Hi swift-corelibs-dev,
Similar to my question "driving writev(2) from DispatchData" [1] (much
appreciated if someone had an answer for that), today I'd like to know if
there's a better way to drive writev(2) [2] from a list of Data.
Sure, I can get the pointers to the individual Data using
someData.withUnsafeBytes {} but that only gives me one pointer, for writev,
I'll need them all to call writev. The only way without violating the contract
of withUnsafeBytes {} I could come up with is using recursion which is
obviously not great :\.
Here my untested demo implementation using recursion to show what I mean:
--- SNIP ---
func dataListWriteV(fileDescriptor: Int32, datas: [Data]) -> Int {
let maxRecursionDepth = 32
var datas = datas
var allPointers: [UnsafeBufferPointer<UInt8>] = []
func dataListWriteV_(datas: inout [Data], myIndex: Int) -> Int {
let myData: Data = datas[myIndex]
return myData.withUnsafeBytes { (myPtr: UnsafePointer<UInt8>) -> Int in
allPointers.append(UnsafeBufferPointer(start: myPtr, count:
myData.count))
if myIndex + 1 >= datas.count || myIndex > maxRecursionDepth {
var iovecs = allPointers.map { iovec(iov_base:
UnsafeMutableRawPointer(mutating: $0.baseAddress),
iov_len: $0.count) }
return writev(fileDescriptor, &iovecs, Int32(iovecs.count))
} else {
return dataListWriteV_(datas: &datas, myIndex: myIndex+1)
}
}
}
return dataListWriteV_(datas: &datas, myIndex: 0)
}
--- SNAP ---
[1]: https://www.mail-archive.com/swift-corelibs-dev@swift.org/msg00930.html
[2]: https://linux.die.net/man/2/writev
--
Johannes
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