nim-codex/codex/chunker.nim

135 lines
3.2 KiB
Nim

## Nim-Codex
## Copyright (c) 2021 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.
# TODO: This is super inneficient and needs a rewrite, but it'll do for now
import pkg/upraises
push: {.upraises: [].}
import pkg/chronicles
import pkg/questionable
import pkg/questionable/results
import pkg/chronos
import pkg/libp2p except shuffle
import ./blocktype
export blocktype
const
DefaultChunkSize* = BlockSize
type
# default reader type
ChunkBuffer* = ptr UncheckedArray[byte]
Reader* = proc(data: ChunkBuffer, len: int): Future[int] {.gcsafe, raises: [Defect].}
# Reader that splits input data into fixed-size chunks
Chunker* = ref object
reader*: Reader # Procedure called to actually read the data
offset*: int # Bytes read so far (position in the stream)
chunkSize*: Natural # Size of each chunk
pad*: bool # Pad last chunk to chunkSize?
FileChunker* = Chunker
LPStreamChunker* = Chunker
proc getBytes*(c: Chunker): Future[seq[byte]] {.async.} =
## returns a chunk of bytes from
## the instantiated chunker
##
var buff = newSeq[byte](c.chunkSize)
let read = await c.reader(cast[ChunkBuffer](addr buff[0]), buff.len)
if read <= 0:
return @[]
c.offset += read
if not c.pad and buff.len > read:
buff.setLen(read)
return move buff
func new*(
T: type Chunker,
reader: Reader,
chunkSize = DefaultChunkSize,
pad = true
): Chunker =
## create a new Chunker instance
##
Chunker(
reader: reader,
offset: 0,
chunkSize: chunkSize,
pad: pad)
proc new*(
T: type LPStreamChunker,
stream: LPStream,
chunkSize = DefaultChunkSize,
pad = true
): LPStreamChunker =
## create the default File chunker
##
proc reader(data: ChunkBuffer, len: int): Future[int]
{.gcsafe, async, raises: [Defect].} =
var res = 0
try:
while res < len:
res += await stream.readOnce(addr data[res], len - res)
except LPStreamEOFError as exc:
trace "LPStreamChunker stream Eof", exc = exc.msg
except CatchableError as exc:
trace "CatchableError exception", exc = exc.msg
raise newException(Defect, exc.msg)
return res
LPStreamChunker.new(
reader = reader,
chunkSize = chunkSize,
pad = pad)
proc new*(
T: type FileChunker,
file: File,
chunkSize = DefaultChunkSize,
pad = true
): FileChunker =
## create the default File chunker
##
proc reader(data: ChunkBuffer, len: int): Future[int]
{.gcsafe, async, raises: [Defect].} =
var total = 0
try:
while total < len:
let res = file.readBuffer(addr data[total], len - total)
if res <= 0:
break
total += res
except IOError as exc:
trace "Exception reading file", exc = exc.msg
except CatchableError as exc:
trace "CatchableError exception", exc = exc.msg
raise newException(Defect, exc.msg)
return total
FileChunker.new(
reader = reader,
chunkSize = chunkSize,
pad = pad)