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adding bufferred stream

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Dmitriy Ryajov 2019-09-01 15:51:39 -06:00
parent cbf0f4f186
commit fceea14aa5
2 changed files with 411 additions and 0 deletions
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libp2p/stream/bufferstream.nim Normal file
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## Nim-LibP2P
## Copyright (c) 2018 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 deques, tables, sequtils, math
import chronos
import ../stream/lpstream
## I use a dequeu here because it uses a ring buffer under the hood
## which should on average be more performant than memMoves and copies
type
WriteHandler* = proc (data: seq[byte]) {.gcsafe.} # TODO: figure out how to make this generic to avoid casts
BufferStream* = ref object of LPStream
maxSize*: int
readBuf: Deque[byte] # a deque is based on a ring buffer
readReqs: Deque[Future[int]] # use dequeue to fire reads in order
dataReadEvent: AsyncEvent
writeHandler: WriteHandler
proc requestReadBytes(s: BufferStream): Future[int] =
## create a future that will complete when more
## data becomes available in the read buffer
result = newFuture[int]()
s.readReqs.addLast(result)
proc newBufferStream*(handler: WriteHandler, size: int = 1024): BufferStream =
new result
result.maxSize = if isPowerOfTwo(size): size else: nextPowerOfTwo(size)
result.readBuf = initDeque[byte](result.maxSize)
result.readReqs = initDeque[Future[int]]()
result.dataReadEvent = newAsyncEvent()
result.writeHandler = handler
proc popFirst*(s: BufferStream): byte =
result = s.readBuf.popFirst()
s.dataReadEvent.fire()
proc popLast*(s: BufferStream): byte =
result = s.readBuf.popLast()
s.dataReadEvent.fire()
proc shrink(s: BufferStream, fromFirst = 0, fromLast = 0) =
s.readBuf.shrink(fromFirst, fromLast)
s.dataReadEvent.fire()
proc len*(s: BufferStream): int = s.readBuf.len
proc pushTo*(s: BufferStream, data: seq[byte]) {.async, gcsafe.} =
## Write bytes to internal read buffer, use this to fill up the
## buffer with data.
##
## This method is async and will wait until all data has been
## written to the internal buffer; this is done so that backpressure
## is preserved.
var index = 0
while true:
while index < data.len and s.readBuf.len < s.maxSize:
s.readBuf.addLast(data[index])
inc(index)
# resolve the next queued read request
if s.readReqs.len > 0:
s.readReqs.popFirst().complete(index + 1)
if index >= data.len:
break
# if we couldn't transfer all the data to the
# internal buf do an async sleep and try writting
# some more, this should preserve backpresure
await s.dataReadEvent.wait()
method read*(s: BufferStream, n = -1): Future[seq[byte]] {.async, gcsafe.} =
## Read all bytes (n <= 0) or exactly `n` bytes from buffer
##
## This procedure allocates buffer seq[byte] and return it as result.
var size = if n > 0: n else: s.readBuf.len()
var index = 0
while index < size:
while s.readBuf.len() > 0 and index < size:
result.add(s.popFirst())
inc(index)
if index < size:
discard await s.requestReadBytes()
method readExactly*(s: BufferStream, pbytes: pointer, nbytes: int): Future[void] {.async, gcsafe.} =
## Read exactly ``nbytes`` bytes from read-only stream ``rstream`` and store
## it to ``pbytes``.
##
## If EOF is received and ``nbytes`` is not yet readed, the procedure
## will raise ``LPStreamIncompleteError``.
if nbytes > s.readBuf.len():
raise newLPStreamIncompleteError()
let buff = await s.read(nbytes)
copyMem(pbytes, unsafeAddr buff[0], nbytes)
method readLine*(s: BufferStream, limit = 0, sep = "\r\n"): Future[string] {.async, gcsafe.} =
## Read one line from read-only stream ``rstream``, where ``"line"`` is a
## sequence of bytes ending with ``sep`` (default is ``"\r\n"``).
##
## If EOF is received, and ``sep`` was not found, the method will return the
## partial read bytes.
##
## If the EOF was received and the internal buffer is empty, return an
## empty string.
##
## If ``limit`` more then 0, then result string will be limited to ``limit``
## bytes.
result = ""
var lim = if limit <= 0: -1 else: limit
var state = 0
var index = 0
index = 0
while index < s.readBuf.len:
let ch = char(s.readBuf[index])
if sep[state] == ch:
inc(state)
if state == len(sep):
s.shrink(index + 1)
break
else:
state = 0
result.add(ch)
if len(result) == lim:
s.shrink(index + 1)
break
inc(index)
method readOnce*(s: BufferStream, pbytes: pointer, nbytes: int): Future[int] {.async, gcsafe.} =
## Perform one read operation on read-only stream ``rstream``.
##
## If internal buffer is not empty, ``nbytes`` bytes will be transferred from
## internal buffer, otherwise it will wait until some bytes will be received.
if s.readBuf.len == 0:
discard await s.requestReadBytes()
var len = if nbytes > s.readBuf.len: s.readBuf.len else: nbytes
await s.readExactly(pbytes, len)
result = len
method readUntil*(s: BufferStream,
pbytes: pointer,
nbytes: int,
sep: seq[byte]):
Future[int] {.async, gcsafe.} =
## Read data from the read-only stream ``rstream`` until separator ``sep`` is
## found.
##
## On success, the data and separator will be removed from the internal
## buffer (consumed). Returned data will include the separator at the end.
##
## If EOF is received, and `sep` was not found, procedure will raise
## ``LPStreamIncompleteError``.
##
## If ``nbytes`` bytes has been received and `sep` was not found, procedure
## will raise ``LPStreamLimitError``.
##
## Procedure returns actual number of bytes read.
var
dest = cast[ptr UncheckedArray[byte]](pbytes)
state = 0
k = 0
let datalen = s.readBuf.len()
if datalen == 0 and s.readBuf.len() == 0:
raise newLPStreamIncompleteError()
var index = 0
while index < datalen:
let ch = s.readBuf[index]
if sep[state] == ch:
inc(state)
else:
state = 0
if k < nbytes:
dest[k] = ch
inc(k)
else:
raise newLPStreamLimitError()
if state == len(sep):
break
inc(index)
if state == len(sep):
s.shrink(index + 1)
result = k
else:
s.shrink(datalen)
method write*(s: BufferStream, pbytes: pointer, nbytes: int) {.async, gcsafe.} =
var buf: seq[byte] = newSeq[byte](nbytes)
copyMem(addr buf[0], pbytes, nbytes)
s.writeHandler(buf)
method write*(s: BufferStream, msg: string, msglen = -1) {.async, gcsafe.} =
var buf = ""
shallowCopy(buf, if msglen > 0: msg[0..<msglen] else: msg)
s.writeHandler(cast[seq[byte]](toSeq(buf.items)))
method write*(s: BufferStream, msg: seq[byte], msglen = -1) {.async, gcsafe.} =
var buf: seq[byte]
shallowCopy(buf, if msglen > 0: msg[0..<msglen] else: msg)
s.writeHandler(buf)
method close*(s: BufferStream) {.async, gcsafe.} =
for r in s.readReqs:
r.cancel()
s.readBuf.clear()
s.closed = true

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import unittest, deques, sequtils
import chronos
import ../libp2p/stream/bufferstream
suite "BufferStream":
test "push data to buffer":
proc testPushTo(): Future[bool] {.async.} =
proc writeHandler(data: seq[byte]) = discard
let buff = newBufferStream(writeHandler, 16)
check buff.len == 0
var data: seq[char]
data.add(@"12345")
await buff.pushTo(cast[seq[byte]](data))
check buff.len == 5
result = true
check:
waitFor(testPushTo()) == true
test "push and wait":
proc testPushTo(): Future[bool] {.async.} =
proc writeHandler(data: seq[byte]) = discard
let buff = newBufferStream(writeHandler, 4)
check buff.len == 0
let fut = buff.pushTo(cast[seq[byte]](@"12345"))
check buff.len == 4
check buff.popFirst() == byte(ord('1'))
await fut
check buff.len == 4
result = true
check:
waitFor(testPushTo()) == true
test "read":
proc testRead(): Future[bool] {.async.} =
proc writeHandler(data: seq[byte]) = discard
let buff = newBufferStream(writeHandler, 10)
check buff.len == 0
await buff.pushTo(cast[seq[byte]](@"12345"))
check @"12345" == cast[string](await buff.read())
result = true
check:
waitFor(testRead()) == true
test "read with size":
proc testRead(): Future[bool] {.async.} =
proc writeHandler(data: seq[byte]) = discard
let buff = newBufferStream(writeHandler, 10)
check buff.len == 0
await buff.pushTo(cast[seq[byte]](@"12345"))
let data = cast[string](await buff.read(3))
check ['1', '2', '3'] == data
result = true
check:
waitFor(testRead()) == true
test "read and wait":
proc testRead(): Future[bool] {.async.} =
proc writeHandler(data: seq[byte]) = discard
let buff = newBufferStream(writeHandler, 10)
check buff.len == 0
await buff.pushTo(cast[seq[byte]](@"123"))
check buff.len == 3
let readFut = buff.read(5)
await buff.pushTo(cast[seq[byte]](@"45"))
check buff.len == 2
check cast[string](await readFut) == ['1', '2', '3', '4', '5']
result = true
check:
waitFor(testRead()) == true
test "readExactly":
proc testReadExactly(): Future[bool] {.async.} =
proc writeHandler(data: seq[byte]) = discard
let buff = newBufferStream(writeHandler, 10)
check buff.len == 0
await buff.pushTo(cast[seq[byte]](@"12345"))
check buff.len == 5
var data: seq[byte] = newSeq[byte](2)
await buff.readExactly(addr data[0], 2)
check cast[string](data) == @['1', '2']
result = true
check:
waitFor(testReadExactly()) == true
test "readLine":
proc testReadLine(): Future[bool] {.async.} =
proc writeHandler(data: seq[byte]) = discard
let buff = newBufferStream(writeHandler, 16)
check buff.len == 0
await buff.pushTo(cast[seq[byte]](@"12345\n67890"))
check buff.len == 11
check "12345" == await buff.readLine(0, "\n")
result = true
check:
waitFor(testReadLine()) == true
test "readOnce":
proc testReadOnce(): Future[bool] {.async.} =
proc writeHandler(data: seq[byte]) = discard
let buff = newBufferStream(writeHandler, 10)
check buff.len == 0
var data: seq[byte] = newSeq[byte](3)
let readFut = buff.readOnce(addr data[0], 5)
await buff.pushTo(cast[seq[byte]](@"123"))
check buff.len == 3
check (await readFut) == 3
check cast[string](data) == @['1', '2', '3']
result = true
check:
waitFor(testReadOnce()) == true
test "readUntil":
proc testReadUntil(): Future[bool] {.async.} =
proc writeHandler(data: seq[byte]) = discard
let buff = newBufferStream(writeHandler, 10)
check buff.len == 0
var data: seq[byte] = newSeq[byte](3)
await buff.pushTo(cast[seq[byte]](@"123$45"))
check buff.len == 6
let readFut = buff.readUntil(addr data[0], 5, @[byte('$')])
check (await readFut) == 4
check cast[string](data) == @['1', '2', '3']
result = true
check:
waitFor(testReadUntil()) == true
test "write ptr":
proc testWritePtr(): Future[bool] {.async.} =
proc writeHandler(data: seq[byte]) =
check cast[string](data) == "Hello!"
let buff = newBufferStream(writeHandler, 10)
check buff.len == 0
var data = "Hello!"
await buff.write(addr data[0], data.len)
result = true
check:
waitFor(testWritePtr()) == true
test "write string":
proc testWritePtr(): Future[bool] {.async.} =
proc writeHandler(data: seq[byte]) =
check cast[string](data) == "Hello!"
let buff = newBufferStream(writeHandler, 10)
check buff.len == 0
await buff.write("Hello!", 6)
result = true
check:
waitFor(testWritePtr()) == true
test "write bytes":
proc testWritePtr(): Future[bool] {.async.} =
proc writeHandler(data: seq[byte]) =
check cast[string](data) == "Hello!"
let buff = newBufferStream(writeHandler, 10)
check buff.len == 0
await buff.write(cast[seq[byte]](toSeq("Hello!".items)), 6)
result = true
check:
waitFor(testWritePtr()) == true