From 13cb901a63b26064ecca571a66e5bd18dcf22f9c Mon Sep 17 00:00:00 2001
From: Emery Hemingway <ehmry@posteo.net>
Date: Fri, 8 Feb 2019 14:30:08 +0100
Subject: [PATCH] WiP! Replicator

---
 src/blobsets/replicator.nim | 121 ++++++++++++++++++++++--------------
 1 file changed, 73 insertions(+), 48 deletions(-)

diff --git a/src/blobsets/replicator.nim b/src/blobsets/replicator.nim
index f68af85..15b888d 100644
--- a/src/blobsets/replicator.nim
+++ b/src/blobsets/replicator.nim
@@ -1,54 +1,79 @@
-import std/streams, std/strutils, std/os, cbor
-import ../blobsets, ./stores
+type
+  RepBlobStream = ref RepBlobStreamObj
+  RepBlobStreamObj = object of BlobStreamObj
+    src: BlobStream
+    dst: IngestStream
+    id: BlobId
+    size: BiggestInt
+    ingestPos: BiggestInt
+
+proc repClose(s: BlobStream) =
+  var s = (RepBlobStream)s
+  close s.src
+  cancel s.dst
+
+proc finish(s: RepBlobStream) =
+  var buf = ""
+  while s.ingestPos < s.size:
+    buf.setLen(min(blobLeafSize, s.size - s.ingestPos))
+    let n = read(s.src, buf, buf.len)
+    ingest(s.dst, buf, n)
+    inc s.ingestPos, n
+
+proc repSetPos(s: BlobStream; pos: BiggestInt) =
+  var s = (RepBlobStream)s
+  if pos != ingestPos and s.ingestPos < s.size:
+    finish s
+  s.src.pos = pos
+
+proc repGetPos(s: BlobStream): BiggestInt =
+  var s = (RepBlobStream)s
+  s.src.pos
+
+proc repRead(s: BlobStream; buffer: pointer; bufLen: int): int =
+  var s = (RepBlobStream)s
+  result = read(s.src, buffer, bufLen)
+  if s.ingestPos < s.size:
+    if bufLen < blobLeafSize:
+      finish s
+    else:
+      ingest(s.dst, buffer, result)
 
 type
-  DagfsReplicator* = ref DagfsReplicatorObj
-  DagfsReplicatorObj* = object of DagfsStoreObj
-    toStore, fromStore: DagfsStore
-    cache: string
-    cacheCid: Cid
+  RepStore = ref RepStoreObj
+  RepStoreObj = object of BlobStoreObj
+    src, dst: BlobStore
 
-proc replicatedPut(s: DagfsStore; blk: string): Cid =
-  var r = DagfsReplicator(s)
-  r.toStore.put blk
+proc replicatorOpenBlobStream(store: BlobStore; id: BlobId; size: BiggestInt; kind: BlobKind) =
+  var
+    store = (RepStore)store
+  try:
+    result = openBlobStream(store.dst, id, size, kind)
+  except KeyError:
+    let
+      src = openBlobStream(store.src, id, size, kind)
+      dst = openIngestStream(store.dst, size, kind)
+      size = if 0 < size: size else: src.size
+    result = RepStore(
+      closeImpl: repClose,
+      setPosImpl: repSetPos,
+      getPosImpl: repGetPos,
+      readImpl: repRead,
+      dst: src, dst: dst, id: id, size: size
+    )
 
-proc replicatedGetBuffer(s: DagfsStore; cid: Cid; buf: pointer; len: Natural): int =
-  var r = DagfsReplicator(s)
-  if r.cacheCid == cid:
-    assert(cid.verify(r.cache), "cached block is invalid from previous get")
-    if r.cache.len > len:
-      raise newException(BufferTooSmall, "")
-    result = r.cache.len
-    copyMem(buf, r.cache[0].addr, result)
-  else:
-    try:
-      result = r.toStore.getBuffer(cid, buf, len)
-      r.cacheCid = cid
-      r.cache.setLen result
-      copyMem(r.cache[0].addr, buf, result)
-      assert(cid.verify(r.cache), "cached block is invalid after copy from To store")
-    except MissingObject:
-      result = r.fromStore.getBuffer(cid, buf, len)
-      r.cacheCid = cid
-      r.cache.setLen result
-      copyMem(r.cache[0].addr, buf, result)
-      assert(cid.verify(r.cache), "replicate cache is invalid after copy from From store")
-      discard r.toStore.put r.cache
+proc replicatorOpenIngestStream(s: BlobStore; size: BiggestInt; kind: BlobKind) =
+  openIngestStream(RepStore(store).dst)
 
-proc replicatedGet(s: DagfsStore; cid: Cid; result: var string) =
-  var r = DagfsReplicator(s)
-  try: r.toStore.get(cid, result)
-  except MissingObject:
-    r.fromStore.get(cid, result)
-    discard r.toStore.put result
+proc replicatorCloseStore(s: BlobStore) =
+  var s = (RepStore)s
+  close s.src
+  close s.dst
 
-proc newDagfsReplicator*(toStore, fromStore: DagfsStore): DagfsReplicator =
-  ## Blocks retrieved by `get` are not verified.
-  DagfsReplicator(
-    putImpl: replicatedPut,
-    getBufferImpl: replicatedGetBuffer,
-    getImpl: replicatedGet,
-    toStore: toStore,
-    fromStore: fromStore,
-    cache: "",
-    cacheCid: initCid())
+proc newReplicatorStore*(src, dst: Store): BlobStore =
+  RepStore(
+    closeImpl: replicatorCloseStore,
+    openBlobStreamImpl: replicatorOpenBlobStream,
+    openIngestStreamImpl: replicatorOpenIngestStream,
+    src: src, dst: dst,
+  )