将 NSData 序列化为十六进制字符串的最佳方法
-
19-09-2019 - |
题
我正在寻找一种很好的可可方法来将 NSData 对象序列化为十六进制字符串。这个想法是在将用于通知的 deviceToken 发送到我的服务器之前对其进行序列化。
我有以下实现,但我认为必须有一些更短、更好的方法来做到这一点。
+ (NSString*) serializeDeviceToken:(NSData*) deviceToken
{
NSMutableString *str = [NSMutableString stringWithCapacity:64];
int length = [deviceToken length];
char *bytes = malloc(sizeof(char) * length);
[deviceToken getBytes:bytes length:length];
for (int i = 0; i < length; i++)
{
[str appendFormat:@"%02.2hhX", bytes[i]];
}
free(bytes);
return str;
}
解决方案
这是施加到NSData的,我写的一个类别。它返回表示NSData的一个十六进制的NSString,其中数据可以是任何长度。如果NSData的是空的,则返回一个空字符串。
<强>的NSData + Conversion.h 强>
#import <Foundation/Foundation.h>
@interface NSData (NSData_Conversion)
#pragma mark - String Conversion
- (NSString *)hexadecimalString;
@end
<强>的NSData + Conversion.m 强>
#import "NSData+Conversion.h"
@implementation NSData (NSData_Conversion)
#pragma mark - String Conversion
- (NSString *)hexadecimalString {
/* Returns hexadecimal string of NSData. Empty string if data is empty. */
const unsigned char *dataBuffer = (const unsigned char *)[self bytes];
if (!dataBuffer)
return [NSString string];
NSUInteger dataLength = [self length];
NSMutableString *hexString = [NSMutableString stringWithCapacity:(dataLength * 2)];
for (int i = 0; i < dataLength; ++i)
[hexString appendString:[NSString stringWithFormat:@"%02lx", (unsigned long)dataBuffer[i]]];
return [NSString stringWithString:hexString];
}
@end
用法:
NSData *someData = ...;
NSString *someDataHexadecimalString = [someData hexadecimalString];
这是“可能”不是调用[someData description]
再剥离的空间,更好的<的和>的。剥字符只是感觉太“哈克”。另外,你永远不知道苹果是否会改变的NSData的-description
的格式在未来。
注意:我已经人与我联系有关许可在这个答案的代码。在此,我奉献我的版权在我张贴在这个答案的公共领域的代码。
其他提示
这是一个高度优化的 NS数据类别 生成十六进制字符串的方法。虽然 @Dave Gallagher 的答案对于相对较小的大小来说是足够的,但对于大量数据来说,内存和 CPU 性能会恶化。我在 iPhone 5 上用一个 2MB 的文件对此进行了分析。时间对比为 0.05 秒与 12 秒。这种方法的内存占用可以忽略不计,而另一种方法则将堆增加到 70MB!
- (NSString *) hexString
{
NSUInteger bytesCount = self.length;
if (bytesCount) {
const char *hexChars = "0123456789ABCDEF";
const unsigned char *dataBuffer = self.bytes;
char *chars = malloc(sizeof(char) * (bytesCount * 2 + 1));
if (chars == NULL) {
// malloc returns null if attempting to allocate more memory than the system can provide. Thanks Cœur
[NSException raise:@"NSInternalInconsistencyException" format:@"Failed to allocate more memory" arguments:nil];
return nil;
}
char *s = chars;
for (unsigned i = 0; i < bytesCount; ++i) {
*s++ = hexChars[((*dataBuffer & 0xF0) >> 4)];
*s++ = hexChars[(*dataBuffer & 0x0F)];
dataBuffer++;
}
*s = '\0';
NSString *hexString = [NSString stringWithUTF8String:chars];
free(chars);
return hexString;
}
return @"";
}
使用的NSData的描述属性不应该被认为对编码串HEX可接受的机制。该属性仅仅是为了说明,并且可以随时更改。作为一个说明,前期的iOS,NSData的说明财产甚至没有以十六进制形式返回它的数据。
对不起重弹的解决方案,但取能量以序列化而不小猪回退预期用于比数据序列别的其他的API是很重要的。
@implementation NSData (Hex)
- (NSString*)hexString
{
NSUInteger length = self.length;
unichar* hexChars = (unichar*)malloc(sizeof(unichar) * (length*2));
unsigned char* bytes = (unsigned char*)self.bytes;
for (NSUInteger i = 0; i < length; i++) {
unichar c = bytes[i] / 16;
if (c < 10) {
c += '0';
} else {
c += 'A' - 10;
}
hexChars[i*2] = c;
c = bytes[i] % 16;
if (c < 10) {
c += '0';
} else {
c += 'A' - 10;
}
hexChars[i*2+1] = c;
}
NSString* retVal = [[NSString alloc] initWithCharactersNoCopy:hexChars length:length*2 freeWhenDone:YES];
return [retVal autorelease];
}
@end
功能夫特版本
一个衬里:
let hexString = UnsafeBufferPointer<UInt8>(start: UnsafePointer(data.bytes),
count: data.length).map { String(format: "%02x", $0) }.joinWithSeparator("")
下面是在可重复使用的和自我记录扩展形式:
extension NSData {
func base16EncodedString(uppercase uppercase: Bool = false) -> String {
let buffer = UnsafeBufferPointer<UInt8>(start: UnsafePointer(self.bytes),
count: self.length)
let hexFormat = uppercase ? "X" : "x"
let formatString = "%02\(hexFormat)"
let bytesAsHexStrings = buffer.map {
String(format: formatString, $0)
}
return bytesAsHexStrings.joinWithSeparator("")
}
}
可替换地,使用reduce("", combine: +)
代替joinWithSeparator("")
要由同行看作是一个功能母。
编辑:我改变字符串($ 0,基数:16)到字符串(格式为: “%02X”,$ 0),因为一个位数需要具有填充零
下面是一种更快的方式进行转换:
的BenchMark(平均时间为1024个字节的数据转换重复100次):
戴夫Gallagher的:〜8.070毫秒,点击 NSProgrammer:〜0.077毫秒结果 彼得:〜0.031毫秒结果 这种情况的一个:〜0.017毫秒
@implementation NSData (BytesExtras)
static char _NSData_BytesConversionString_[512] = "000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f303132333435363738393a3b3c3d3e3f404142434445464748494a4b4c4d4e4f505152535455565758595a5b5c5d5e5f606162636465666768696a6b6c6d6e6f707172737475767778797a7b7c7d7e7f808182838485868788898a8b8c8d8e8f909192939495969798999a9b9c9d9e9fa0a1a2a3a4a5a6a7a8a9aaabacadaeafb0b1b2b3b4b5b6b7b8b9babbbcbdbebfc0c1c2c3c4c5c6c7c8c9cacbcccdcecfd0d1d2d3d4d5d6d7d8d9dadbdcdddedfe0e1e2e3e4e5e6e7e8e9eaebecedeeeff0f1f2f3f4f5f6f7f8f9fafbfcfdfeff";
-(NSString*)bytesString
{
UInt16* mapping = (UInt16*)_NSData_BytesConversionString_;
register UInt16 len = self.length;
char* hexChars = (char*)malloc( sizeof(char) * (len*2) );
// --- Coeur's contribution - a safe way to check the allocation
if (hexChars == NULL) {
// we directly raise an exception instead of using NSAssert to make sure assertion is not disabled as this is irrecoverable
[NSException raise:@"NSInternalInconsistencyException" format:@"failed malloc" arguments:nil];
return nil;
}
// ---
register UInt16* dst = ((UInt16*)hexChars) + len-1;
register unsigned char* src = (unsigned char*)self.bytes + len-1;
while (len--) *dst-- = mapping[*src--];
NSString* retVal = [[NSString alloc] initWithBytesNoCopy:hexChars length:self.length*2 encoding:NSASCIIStringEncoding freeWhenDone:YES];
#if (!__has_feature(objc_arc))
return [retVal autorelease];
#else
return retVal;
#endif
}
@end
彼得的答案移植到斯威夫特
func hexString(data:NSData)->String{
if data.length > 0 {
let hexChars = Array("0123456789abcdef".utf8) as [UInt8];
let buf = UnsafeBufferPointer<UInt8>(start: UnsafePointer(data.bytes), count: data.length);
var output = [UInt8](count: data.length*2 + 1, repeatedValue: 0);
var ix:Int = 0;
for b in buf {
let hi = Int((b & 0xf0) >> 4);
let low = Int(b & 0x0f);
output[ix++] = hexChars[ hi];
output[ix++] = hexChars[low];
}
let result = String.fromCString(UnsafePointer(output))!;
return result;
}
return "";
}
<强> swift3 强>
func hexString()->String{
if count > 0 {
let hexChars = Array("0123456789abcdef".utf8) as [UInt8];
return withUnsafeBytes({ (bytes:UnsafePointer<UInt8>) -> String in
let buf = UnsafeBufferPointer<UInt8>(start: bytes, count: self.count);
var output = [UInt8](repeating: 0, count: self.count*2 + 1);
var ix:Int = 0;
for b in buf {
let hi = Int((b & 0xf0) >> 4);
let low = Int(b & 0x0f);
output[ix] = hexChars[ hi];
ix += 1;
output[ix] = hexChars[low];
ix += 1;
}
return String(cString: UnsafePointer(output));
})
}
return "";
}
夫特5
func hexString()->String{
if count > 0 {
let hexChars = Array("0123456789abcdef".utf8) as [UInt8];
return withUnsafeBytes{ bytes->String in
var output = [UInt8](repeating: 0, count: bytes.count*2 + 1);
var ix:Int = 0;
for b in bytes {
let hi = Int((b & 0xf0) >> 4);
let low = Int(b & 0x0f);
output[ix] = hexChars[ hi];
ix += 1;
output[ix] = hexChars[low];
ix += 1;
}
return String(cString: UnsafePointer(output));
}
}
return "";
}
我需要解决这个问题,发现这里的答案是非常有用的,但我担心性能。大多数这些答案涉及复制散装出来的NSData的数据,所以我写了下面做低开销的转换:
@interface NSData (HexString)
@end
@implementation NSData (HexString)
- (NSString *)hexString {
NSMutableString *string = [NSMutableString stringWithCapacity:self.length * 3];
[self enumerateByteRangesUsingBlock:^(const void *bytes, NSRange byteRange, BOOL *stop){
for (NSUInteger offset = 0; offset < byteRange.length; ++offset) {
uint8_t byte = ((const uint8_t *)bytes)[offset];
if (string.length == 0)
[string appendFormat:@"%02X", byte];
else
[string appendFormat:@" %02X", byte];
}
}];
return string;
}
此预分配的字符串整个结果在空间和通过使用enumerateByteRangesUsingBlock避免不断复制NSData的内容进行。将X更改为格式字符串的x将使用小写十六进制数字。如果你不想字节之间的分隔符可以减少声明
if (string.length == 0)
[string appendFormat:@"%02X", byte];
else
[string appendFormat:@" %02X", byte];
下降到只有
[string appendFormat:@"%02X", byte];
我需要一个答案,将变长字符串的工作,所以这里就是我所做的:
+ (NSString *)stringWithHexFromData:(NSData *)data
{
NSString *result = [[data description] stringByReplacingOccurrencesOfString:@" " withString:@""];
result = [result substringWithRange:NSMakeRange(1, [result length] - 2)];
return result;
}
作为扩展为NSString类巨大的。
您可以随时使用[yourString uppercaseString]以利用在数据描述信
一个更好的方式来序列化/反序列化NSData的成的NSString是使用谷歌工具箱为Mac 的Base64编码器/解码器。只要将您的应用项目中的文件GTMBase64.m,GTMBase64.hēGTMDefines.h从包装基金会和做一些像
/**
* Serialize NSData to Base64 encoded NSString
*/
-(void) serialize:(NSData*)data {
self.encodedData = [GTMBase64 stringByEncodingData:data];
}
/**
* Deserialize Base64 NSString to NSData
*/
-(NSData*) deserialize {
return [GTMBase64 decodeString:self.encodedData];
}
下面是使用溶液夫特3
extension Data {
public var hexadecimalString : String {
var str = ""
enumerateBytes { buffer, index, stop in
for byte in buffer {
str.append(String(format:"%02x",byte))
}
}
return str
}
}
extension NSData {
public var hexadecimalString : String {
return (self as Data).hexadecimalString
}
}
@implementation NSData (Extn)
- (NSString *)description
{
NSMutableString *str = [[NSMutableString alloc] init];
const char *bytes = self.bytes;
for (int i = 0; i < [self length]; i++) {
[str appendFormat:@"%02hhX ", bytes[i]];
}
return [str autorelease];
}
@end
Now you can call NSLog(@"hex value: %@", data)
更改%08x
到%08X
获得资本的字符。
<强>夫特+物业。强>
我更喜欢有十六进制表示为属性(同bytes
和description
属性):
extension NSData {
var hexString: String {
let buffer = UnsafeBufferPointer<UInt8>(start: UnsafePointer(self.bytes), count: self.length)
return buffer.map { String(format: "%02x", $0) }.joinWithSeparator("")
}
var heXString: String {
let buffer = UnsafeBufferPointer<UInt8>(start: UnsafePointer(self.bytes), count: self.length)
return buffer.map { String(format: "%02X", $0) }.joinWithSeparator("")
}
}
观从该借回答
[deviceToken description]
您需要删除的空间。
我个人base64
编码deviceToken
,但它的口味的问题。