nim-libp2p/libp2p/muxers/mplex/coder.nim

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## Nim-LibP2P
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## Copyright (c) 2019 Status Research & Development GmbH
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## 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.
{.push raises: [Defect].}
import chronos
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import nimcrypto/utils, chronicles, stew/byteutils
import ../../stream/connection,
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../../utility,
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../../varint,
../../vbuffer,
../muxer
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logScope:
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topics = "libp2p mplexcoder"
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type
MessageType* {.pure.} = enum
New,
MsgIn,
MsgOut,
CloseIn,
CloseOut,
ResetIn,
ResetOut
Msg* = tuple
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id: uint64
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msgType: MessageType
data: seq[byte]
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InvalidMplexMsgType* = object of MuxerError
# https://github.com/libp2p/specs/tree/master/mplex#writing-to-a-stream
const MaxMsgSize* = 1 shl 20 # 1mb
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proc newInvalidMplexMsgType(): ref InvalidMplexMsgType =
newException(InvalidMplexMsgType, "invalid message type")
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proc readMsg*(conn: Connection): Future[Msg] {.async, gcsafe.} =
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let header = await conn.readVarint()
trace "read header varint", varint = header, conn
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let data = await conn.readLp(MaxMsgSize)
trace "read data", dataLen = data.len, data = shortLog(data), conn
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let msgType = header and 0x7
if msgType.int > ord(MessageType.ResetOut):
raise newInvalidMplexMsgType()
return (header shr 3, MessageType(msgType), data)
proc writeMsg*(conn: Connection,
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id: uint64,
msgType: MessageType,
data: seq[byte] = @[]): Future[void] =
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var
left = data.len
offset = 0
buf = initVBuffer()
# Split message into length-prefixed chunks
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while left > 0 or data.len == 0:
let
chunkSize = if left > MaxMsgSize: MaxMsgSize - 64 else: left
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buf.writePBVarint(id shl 3 or ord(msgType).uint64)
buf.writeSeq(data.toOpenArray(offset, offset + chunkSize - 1))
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left = left - chunkSize
offset = offset + chunkSize
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if data.len == 0:
break
trace "writing mplex message",
conn, id, msgType, data = data.len, encoded = buf.buffer.len
# Write all chunks in a single write to avoid async races where a close
# message gets written before some of the chunks
conn.write(buf.buffer)
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proc writeMsg*(conn: Connection,
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id: uint64,
msgType: MessageType,
data: string): Future[void] =
conn.writeMsg(id, msgType, data.toBytes())