[英]Swift NSData String Conversion Based on Subset of NSData
我正在使用二进制数据,该数据的中间编码有一个字符串。 我想做的是提取此字符串,以便可以“设置”和“获取”它。 我想出了一种看起来有点时髦的方法(实际上是3种选择)。 我提供了一个游乐场代码,您可以查看。
我想知道是否有比我提出的更好的方法来处理这些数据。 更好意味着更高效或更清晰的代码方式。
要读取数据,请执行以下操作-
NSMutableData
转换为UnsafeMutablePoitner<UInt8>
来制作var rawData
rawData.mutableBytes
创建var ptr : UnsafeMutablePointer<UInt8>
UnsafeMutableBufferPointer<UInt8>
的数组bytes
bytes[19]
bytes[26]
的字节组成的新数组 然后设置变量,我有3种方法,但我认为我会使用的一种方法:1.制作一个8字符串的新字符串2.创建字符串的字符的[UInt8]
数组3.遍历新数组中的每个字节并将bytes
数组中byte的值设置为有问题的值
我假设有某种方法可以直接使用“父”字节数组,而不是使用子数组。 游乐场代码如下。 我正在寻找一种更清洁的方式来执行此操作,也许没有。
谢谢
import Cocoa
//import AppKit
///This is the raw data
var testBytes : [UInt8] = [0x14, 0x00, 0xAB, 0x45, 0x49, 0x1F, 0xEF, 0x15, 0xA8, 0x89, 0x78, 0x0F, 0x09, 0xA9, 0x07, 0xB0, 0x01, 0x20, 0x01, 0x4E, 0x38, 0x32, 0x35, 0x56, 0x20, 0x20, 0x20, 0x00]
///Convert into msgData
var msgData = NSMutableData(bytes: testBytes, length: testBytes.count)
// Store raw data into a byte array for messing with
var rawData: NSMutableData = NSMutableData(data: msgData)
var ptr: UnsafeMutablePointer<UInt8> = UnsafeMutablePointer<UInt8>(rawData.mutableBytes)
var bytes : UnsafeMutableBufferPointer<UInt8> = UnsafeMutableBufferPointer<UInt8>(start: ptr, count: rawData.length)
// Extract Callsign from the data stream
var callsignArray : [UInt8] = [bytes[19], bytes[20], bytes[21], bytes[22], bytes[23], bytes[24], bytes[25], bytes[26]]
var callsignString = NSString(bytes: callsignArray, length: callsignArray.count, encoding: NSUTF8StringEncoding)
let callsignString0 = callsignString!
println(callsignArray)
println("1. -- Initial Callsign [\(callsignString0)]")
//OPTION #1
// Edit Callsgin Array Directly (sketchy)
// And manually copy the bytes back into the base array
callsignArray[0] = 97
callsignArray[1] = 98
callsignArray[2] = 99
callsignArray[3] = 100
println(callsignArray)
// Write the new "bytes" back into the main array - there must be a better way
for (var i = 0; i <= 7; i++) {
bytes[19+i] = callsignArray[i]
}
let callsign1 = NSString(bytes: callsignArray, length: callsignArray.count, encoding: NSUTF8StringEncoding)!
println("2. -- Modification of Bytes [\(callsign1)]")
//Option 3 - Go from String to Bytes
let callsign3 = "AABCDEF "
var buf = [UInt8](callsign3.utf8)
for (var i = 0; i <= 7; i++) {
bytes[19+i] = buf[i]
}
println(rawData)
callsignArray = [bytes[19], bytes[20], bytes[21], bytes[22], bytes[23], bytes[24], bytes[25], bytes[26]]
callsignString = NSString(bytes: callsignArray, length: callsignArray.count, encoding: NSUTF8StringEncoding)
NSMutableData
具有提取和替换子范围的方法:
// Get:
let subData = msgData.subdataWithRange(NSMakeRange(19, 8))
let string = NSString(data: subData, encoding: NSUTF8StringEncoding)
// Set:
let newString = "AABCDEF "
let newData = newString.dataUsingEncoding(NSUTF8StringEncoding)!
msgData.replaceBytesInRange(NSMakeRange(19, 8), withBytes: newData.bytes, length: newData.length)
您也可以直接在[UInt8]
数组上进行操作:
// Get:
let string = testBytes.withUnsafeBufferPointer {
NSString(bytes: UnsafePointer($0.baseAddress + 19), length: 8, encoding: NSUTF8StringEncoding)
}
// Set:
testBytes.replaceRange(19 ... 26, with: Array(newString.utf8))
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