Safe Haskell	None
Language	Haskell2010

Network.Wai.Handler.Warp.Internal

Contents

Settings
Low level run functions
Connection
Version
Data types
Time out manager
File descriptor cache
File information cache
Date
Request and response
Platform dependent helper functions
Misc

Synopsis

data Settings = Settings {
- settingsPort :: Port
- settingsHost :: HostPreference
- settingsOnException :: Maybe Request -> SomeException -> IO ()
- settingsOnExceptionResponse :: SomeException -> Response
- settingsOnOpen :: SockAddr -> IO Bool
- settingsOnClose :: SockAddr -> IO ()
- settingsTimeout :: Int
- settingsManager :: Maybe Manager
- settingsFdCacheDuration :: Int
- settingsFileInfoCacheDuration :: Int
- settingsBeforeMainLoop :: IO ()
- settingsFork :: ((forall a. IO a -> IO a) -> IO ()) -> IO ()
- settingsNoParsePath :: Bool
- settingsInstallShutdownHandler :: IO () -> IO ()
- settingsServerName :: ByteString
- settingsMaximumBodyFlush :: Maybe Int
- settingsProxyProtocol :: ProxyProtocol
- settingsSlowlorisSize :: Int
- settingsHTTP2Enabled :: Bool
- settingsLogger :: Request -> Status -> Maybe Integer -> IO ()
- settingsServerPushLogger :: Request -> ByteString -> Integer -> IO ()
- settingsGracefulShutdownTimeout :: Maybe Int
- settingsGracefulCloseTimeout1 :: Int
- settingsGracefulCloseTimeout2 :: Int
- settingsMaxTotalHeaderLength :: Int
- settingsAltSvc :: Maybe ByteString
}
data ProxyProtocol
- = ProxyProtocolNone
- | ProxyProtocolRequired
- | ProxyProtocolOptional
runSettingsConnection :: Settings -> IO (Connection, SockAddr) -> Application -> IO ()
runSettingsConnectionMaker :: Settings -> IO (IO Connection, SockAddr) -> Application -> IO ()
runSettingsConnectionMakerSecure :: Settings -> IO (IO (Connection, Transport), SockAddr) -> Application -> IO ()
data Transport
- = TCP
- | TLS {
  - tlsMajorVersion :: Int
  - tlsMinorVersion :: Int
  - tlsNegotiatedProtocol :: Maybe ByteString
  - tlsChiperID :: Word16
  - tlsClientCertificate :: Maybe CertificateChain
  }
- | QUIC {
  }
data Connection = Connection {
- connSendMany :: [ByteString] -> IO ()
- connSendAll :: ByteString -> IO ()
- connSendFile :: SendFile
- connClose :: IO ()
- connFree :: IO ()
- connRecv :: Recv
- connRecvBuf :: RecvBuf
- connWriteBuffer :: Buffer
- connBufferSize :: BufSize
- connHTTP2 :: IORef Bool
}
socketConnection :: Settings -> Socket -> IO Connection
type Recv = IO ByteString
type RecvBuf = Buffer -> BufSize -> IO Bool
makePlainReceiveN :: Socket -> ByteString -> IO (BufSize -> IO ByteString)
type Buffer = Ptr Word8
type BufSize = Int
bufferSize :: BufSize
allocateBuffer :: Int -> IO Buffer
freeBuffer :: Buffer -> IO ()
copy :: Buffer -> ByteString -> IO Buffer
data FileId = FileId {
- fileIdPath :: FilePath
- fileIdFd :: Maybe Fd
}
type SendFile = FileId -> Integer -> Integer -> IO () -> [ByteString] -> IO ()
sendFile :: Socket -> Buffer -> BufSize -> (ByteString -> IO ()) -> SendFile
readSendFile :: Buffer -> BufSize -> (ByteString -> IO ()) -> SendFile
warpVersion :: String
data InternalInfo = InternalInfo {
- timeoutManager :: Manager
- getDate :: IO GMTDate
- getFd :: FilePath -> IO (Maybe Fd, Refresh)
- getFileInfo :: FilePath -> IO FileInfo
}
type HeaderValue = ByteString
type IndexedHeader = Array Int (Maybe HeaderValue)
requestMaxIndex :: Int
module System.TimeManager
withFdCache :: Int -> ((FilePath -> IO (Maybe Fd, Refresh)) -> IO a) -> IO a
data Fd
type Refresh = IO ()
openFile :: FilePath -> IO Fd
closeFile :: Fd -> IO ()
setFileCloseOnExec :: Fd -> IO ()
data FileInfo = FileInfo {
- fileInfoName :: !FilePath
- fileInfoSize :: !Integer
- fileInfoTime :: HTTPDate
- fileInfoDate :: ByteString
}
withFileInfoCache :: Int -> ((FilePath -> IO FileInfo) -> IO a) -> IO a
getInfo :: FilePath -> IO FileInfo
withDateCache :: (IO GMTDate -> IO a) -> IO a
type GMTDate = ByteString
data Source
recvRequest :: Bool -> Settings -> Connection -> InternalInfo -> Handle -> SockAddr -> Source -> Transport -> IO (Request, Maybe (IORef Int), IndexedHeader, IO ByteString)
sendResponse :: Settings -> Connection -> InternalInfo -> Handle -> Request -> IndexedHeader -> IO ByteString -> Response -> IO Bool
setSocketCloseOnExec :: Socket -> IO ()
windowsThreadBlockHack :: IO a -> IO a
http2server :: Settings -> InternalInfo -> Transport -> SockAddr -> Application -> Server
withII :: Settings -> (InternalInfo -> IO a) -> IO a
pReadMaker :: InternalInfo -> PositionReadMaker

Settings

data Settings Source #

Various Warp server settings. This is purposely kept as an abstract data type so that new settings can be added without breaking backwards compatibility. In order to create a Settings value, use defaultSettings and the various 'set' functions to modify individual fields. For example:

setTimeout 20 defaultSettings

Constructors

Settings

Fields

settingsPort :: Port
Port to listen on. Default value: 3000
settingsHost :: HostPreference
Default value: HostIPv4
settingsOnException :: Maybe Request -> SomeException -> IO ()
What to do with exceptions thrown by either the application or server. Default: ignore server-generated exceptions (see InvalidRequest) and print application-generated applications to stderr.
settingsOnExceptionResponse :: SomeException -> Response
A function to create Response when an exception occurs.
Default: 500, text/plain, "Something went wrong"
Since 2.0.3
settingsOnOpen :: SockAddr -> IO Bool
What to do when a connection is open. When False is returned, the connection is closed immediately. Otherwise, the connection is going on. Default: always returns True.
settingsOnClose :: SockAddr -> IO ()
What to do when a connection is close. Default: do nothing.
settingsTimeout :: Int
Timeout value in seconds. Default value: 30
settingsManager :: Maybe Manager
Use an existing timeout manager instead of spawning a new one. If used, settingsTimeout is ignored. Default is Nothing
settingsFdCacheDuration :: Int
Cache duration time of file descriptors in seconds. 0 means that the cache mechanism is not used. Default value: 0
settingsFileInfoCacheDuration :: Int
Cache duration time of file information in seconds. 0 means that the cache mechanism is not used. Default value: 0
settingsBeforeMainLoop :: IO ()
Code to run after the listening socket is ready but before entering the main event loop. Useful for signaling to tests that they can start running, or to drop permissions after binding to a restricted port.
Default: do nothing.
Since 1.3.6
settingsFork :: ((forall a. IO a -> IO a) -> IO ()) -> IO ()
Code to fork a new thread to accept a connection.
This may be useful if you need OS bound threads, or if you wish to develop an alternative threading model.
Default: void . forkIOWithUnmask
Since 3.0.4
settingsNoParsePath :: Bool
Perform no parsing on the rawPathInfo.
This is useful for writing HTTP proxies.
Default: False
Since 2.0.3
settingsInstallShutdownHandler :: IO () -> IO ()
An action to install a handler (e.g. Unix signal handler) to close a listen socket. The first argument is an action to close the listen socket.
Default: no action
Since 3.0.1
settingsServerName :: ByteString
Default server name if application does not set one.
Since 3.0.2
settingsMaximumBodyFlush :: Maybe Int
See setMaximumBodyFlush.
Since 3.0.3
settingsProxyProtocol :: ProxyProtocol
Specify usage of the PROXY protocol.
Since 3.0.5
settingsSlowlorisSize :: Int
Size of bytes read to prevent Slowloris protection. Default value: 2048
Since 3.1.2
settingsHTTP2Enabled :: Bool
Whether to enable HTTP2 ALPN/upgrades. Default: True
Since 3.1.7
settingsLogger :: Request -> Status -> Maybe Integer -> IO ()
A log function. Default: no action.
Since 3.1.10
settingsServerPushLogger :: Request -> ByteString -> Integer -> IO ()
A HTTP/2 server push log function. Default: no action.
Since 3.2.7
settingsGracefulShutdownTimeout :: Maybe Int
An optional timeout to limit the time (in seconds) waiting for a graceful shutdown of the web server.
Since 3.2.8
settingsGracefulCloseTimeout1 :: Int
A timeout to limit the time (in milliseconds) waiting for FIN for HTTP/1.x. 0 means uses immediate close. Default: 0.
Since 3.3.5
settingsGracefulCloseTimeout2 :: Int
A timeout to limit the time (in milliseconds) waiting for FIN for HTTP/2. 0 means uses immediate close. Default: 2000.
Since 3.3.5
settingsMaxTotalHeaderLength :: Int
Determines the maximum header size that Warp will tolerate when using HTTP/1.x.
Since 3.3.8
settingsAltSvc :: Maybe ByteString
Specify the header value of Alternative Services (AltSvc:).
Default: Nothing
Since 3.3.11

data ProxyProtocol Source #

Specify usage of the PROXY protocol.

Constructors

ProxyProtocolNone	See `setProxyProtocolNone`.
ProxyProtocolRequired	See `setProxyProtocolRequired`.
ProxyProtocolOptional	See `setProxyProtocolOptional`.

Low level run functions

runSettingsConnection :: Settings -> IO (Connection, SockAddr) -> Application -> IO () Source #

The connection setup action would be expensive. A good example is initialization of TLS. So, this converts the connection setup action to the connection maker which will be executed after forking a new worker thread. Then this calls runSettingsConnectionMaker with the connection maker. This allows the expensive computations to be performed in a separate worker thread instead of the main server loop.

Since 1.3.5

runSettingsConnectionMaker :: Settings -> IO (IO Connection, SockAddr) -> Application -> IO () Source #

This modifies the connection maker so that it returns TCP for Transport (i.e. plain HTTP) then calls runSettingsConnectionMakerSecure.

runSettingsConnectionMakerSecure :: Settings -> IO (IO (Connection, Transport), SockAddr) -> Application -> IO () Source #

The core run function which takes Settings, a connection maker and Application. The connection maker can return a connection of either plain HTTP or HTTP over TLS.

Since 2.1.4

data Transport Source #

What kind of transport is used for this connection?

Constructors

TCP	Plain channel: TCP
TLS	Encrypted channel: TLS or SSL
Fields tlsMajorVersion :: Int tlsMinorVersion :: Int tlsNegotiatedProtocol :: Maybe ByteString The result of Application Layer Protocol Negociation in RFC 7301 tlsChiperID :: Word16 tlsClientCertificate :: Maybe CertificateChain
QUIC
Fields quicNegotiatedProtocol :: Maybe ByteString quicChiperID :: Word16 quicClientCertificate :: Maybe CertificateChain

Connection

data Connection Source #

Data type to manipulate IO actions for connections. This is used to abstract IO actions for plain HTTP and HTTP over TLS.

Constructors

Connection

Fields

connSendMany :: [ByteString] -> IO ()
This is not used at this moment.
connSendAll :: ByteString -> IO ()
The sending function.
connSendFile :: SendFile
The sending function for files in HTTP/1.1.
connClose :: IO ()
The connection closing function. Warp guarantees it will only be called once. Other functions (like connRecv) may be called after connClose is called.
connFree :: IO ()
Free any buffers allocated. Warp guarantees it will only be called once, and no other functions will be called after it.
connRecv :: Recv
The connection receiving function. This returns "" for EOF.
connRecvBuf :: RecvBuf
The connection receiving function. This tries to fill the buffer. This returns when the buffer is filled or reaches EOF.
connWriteBuffer :: Buffer
The write buffer.
connBufferSize :: BufSize
The size of the write buffer.
connHTTP2 :: IORef Bool
Is this connection HTTP/2?

socketConnection :: Settings -> Socket -> IO Connection Source #

Creating Connection for plain HTTP based on a given socket.

Receive

type Recv = IO ByteString Source #

Type for the action to receive input data

type RecvBuf = Buffer -> BufSize -> IO Bool Source #

Type for the action to receive input data with a buffer. The result boolean indicates whether or not the buffer is fully filled.

makePlainReceiveN :: Socket -> ByteString -> IO (BufSize -> IO ByteString) Source #

This function returns a receiving function based on two receiving functions. The returned function efficiently manages received data which is initialized by the first argument. The returned function may allocate a byte string with malloc().

Buffer

type Buffer = Ptr Word8 Source #

Type for buffer

type BufSize = Int Source #

Type for buffer size

bufferSize :: BufSize Source #

The default size of the write buffer: 16384 (2^14 = 1024 * 16). This is the maximum size of TLS record. This is also the maximum size of HTTP/2 frame payload (excluding frame header).

allocateBuffer :: Int -> IO Buffer Source #

Allocating a buffer with malloc().

freeBuffer :: Buffer -> IO () Source #

Releasing a buffer with free().

copy :: Buffer -> ByteString -> IO Buffer Source #

Copying the bytestring to the buffer. This function returns the point where the next copy should start.

Sendfile

data FileId Source #

Data type to abstract file identifiers. On Unix, a file descriptor would be specified to make use of the file descriptor cache.

Since: 3.1.0

Constructors

FileId
Fields fileIdPath :: FilePath fileIdFd :: Maybe Fd

type SendFile = FileId -> Integer -> Integer -> IO () -> [ByteString] -> IO () Source #

fileid, offset, length, hook action, HTTP headers

Since: 3.1.0

sendFile :: Socket -> Buffer -> BufSize -> (ByteString -> IO ()) -> SendFile Source #

Function to send a file based on sendfile() for Linux/Mac/FreeBSD. This makes use of the file descriptor cache. For other OSes, this is identical to readSendFile.

Since: 3.1.0

readSendFile :: Buffer -> BufSize -> (ByteString -> IO ()) -> SendFile Source #

Function to send a file based on pread()/send() for Unix. This makes use of the file descriptor cache. For Windows, this is emulated by Handle.

Since: 3.1.0

Version

warpVersion :: String Source #

The version of Warp.

Data types

data InternalInfo Source #

Constructors

InternalInfo
Fields timeoutManager :: Manager getDate :: IO GMTDate getFd :: FilePath -> IO (Maybe Fd, Refresh) getFileInfo :: FilePath -> IO FileInfo

type HeaderValue = ByteString Source #

The type for header value used with HeaderName.

type IndexedHeader = Array Int (Maybe HeaderValue) Source #

Array for a set of HTTP headers.

requestMaxIndex :: Int Source #

The size for IndexedHeader for HTTP Request. From 0 to this corresponds to "Content-Length", "Transfer-Encoding", "Expect", "Connection", "Range", "Host", "If-Modified-Since", "If-Unmodified-Since" and "If-Range".

Time out manager

In order to provide slowloris protection, Warp provides timeout handlers. We follow these rules:

A timeout is created when a connection is opened.
When all request headers are read, the timeout is tickled.
Every time at least the slowloris size settings number of bytes of the request body are read, the timeout is tickled.
The timeout is paused while executing user code. This will apply to both the application itself, and a ResponseSource response. The timeout is resumed as soon as we return from user code.
Every time data is successfully sent to the client, the timeout is tickled.

module System.TimeManager

File descriptor cache

withFdCache :: Int -> ((FilePath -> IO (Maybe Fd, Refresh)) -> IO a) -> IO a Source #

Creating MutableFdCache and executing the action in the second argument. The first argument is a cache duration in second.

data Fd #

Instances

Bounded Fd
Instance details Defined in System.Posix.Types Methods minBound :: Fd # maxBound :: Fd #
Enum Fd
Instance details Defined in System.Posix.Types Methods succ :: Fd -> Fd # pred :: Fd -> Fd # toEnum :: Int -> Fd # fromEnum :: Fd -> Int # enumFrom :: Fd -> [Fd] # enumFromThen :: Fd -> Fd -> [Fd] # enumFromTo :: Fd -> Fd -> [Fd] # enumFromThenTo :: Fd -> Fd -> Fd -> [Fd] #
Eq Fd
Instance details Defined in System.Posix.Types Methods (==) :: Fd -> Fd -> Bool # (/=) :: Fd -> Fd -> Bool #
Integral Fd
Instance details Defined in System.Posix.Types Methods quot :: Fd -> Fd -> Fd # rem :: Fd -> Fd -> Fd # div :: Fd -> Fd -> Fd # mod :: Fd -> Fd -> Fd # quotRem :: Fd -> Fd -> (Fd, Fd) # divMod :: Fd -> Fd -> (Fd, Fd) # toInteger :: Fd -> Integer #
Num Fd
Instance details Defined in System.Posix.Types Methods (+) :: Fd -> Fd -> Fd # (-) :: Fd -> Fd -> Fd # (*) :: Fd -> Fd -> Fd # negate :: Fd -> Fd # abs :: Fd -> Fd # signum :: Fd -> Fd # fromInteger :: Integer -> Fd #
Ord Fd
Instance details Defined in System.Posix.Types Methods compare :: Fd -> Fd -> Ordering # (<) :: Fd -> Fd -> Bool # (<=) :: Fd -> Fd -> Bool # (>) :: Fd -> Fd -> Bool # (>=) :: Fd -> Fd -> Bool # max :: Fd -> Fd -> Fd # min :: Fd -> Fd -> Fd #
Read Fd
Instance details Defined in System.Posix.Types Methods readsPrec :: Int -> ReadS Fd # readList :: ReadS [Fd] # readPrec :: ReadPrec Fd # readListPrec :: ReadPrec [Fd] #
Real Fd
Instance details Defined in System.Posix.Types Methods toRational :: Fd -> Rational #
Show Fd
Instance details Defined in System.Posix.Types Methods showsPrec :: Int -> Fd -> ShowS # show :: Fd -> String # showList :: [Fd] -> ShowS #
Storable Fd
Instance details Defined in System.Posix.Types Methods sizeOf :: Fd -> Int # alignment :: Fd -> Int # peekElemOff :: Ptr Fd -> Int -> IO Fd # pokeElemOff :: Ptr Fd -> Int -> Fd -> IO () # peekByteOff :: Ptr b -> Int -> IO Fd # pokeByteOff :: Ptr b -> Int -> Fd -> IO () # peek :: Ptr Fd -> IO Fd # poke :: Ptr Fd -> Fd -> IO () #
Bits Fd
Instance details Defined in System.Posix.Types Methods (.&.) :: Fd -> Fd -> Fd # (.\|.) :: Fd -> Fd -> Fd # xor :: Fd -> Fd -> Fd # complement :: Fd -> Fd # shift :: Fd -> Int -> Fd # rotate :: Fd -> Int -> Fd # zeroBits :: Fd # bit :: Int -> Fd # setBit :: Fd -> Int -> Fd # clearBit :: Fd -> Int -> Fd # complementBit :: Fd -> Int -> Fd # testBit :: Fd -> Int -> Bool # bitSizeMaybe :: Fd -> Maybe Int # bitSize :: Fd -> Int # isSigned :: Fd -> Bool # shiftL :: Fd -> Int -> Fd # unsafeShiftL :: Fd -> Int -> Fd # shiftR :: Fd -> Int -> Fd # unsafeShiftR :: Fd -> Int -> Fd # rotateL :: Fd -> Int -> Fd # rotateR :: Fd -> Int -> Fd # popCount :: Fd -> Int #
FiniteBits Fd
Instance details Defined in System.Posix.Types Methods finiteBitSize :: Fd -> Int # countLeadingZeros :: Fd -> Int # countTrailingZeros :: Fd -> Int #

type Refresh = IO () Source #

An action to activate a Fd cache entry.

openFile :: FilePath -> IO Fd Source #

closeFile :: Fd -> IO () Source #

setFileCloseOnExec :: Fd -> IO () Source #

File information cache

data FileInfo Source #

File information.

Constructors

FileInfo
Fields fileInfoName :: !FilePath fileInfoSize :: !Integer fileInfoTime :: HTTPDate Modification time fileInfoDate :: ByteString Modification time in the GMT format

Instances

Eq FileInfo Source #
Instance details Defined in Network.Wai.Handler.Warp.FileInfoCache Methods (==) :: FileInfo -> FileInfo -> Bool # (/=) :: FileInfo -> FileInfo -> Bool #
Show FileInfo Source #
Instance details Defined in Network.Wai.Handler.Warp.FileInfoCache Methods showsPrec :: Int -> FileInfo -> ShowS # show :: FileInfo -> String # showList :: [FileInfo] -> ShowS #

withFileInfoCache :: Int -> ((FilePath -> IO FileInfo) -> IO a) -> IO a Source #

Creating a file information cache and executing the action in the second argument. The first argument is a cache duration in second.

getInfo :: FilePath -> IO FileInfo Source #

Getting the file information corresponding to the file.

Date

withDateCache :: (IO GMTDate -> IO a) -> IO a Source #

Creating DateCache and executing the action.

type GMTDate = ByteString Source #

The type of the Date header value.

Request and response

data Source Source #

Type for input streaming.

recvRequest Source #

Arguments

:: Bool	first request on this connection?
-> Settings
-> Connection
-> InternalInfo
-> Handle
-> SockAddr	Peer's address.
-> Source	Where HTTP request comes from.
-> Transport
-> IO (Request, Maybe (IORef Int), IndexedHeader, IO ByteString)	`Request` passed to `Application`, how many bytes remain to be consumed, if known `IndexedHeader` of HTTP request for internal use, Body producing action used for flushing the request body

Receiving a HTTP request from Connection and parsing its header to create Request.

sendResponse Source #

Arguments

:: Settings
-> Connection
-> InternalInfo
-> Handle
-> Request	HTTP request.
-> IndexedHeader	Indexed header of HTTP request.
-> IO ByteString	source from client, for raw response
-> Response	HTTP response including status code and response header.
-> IO Bool	Returing True if the connection is persistent.

Sending a HTTP response to Connection according to Response.

Applications/middlewares MUST provide a proper ResponseHeaders. so that inconsistency does not happen. No header is deleted by this function.

Especially, Applications/middlewares MUST provide a proper Content-Type. They MUST NOT provide Content-Length, Content-Range, and Transfer-Encoding because they are inserted, when necessary, regardless they already exist. This function does not insert Content-Encoding. It's middleware's responsibility.

The Date and Server header is added if not exist in HTTP response header.

There are three basic APIs to create Response:

responseBuilder :: Status -> ResponseHeaders -> Builder -> Response: HTTP response body is created from Builder. Transfer-Encoding: chunked is used in HTTP/1.1.
responseStream :: Status -> ResponseHeaders -> StreamingBody -> Response: HTTP response body is created from Builder. Transfer-Encoding: chunked is used in HTTP/1.1.
responseRaw :: (IO ByteString -> (ByteString -> IO ()) -> IO ()) -> Response -> Response: No header is added and no Transfer-Encoding: is applied.
responseFile :: Status -> ResponseHeaders -> FilePath -> Maybe FilePart -> Response: HTTP response body is sent (by sendfile(), if possible) for GET method. HTTP response body is not sent by HEAD method. Content-Length and Content-Range are automatically added into the HTTP response header if necessary. If Content-Length and Content-Range exist in the HTTP response header, they would cause inconsistency. "Accept-Ranges: bytes" is also inserted.

Applications are categorized into simple and sophisticated. Sophisticated applications should specify Just to Maybe FilePart. They should treat the conditional request by themselves. A proper Status (200 or 206) must be provided.

Simple applications should specify Nothing to Maybe FilePart. The size of the specified file is obtained by disk access or from the file infor cache. If-Modified-Since, If-Unmodified-Since, If-Range and Range are processed. Since a proper status is chosen, Status is ignored. Last-Modified is inserted.

Platform dependent helper functions

setSocketCloseOnExec :: Socket -> IO () Source #

Set flag FileCloseOnExec flag on a socket (on Unix)

Copied from: https://github.com/mzero/plush/blob/master/src/Plush/Server/Warp.hs

Since: 3.2.17

windowsThreadBlockHack :: IO a -> IO a Source #

Misc

http2server :: Settings -> InternalInfo -> Transport -> SockAddr -> Application -> Server Source #

Converting WAI application to the server type of http2 library.

Since 3.3.11

withII :: Settings -> (InternalInfo -> IO a) -> IO a Source #

Running an action with internal info.

Since 3.3.11

pReadMaker :: InternalInfo -> PositionReadMaker Source #

PositionReadMaker based on file descriptor cache.

Since 3.3.13