After searching for a while, I can't figure out how to get this simple result:
let byte : UInt8 = 0xF3 //Should become "F3"
I have tried this method that won't compile when passing-in either a byte or a byte array.
Two ways:
let s1 = String(byte, radix: 16, uppercase: true) // does not do 0-padding but works with
// all radices between 2 and 36
let s2 = String(format: "%02X", byte) // very similar to C
Related
I need to do bitwise OR of two binary strings.
For example, if the binary strings are "110001" and "101101", then I need the result as "111101".
How can I do this in Swift ?
You can convert it first into Int
let a = Int("110001", radix: 2)!
let b = Int("101101", radix: 2)!
let c = a | b
let stringResult = String(c, radix: 2, uppercase: false)
More info:
Int init(_:radix:)
String init(_:radix:uppercase:)
I'm using a C function in my Swift code which produces the following result (when called in Swift):
let result: UInt64 = 586512487604551679
When I call the function in C, I get:
8229a7fffffffff
However, when I convert the Swift result to hexadecimal, I get a different value.
let hex = String(result, radix: 16, uppercase: false)
print(hex) // 823b5ffffffffff
When I print from C, I use the following print statement:
printf("The index is: %" PRIx64 "\n", indexed);
What is the PRIx64 format and is that what's causing the discrepancy? In C, the value is of type uint64_t.
I've no idea what PRIx64 is. I did this:
uint64_t t = 586512487604551679;
NSString* s = [NSString stringWithFormat:#"%llx", t];
NSLog(#"%#", s); // 823b5ffffffffff
and
let t : UInt64 = 586512487604551679
let s = String(t, radix:16)
print(s) // 823b5ffffffffff
I have an array of UInt8 and I want to calculate CheckSum8 Modulo 256.
If sum of bytes is less than 255, checkSum function returns correct value.
e.g
let bytes1 : [UInt8] = [1, 0xa1]
let validCheck = checkSum(data : bytes1) // 162 = 0xa2
let bytes : [UInt8] = [6, 0xB1, 27,0xc5,0xf5,0x9d]
let invalidCheck = checkSum(data : bytes) // 41
Below function returns 41 but expected checksum is 35.
func checkSum(data: [UInt8]) -> UInt8 {
var sum = 0
for i in 0..<data.count {
sum += Int(data[i])
}
let retVal = sum & 0xff
return UInt8(retVal)
}
Your checkSum method is largely right. If you want, you could simplify it to:
func checkSum(_ values: [UInt8]) -> UInt8 {
let result = values.reduce(0) { ($0 + UInt32($1)) & 0xff }
return UInt8(result)
}
You point out a web site that reports the checksum8 for 06B127c5f59d is 35.
The problem is that in your array has 27, not 0x27. If you have hexadecimal values, you always need the 0x prefix for each value in your array literal (or, technically, at least if the value is larger than 9).
So, consider:
let values: [UInt8] = [0x06, 0xB1, 0x27, 0xc5, 0xf5, 0x9d]
let result = checkSum(values)
That’s 53. If you want to see that in hexadecimal (like that site you referred to):
let hex = String(result, radix: 16)
That shows us that the checksum is 0x35 in hexadecimal.
In my project, I communicate with a bluetooth device, the bluetooth device must send me a timestamp second, I received in byte:
[2,6,239]
When I convert converted to a string:
let payloadString = payload.map {
String(format: "%02x", $0)
}
Output:
["02", "06","ef"]
When I converted from the website 0206ef = 132847 seconds
How can I directly convert my aray [2,6,239] in second (= 132847 seconds)?
And if it's complicated then translate my array ["02", "06,"ef"] in second (= 132847 seconds)
The payload contains the bytes of the binary representation of the value.
You convert it back to the value by shifting each byte into its corresponding position:
let payload: [UInt8] = [2, 6, 239]
let value = Int(payload[0]) << 16 + Int(payload[1]) << 8 + Int(payload[2])
print(value) // 132847
The important point is to convert the bytes to integers before shifting, otherwise an overflow error would occur. Alternatively,
with multiplication:
let value = (Int(payload[0]) * 256 + Int(payload[1])) * 256 + Int(payload[2])
or
let value = payload.reduce(0) { $0 * 256 + Int($1) }
The last approach works with an arbitrary number of bytes – as long as
the result fits into an Int. For 4...8 bytes you better choose UInt64
to avoid overflow errors:
let value = payload.reduce(0) { $0 * 256 + UInt64($1) }
payloadString string can be reduced to hexStr and then converted to decimal
var payload = [2,6,239];
let payloadString = payload.map {
String(format: "%02x", $0)
}
//let hexStr = payloadString.reduce(""){$0 + $1}
let hexStr = payloadString.joined()
if let value = UInt64(hexStr, radix: 16) {
print(value)//132847
}
Hy everyone,
I need to transform a Int to its hexadecimal value.
Example : -40 => D8
I have a working method for positive (or unsigned) Int but it doesn't work as expected with negatives. Here's my code.
class func encodeHex(data:[Int]) -> String {
let hexadecimal = data.reduce("") { (string , element) in
var append = String(element, radix:16 , uppercase : false)
if append.characters.count == 1 {
append = "0" + append
}
return string + append
}
return hexadecimal
}
If I pass -40 I get -28.
Can anyone help ? Thanks :)
I assume from your existing code that all integers are in the range
-128 ... 127. Then this would work:
func encodeHex(data:[Int]) -> String {
return data.map { String(format: "%02hhX", $0) }.joined()
}
The "%02hhX" format prints the least significant byte of the
given integer in base 16 with 2 digits.
Example:
print(encodeHex(data: [40, -40, 127, -128]))
// 28D87F80
D8 is the last byte of binary representation of -40. The remaining three bytes are all FFs.
If you are looking for a string that represents only the last byte, you can obtain by first converting your number to unsigned 8-bit integer, and then converting it to hex, like this:
let x = UInt8(bitPattern:Int8(data))
let res = String(format:"%02X", x)