Reading InputStream into Data

Data.swift

extension Data {
    /**
     Consumes the specified input stream, creating a new Data object
     with its content.
     - Parameter reading: The input stream to read data from.
     - Note: Closes the specified stream.
     */
    init(reading input: InputStream) {
        self.init()
        input.open()
        
        let bufferSize = 1024
        let buffer = UnsafeMutablePointer<UInt8>.allocate(capacity: bufferSize)
        while input.hasBytesAvailable {
            let read = input.read(buffer, maxLength: bufferSize)
            self.append(buffer, count: read)
        }
        buffer.deallocate()
        
        input.close()
    }
    
    /**
        Consumes the specified input stream for up to `byteCount` bytes,
        creating a new Data object with its content.

        - Parameter reading: The input stream to read data from.
        - Parameter byteCount: The maximum number of bytes to read from `reading`.
        - Note: Does _not_ close the specified stream.
    */
    init(reading input: InputStream, for byteCount: Int) {
        self.init()
        input.open()

        let buffer = UnsafeMutablePointer<UInt8>.allocate(capacity: byteCount)
        let read = input.read(buffer, maxLength: byteCount)
        self.append(buffer, count: read)
        buffer.deallocate()
    }
}

DataTest.swift

import Foundation
import XCTest

class DataTests: XCTestCase {
    func testInitFromStream() {
        // Tests some random values, plus the empty case
        [[UInt8](),
         [0b00001001],
         [0b01000000, 0b01001011],
         [0b01011110, 0b11101111, 0b00011001],
         [0b01101100, 0b00101010, 0b10111001, 0b10000111],
         [0b00011011, 0b00010111, 0b00011000, 0b01100100, 0b10110000],
         [UInt8](repeating: 77, count: 2049) // something large; 2*buffersize + 1
            ].forEach { (bytes) in
                let referenceData = Data(bytes)
                let stream = InputStream(data: referenceData)
                XCTAssertEqual(Data(reading: stream), referenceData)
        }
    }
    
    func testInitFromStreamWithMaxLength() {
        // Tests some random values, plus the empty case
        [[UInt8](),
         [0b00001001],
         [0b01000000, 0b01001011],
         [0b01011110, 0b11101111, 0b00011001],
         [0b01101100, 0b00101010, 0b10111001, 0b10000111]
        ].forEach { (bytes) in
            let referenceData = Data(bytes)
            let stream = InputStream(data: referenceData)
            defer { stream.close() }
            XCTAssertEqual(
                    Data(reading: stream, for: 3),
                    referenceData[0..<(min(3, referenceData.count))]
            )
        }
    }
}

Sorry, I completely missed your comment! Do we not get notifications here?

Did you solve the issue? I'm not sure I understand fully what the problem is; I'd recommend you open a question on Stack Overflow!

That said, I don't think the function I've written is suitable for reading from streams that are "slow". At least I never tried it on such.