Changes required for reasonable upload/download speed (#265)

Increase blocksize from ~8KiB to ~64KiB and remove useless unbounded prefetching on download
* increased upload/download speed on my Win10 Zen3 box to 50/150 MB/s (with FSStore)
* made manifest files 8x smaller
* two more changes in the tests to make them pass
Closes #263

codex/blocktype.nim

@@ -22,7 +22,9 @@ import pkg/questionable/results
 import ./errors
 
 const
-  BlockSize* = 31 * 64 * 4 # block size
+  # Size of blocks for storage / network exchange,
+  # should be divisible by 31 for PoR and by 64 for Leopard ECC
+  BlockSize* = 31 * 64 * 33
 
 type
   Block* = ref object of RootObj

codex/node.nim

@@ -138,7 +138,7 @@ proc retrieve*(
         except CatchableError as exc:
           trace "Exception prefetching blocks", exc = exc.msg
       #
-      asyncSpawn prefetchBlocks()
+      # asyncSpawn prefetchBlocks()  - temporarily commented out
     #
     # Retrieve all blocks of the dataset sequentially from the local store or network
     return LPStream(StoreStream.new(node.blockStore, manifest, pad = false)).success

tests/codex/testnode.nim

@@ -128,7 +128,7 @@ suite "Test Node":
     let
       stream = BufferStream.new()
       storeFut = node.store(stream)
-      oddChunkSize = math.trunc(BlockSize/1.618).int  # Let's check that node.store can correctly rechunk these odd chunks
+      oddChunkSize = math.trunc(BlockSize/3.14).int  # Let's check that node.store can correctly rechunk these odd chunks
       oddChunker = FileChunker.new(file = file, chunkSize = oddChunkSize, pad = false)  # TODO: doesn't work with pad=tue
     var
       original: seq[byte]

tests/testIntegration.nim

@@ -80,7 +80,7 @@ ethersuite "Integration tests":
 
   test "nodes negotiate contracts on the marketplace":
     proc sell =
-      let json = %*{"size": "0x1F00", "duration": "0x200", "minPrice": "0x300"}
+      let json = %*{"size": "0xFFFFF", "duration": "0x200", "minPrice": "0x300"}
       discard client.post(baseurl2 & "/sales/availability", $json)
 
     proc available: JsonNode =