如何将字节数据转换为十六进制字符串再转成32位有符号补码整数？

Here's the complete implementation of the Data extension for converting to a hex string, including the truncated part from your snippet:

extension Data {
    struct HexEncodingOptions: OptionSet {
        let rawValue: Int
        static let upperCase = HexEncodingOptions(rawValue: 1 << 0)
    }
    
    func hexEncodedString(options: HexEncodingOptions = []) -> String {
        let hexDigits = Array((options.contains(.upperCase) ? "0123456789ABCDEF" : "0123456789abcdef").utf16)
        var chars: [unichar] = []
        chars.reserveCapacity(2 * count)
        
        for byte in self {
            chars.append(hexDigits[Int(byte / 16)])
            chars.append(hexDigits[Int(byte % 16)])
        }
        
        return String(utf16CodeUnits: chars, count: chars.count)
    }
}

Usage with Your Data #

For your specific Data instance:

let data = Data(bytes: [206, 66, 49, 62])

// Lowercase hex string (default behavior)
let lowercaseHex = data.hexEncodedString()
print(lowercaseHex) // Output: "ce42313e"

// Uppercase hex string
let uppercaseHex = data.hexEncodedString(options: .upperCase)
print(uppercaseHex) // Output: "CE42313E"

Quick Breakdown #

• The HexEncodingOptions struct gives you control over whether the output uses uppercase or lowercase hex characters.
• For each byte in the Data object, we split it into two 4-bit "nibbles", map each nibble to its corresponding hex digit, and build the final string from these characters.
• Using reserveCapacity upfront optimizes performance by preallocating exactly the space needed for the output string (2 characters per byte).

内容的提问来源于stack exchange，提问作者tp2376