nim-codex/codex/streams/storestream.nim

109 lines
3.2 KiB
Nim

## Nim-Dagger
## Copyright (c) 2022 Status Research & Development GmbH
## Licensed under either of
## * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
## * MIT license ([LICENSE-MIT](LICENSE-MIT))
## at your option.
## This file may not be copied, modified, or distributed except according to
## those terms.
import std/options
import pkg/upraises
push: {.upraises: [].}
import pkg/libp2p
import pkg/chronos
import pkg/chronicles
import pkg/stew/ptrops
import ../stores
import ../manifest
import ../blocktype
import ./seekablestream
export stores, blocktype, manifest, chronos
logScope:
topics = "dagger storestream"
type
# Make SeekableStream from a sequence of blocks stored in Manifest
# (only original file data - see StoreStream.size)
StoreStream* = ref object of SeekableStream
store*: BlockStore # Store where to lookup block contents
manifest*: Manifest # List of block CIDs
pad*: bool # Pad last block to manifest.blockSize?
proc new*(
T: type StoreStream,
store: BlockStore,
manifest: Manifest,
pad = true): T =
result = T(
store: store,
manifest: manifest,
pad: pad,
offset: 0)
result.initStream()
method `size`*(self: StoreStream): int =
bytes(self.manifest, self.pad)
proc `size=`*(self: StoreStream, size: int)
{.error: "Setting the size is forbidden".} =
discard
method atEof*(self: StoreStream): bool =
self.offset >= self.size
method readOnce*(
self: StoreStream,
pbytes: pointer,
nbytes: int): Future[int] {.async.} =
## Read `nbytes` from current position in the StoreStream into output buffer pointed by `pbytes`.
## Return how many bytes were actually read before EOF was encountered.
## Raise exception if we are already at EOF.
trace "Reading from manifest", cid = self.manifest.cid.get(), blocks = self.manifest.len
if self.atEof:
raise newLPStreamEOFError()
# The loop iterates over blocks in the StoreStream,
# reading them and copying their data into outbuf
var read = 0 # Bytes read so far, and thus write offset in the outbuf
while read < nbytes and not self.atEof:
# Compute from the current stream position `self.offset` the block num/offset to read
# Compute how many bytes to read from this block
let
blockNum = self.offset div self.manifest.blockSize
blockOffset = self.offset mod self.manifest.blockSize
readBytes = min([self.size - self.offset, nbytes - read, self.manifest.blockSize - blockOffset])
# Read contents of block `blockNum`
without blk =? await self.store.getBlock(self.manifest[blockNum]), error:
raise newLPStreamReadError(error)
trace "Reading bytes from store stream", blockNum, cid = blk.cid, bytes = readBytes, blockOffset
# Copy `readBytes` bytes starting at `blockOffset` from the block into the outbuf
if blk.isEmpty:
zeroMem(pbytes.offset(read), readBytes)
else:
copyMem(pbytes.offset(read), blk.data[blockOffset].addr, readBytes)
# Update current positions in the stream and outbuf
self.offset += readBytes
read += readBytes
return read
method closeImpl*(self: StoreStream) {.async.} =
trace "Closing StoreStream"
self.offset = self.size # set Eof
await procCall LPStream(self).closeImpl()