangeStart, rangeEnd, contentLength
+  # Return with correct type signature but preserve instance identity
+  return success(LPStream(stream))
+
 proc deleteSingleBlock(self: CodexNodeRef, cid: Cid): Future[?!void] {.async.} =
   if err =? (await self.networkStore.delBlock(cid)).errorOption:
     error "Error deleting block", cid, err = err.msg