如何将文件读入Ints数组 [英] How to read file into array of Ints

问题描述

在我的应用程序文档文件夹中，我有一个文件，试图将每个字节读取到UInt8数组中，其中每个元素代表一个字节.我将如何去做呢?该文件恰好叫做Q1.dat.

In my app documents folder I have a file which I am trying to read byte-per-byte into an array of UInt8 where each element represents a byte. How would I go about doing this? The file happens to be called Q1.dat.

这是我失败的尝试:

func readArray() -> [Int]? {
    if let arrayPath: String = createArrayPath() {
        if let arrayFromFile: [Int] = NSArray(contentsOfFile: arrayPath) as? [Int] {
            return arrayFromFile
        }
    }
    return nil
}

func createArrayPath () -> String? {
    if let docsPath: String = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomainMask.UserDomainMask, true).last {
        return ((docsPath as NSString).stringByAppendingPathComponent("Q1") as NSString).stringByAppendingPathExtension("dat")
    }
    return nil
}

推荐答案

尝试如下操作:

let filePath = "/Path/To/Directory/Q1.dat"

var bytes = [UInt8]()

if let data = NSData(contentsOfFile: filePath) {

    var buffer = [UInt8](count: data.length, repeatedValue: 0)
    data.getBytes(&buffer, length: data.length)
    bytes = buffer
}

对不起，我不在可以对其进行测试的地方，但是稍加修改就可以为您提供一个UInt8数组，每个数组代表文件中的一个字节.

I'm sorry, I'm not in a place where I can test it, but with a little tinkering it should give you an array of UInt8s, each of which represents a byte from the file.

而且，如果您真的希望这是Int s而不是UInt8 s的数组，只需map bytes到Int s的数组:

And if you really want this to be an array of Ints instead of UInt8s, just map bytes to an array of Ints:

let intBytes = bytes.map { Int($0) }

...尽管通常来说，目前尚不清楚为什么您要使用除字节集合以外的任何东西，这些字节集合最适合表示为一系列UInt8.

...although generally speaking it is not clear why you want to work with anything other than a collection of bytes, which are most appropriately represented as a series of UInt8s.

如果您确实真的想要1和0，那么将其附加到末尾应该可以做到:

And if you really, really, want the ones and zeros, then tacking this on to the end should do it:

var onesAndZeros = [UInt8]()

bytes.forEach { byte in

    var array = [UInt8](count: 8, repeatedValue: 0)

    let bits = String(byte, radix: 2).characters.flatMap { UInt8(String($0)) }

    array.replaceRange((8-bits.count)..<8, with: bits)
    onesAndZeros.appendContentsOf(array)
}

再次，我选择了UInt8而不是Int，只是因为这样做更有意义，但是可以根据需要进行更改.

Again, I went with UInt8 instead of Int, just because it makes more sense, but change it up as you need.

只需整理一下，您就可以将这两个操作包装在几个函数中，如下所示:

Just to neaten things up, you can wrap the two operations in a couple of functions like this:

func bytesFromFile(filePath: String) -> [UInt8]? {

    guard let data = NSData(contentsOfFile: filePath) else { return nil }

    var buffer = [UInt8](count: data.length, repeatedValue: 0)
    data.getBytes(&buffer, length: data.length)

    return buffer
}

func bitsFromBytes(bytes: [UInt8]) -> [UInt8] {

    var onesAndZeros = [UInt8]()

    bytes.forEach { byte in

        var array = [UInt8](count: 8, repeatedValue: 0)

        let bits = String(byte, radix: 2).characters.flatMap { UInt8(String($0)) }

        array.replaceRange((8-bits.count)..<8, with: bits)
        onesAndZeros.appendContentsOf(array)
    }

    return onesAndZeros
}

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