Swift将Int16和Int32 var串联为一个多字节实体

Question

I am writing code to read and write file using a rigidly defined binary format. I have a mixture of Int16 and Int32 values, which are defined as a 240 byte structure. How do I concatenate these values into this single structure?

Answer 1

here is an example, you can custom your own init method, use loop if there two many repeated length

public struct HistoryRecord {
    public let sequence: UInt8
    let impFlag: UInt8
    let mode: UInt8
    let power: UInt16
    let utc: UInt32
    let weight: UInt16
    let impedance: UInt16

    private let sequenceLength = 1
    private let modeLength = 1
    private let powerLength = 2
    private let utcLength = 4
    private let weightLength = 2
    private let impedanceLength = 2

    public init() {
        sequence = 0
        impFlag = 0
        mode = 0
        power = 0
        utc = 0
        weight = 0
        impedance = 0
    }

    public init?(_ data: NSData) {
        let needLength = sequenceLength + modeLength + powerLength + utcLength + weightLength + impedanceLength
        guard data.length == needLength else {
            return nil
        }
        var bufferUInt8: UInt8
        var bufferUInt16: UInt16
        var bufferUInt32: UInt32

        bufferUInt8 = 0
        data.getBytes(&bufferUInt8, range: NSMakeRange(0, sequenceLength))
        sequence = bufferUInt8

        bufferUInt8 = 0
        data.getBytes(&bufferUInt8, range: NSMakeRange(sequenceLength, modeLength))
        impFlag = (bufferUInt8 >> 4) & 0x00ff
        mode = bufferUInt8 & 0x00ff


        bufferUInt16 = 0
        data.getBytes(&bufferUInt16, range: NSMakeRange(sequenceLength + modeLength, powerLength))
        power = bufferUInt16.bigEndian

        bufferUInt32 = 0
        data.getBytes(&bufferUInt32, range: NSMakeRange(sequenceLength + modeLength + powerLength, utcLength))
        utc = bufferUInt32.bigEndian

        bufferUInt16 = 0
        data.getBytes(&bufferUInt16, range: NSMakeRange(sequenceLength + modeLength + powerLength + utcLength, weightLength))
        weight = bufferUInt16.bigEndian

        bufferUInt16 = 0
        data.getBytes(&bufferUInt16, range: NSMakeRange(sequenceLength + modeLength + powerLength + utcLength + weightLength, impedanceLength))
        impedance = bufferUInt16.bigEndian