blocks|key|1080999|text|不是以你做的方式。您需要编写自己的方法来获取每两个字符，将它们解释为一个int，并将它们存储在一个数组中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1081000|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Not in the way you are doing it. You'll need to write your own method to take every two characters, interpret them as an int, and store them in an array.

blocks|key|1081071|text|NSScanner的scanHexInt:和类似方法可能有助于完成您想要的操作，但您可能需要首先将字符串拆分成更小的块，在这种情况下，手动执行转换可能比使用NSScanner更简单。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1081072|entityMap|0|LINK|mutability|MUTABLE|url|http://developer.apple.com/mac/library/documentation/cocoa/Reference/Foundation/Classes/NSScanner_Class/Reference/Reference.html#//apple_ref/doc/uid/20000159-scanHexInt_^0|0|9|A|B|26|9|A|B|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]|$9|Q|A|R|B|C]|$9|S|A|T|B|C]]|D|@$9|U|A|V|1|W]]|E|$]]|$1|F|3|-4|5|6|7|X|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

The <a href="http://developer.apple.com/mac/library/documentation/cocoa/Reference/Foundation/Classes/NSScanner_Class/Reference/Reference.html#//apple_ref/doc/uid/20000159-scanHexInt_" rel="nofollow noreferrer"><code>scanHexInt:</code></a> and similar methods of <code>NSScanner</code> might be helpful in doing what you want, but you'd probably need to break the string up into smaller chunks first, in which case doing the translation manually might be simpler than using <code>NSScanner</code>.

blocks|key|1296024|text|@interface+NSString+(NSStringHexToBytes)
-(NSData*)+hexToBytes+;
@end



@implementation+NSString+(NSStringHexToBytes)
-(NSData*)+hexToBytes+{
++NSMutableData*+data+=+[NSMutableData+data];
++int+idx;
++for+(idx+=+0;+idx%2B2+<=+self.length;+idx%2B=2)+{
++++NSRange+range+=+NSMakeRange(idx,+2);
++++NSString*+hexStr+=+[self+substringWithRange:range];
++++NSScanner*+scanner+=+[NSScanner+scannerWithString:hexStr];
++++unsigned+int+intValue;
++++[scanner+scanHexInt:&intValue];
++++[data+appendBytes:&intValue+length:1];
++}
++return+data;
}
@end



///+example
unsigned+char+bytes[]+=+{+0x11,+0x56,+0xFF,+0xCD,+0x34,+0x30,+0xAA,+0x22+};
NSData*+expectedData+=+[NSData+dataWithBytes:bytes+length:sizeof(bytes)];
NSLog(@"data+%25@",+[@"1156FFCD3430AA22"+hexToBytes]);
NSLog(@"expectedData+isEqual:%25d",+[expectedData+isEqual:[@"1156FFCD3430AA22"+hexToBytes]]);|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1296025|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>@interface NSString (NSStringHexToBytes)
-(NSData*) hexToBytes ;
@end



@implementation NSString (NSStringHexToBytes)
-(NSData*) hexToBytes {
 NSMutableData* data = [NSMutableData data];
 int idx;
 for (idx = 0; idx+2 &lt;= self.length; idx+=2) {
 NSRange range = NSMakeRange(idx, 2);
 NSString* hexStr = [self substringWithRange:range];
 NSScanner* scanner = [NSScanner scannerWithString:hexStr];
 unsigned int intValue;
 [scanner scanHexInt:&amp;intValue];
 [data appendBytes:&amp;intValue length:1];
 }
 return data;
}
@end



/// example
unsigned char bytes[] = { 0x11, 0x56, 0xFF, 0xCD, 0x34, 0x30, 0xAA, 0x22 };
NSData* expectedData = [NSData dataWithBytes:bytes length:sizeof(bytes)];
NSLog(@"data %@", [@"1156FFCD3430AA22" hexToBytes]);
NSLog(@"expectedData isEqual:%d", [expectedData isEqual:[@"1156FFCD3430AA22" hexToBytes]]);
</code></pre>

blocks|key|1296096|text|改进的方法，|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1296097|/*+Converts+a+hex+string+to+bytes.
+Precondition:
+.+The+hex+string+can+be+separated+by+space+or+not.
+.+the+string+length+without+space+or+0x,+must+be+even.+2+symbols+for+one+byte/char
+.+sample+input:+23+3A+F1+OR+233AF1,+0x23+0X231f+2B
+*/

%2B+(NSData+*)+dataFromHexString:(NSString*)hexString
{
++++NSString+*+cleanString+=+[Util+cleanNonHexCharsFromHexString:hexString];
++++if+(cleanString+==+nil)+{
++++++++return+nil;
++++}

++++NSMutableData+*result+=+[[NSMutableData+alloc]+init];

++++int+i+=+0;
++++for+(i+=+0;+i%2B2+<=+cleanString.length;+i%2B=2)+{
++++++++NSRange+range+=+NSMakeRange(i,+2);
++++++++NSString*+hexStr+=+[cleanString+substringWithRange:range];
++++++++NSScanner*+scanner+=+[NSScanner+scannerWithString:hexStr];
++++++++unsigned+int+intValue;
++++++++[scanner+scanHexInt:&intValue];
++++++++unsigned+char+uc+=+(unsigned+char)+intValue;
++++++++[result+appendBytes:&uc+length:1];
++++}
++++NSData+*+data+=+[NSData+dataWithData:result];
++++[result+release];
++++return+data;
}

/*+Clean+a+hex+string+by+removing+spaces+and+0x+chars.
+.+The+hex+string+can+be+separated+by+space+or+not.
+.+sample+input:+23+3A+F1;+233AF1;+0x23+0x3A+0xf1
+*/

%2B+(NSString+*)+cleanNonHexCharsFromHexString:(NSString+*)input
{
++++if+(input+==+nil)+{
++++++++return+nil;
++++}

++++NSString+*+output+=+[input+stringByReplacingOccurrencesOfString:@"0x"+withString:@""
++++++++++++++++++++++++++++++++++++options:NSCaseInsensitiveSearch+range:NSMakeRange(0,+input.length)];
++++NSString+*+hexChars+=+@"0123456789abcdefABCDEF";
++++NSCharacterSet+*hexc+=+[NSCharacterSet+characterSetWithCharactersInString:hexChars];
++++NSCharacterSet+*invalidHexc+=+[hexc+invertedSet];
++++NSString+*+allHex+=+[[output+componentsSeparatedByCharactersInSet:invalidHexc]+componentsJoinedByString:@""];
++++return+allHex;
}|code-block|syntax|javascript|1296098|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Modified approach,

<pre><code>/* Converts a hex string to bytes.
 Precondition:
 . The hex string can be separated by space or not.
 . the string length without space or 0x, must be even. 2 symbols for one byte/char
 . sample input: 23 3A F1 OR 233AF1, 0x23 0X231f 2B
 */

+ (NSData *) dataFromHexString:(NSString*)hexString
{
 NSString * cleanString = [Util cleanNonHexCharsFromHexString:hexString];
 if (cleanString == nil) {
 return nil;
 }

 NSMutableData *result = [[NSMutableData alloc] init];

 int i = 0;
 for (i = 0; i+2 &lt;= cleanString.length; i+=2) {
 NSRange range = NSMakeRange(i, 2);
 NSString* hexStr = [cleanString substringWithRange:range];
 NSScanner* scanner = [NSScanner scannerWithString:hexStr];
 unsigned int intValue;
 [scanner scanHexInt:&amp;intValue];
 unsigned char uc = (unsigned char) intValue;
 [result appendBytes:&amp;uc length:1];
 }
 NSData * data = [NSData dataWithData:result];
 [result release];
 return data;
}

/* Clean a hex string by removing spaces and 0x chars.
 . The hex string can be separated by space or not.
 . sample input: 23 3A F1; 233AF1; 0x23 0x3A 0xf1
 */

+ (NSString *) cleanNonHexCharsFromHexString:(NSString *)input
{
 if (input == nil) {
 return nil;
 }

 NSString * output = [input stringByReplacingOccurrencesOfString:@"0x" withString:@""
 options:NSCaseInsensitiveSearch range:NSMakeRange(0, input.length)];
 NSString * hexChars = @"0123456789abcdefABCDEF";
 NSCharacterSet *hexc = [NSCharacterSet characterSetWithCharactersInString:hexChars];
 NSCharacterSet *invalidHexc = [hexc invertedSet];
 NSString * allHex = [[output componentsSeparatedByCharactersInSet:invalidHexc] componentsJoinedByString:@""];
 return allHex;
}
</code></pre>

blocks|key|1081165|text|我能想到的最快的NSString类别实现(一些例子的鸡尾酒)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1081166|-+(NSData+*)dataFromHexString+{
++++const+char+*chars+=+[self+UTF8String];
++++int+i+=+0,+len+=+self.length;

++++NSMutableData+*data+=+[NSMutableData+dataWithCapacity:len+/+2];
++++char+byteChars[3]+=+{'\0','\0','\0'};
++++unsigned+long+wholeByte;

++++while+(i+<+len)+{
++++++++byteChars[0]+=+chars[i%2B%2B];
++++++++byteChars[1]+=+chars[i%2B%2B];
++++++++wholeByte+=+strtoul(byteChars,+NULL,+16);
++++++++[data+appendBytes:&wholeByte+length:1];
++++}

++++return+data;
}|code-block|syntax|javascript|1081167|它比wookay的解决方案快近8倍。NSScanner相当慢。|1081168|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Fastest NSString category implementation that I could think of (cocktail of some examples):

<pre><code>- (NSData *)dataFromHexString {
 const char *chars = [self UTF8String];
 int i = 0, len = self.length;

 NSMutableData *data = [NSMutableData dataWithCapacity:len / 2];
 char byteChars[3] = {'\0','\0','\0'};
 unsigned long wholeByte;

 while (i &lt; len) {
 byteChars[0] = chars[i++];
 byteChars[1] = chars[i++];
 wholeByte = strtoul(byteChars, NULL, 16);
 [data appendBytes:&amp;wholeByte length:1];
 }

 return data;
}
</code></pre>

It is close to 8 times faster than wookay's solution. NSScanner is quite slow.

blocks|key|1296177|text|Swift+2.2中的第一次尝试：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1296178|func+hexStringToBytes(hexString:+String)+->+NSData?+{
++++guard+let+chars+=+hexString.cStringUsingEncoding(NSUTF8StringEncoding)+else+{+return+nil}
++++var+i+=+0
++++let+length+=+hexString.characters.count

++++let+data+=+NSMutableData(capacity:+length/2)
++++var+byteChars:+[CChar]+=+[0,+0,+0]

++++var+wholeByte:+CUnsignedLong+=+0

++++while+i+<+length+{
++++++++byteChars[0]+=+chars[i]
++++++++i%2B=1
++++++++byteChars[1]+=+chars[i]
++++++++i%2B=1
++++++++wholeByte+=+strtoul(byteChars,+nil,+16)
++++++++data?.appendBytes(&wholeByte,+length:+1)
++++}

++++return+data
}|code-block|syntax|javascript|1296179|或者，作为字符串的扩展：|1296180|extension+String+{

++++func+dataFromHexString()+->+NSData?+{
++++++++guard+let+chars+=+cStringUsingEncoding(NSUTF8StringEncoding)+else+{+return+nil}
++++++++var+i+=+0
++++++++let+length+=+characters.count

++++++++let+data+=+NSMutableData(capacity:+length/2)
++++++++var+byteChars:+[CChar]+=+[0,+0,+0]

++++++++var+wholeByte:+CUnsignedLong+=+0

++++++++while+i+<+length+{
++++++++++++byteChars[0]+=+chars[i]
++++++++++++i%2B=1
++++++++++++byteChars[1]+=+chars[i]
++++++++++++i%2B=1
++++++++++++wholeByte+=+strtoul(byteChars,+nil,+16)
++++++++++++data?.appendBytes(&wholeByte,+length:+1)
++++++++}

++++++++return+data
++++}
}|1296181|这是一个持续进行中的工作，但到目前为止似乎工作得很好。|1296182|可以在Code+Review上找到进一步的优化和更深入的讨论。|offset|length|1296183|entityMap|0|LINK|mutability|MUTABLE|url|https://codereview.stackexchange.com/q/135424/73433^0|0|0|0|0|0|3|B|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|10|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|12|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|13|8|@]|9|@$O|14|P|15|1|16]]|A|$]]|$1|Q|3|-4|5|6|7|17|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|X]]]]

First attempt in Swift 2.2:

<pre><code>func hexStringToBytes(hexString: String) -&gt; NSData? {
 guard let chars = hexString.cStringUsingEncoding(NSUTF8StringEncoding) else { return nil}
 var i = 0
 let length = hexString.characters.count

 let data = NSMutableData(capacity: length/2)
 var byteChars: [CChar] = [0, 0, 0]

 var wholeByte: CUnsignedLong = 0

 while i &lt; length {
 byteChars[0] = chars[i]
 i+=1
 byteChars[1] = chars[i]
 i+=1
 wholeByte = strtoul(byteChars, nil, 16)
 data?.appendBytes(&amp;wholeByte, length: 1)
 }

 return data
}
</code></pre>

Or, as an extension on String:

<pre><code>extension String {

 func dataFromHexString() -&gt; NSData? {
 guard let chars = cStringUsingEncoding(NSUTF8StringEncoding) else { return nil}
 var i = 0
 let length = characters.count

 let data = NSMutableData(capacity: length/2)
 var byteChars: [CChar] = [0, 0, 0]

 var wholeByte: CUnsignedLong = 0

 while i &lt; length {
 byteChars[0] = chars[i]
 i+=1
 byteChars[1] = chars[i]
 i+=1
 wholeByte = strtoul(byteChars, nil, 16)
 data?.appendBytes(&amp;wholeByte, length: 1)
 }

 return data
 }
}
</code></pre>

This is a continuous work-in-progress, but appears to work well so far.

Further optimizations and a more in-depth discussion can be found on <a href="https://codereview.stackexchange.com/q/135424/73433">Code Review</a>.

Is there any method in Objective-C that converts a hex string to bytes? For example <code>@"1156FFCD3430AA22"</code> to an <code>unsigned char array {0x11, 0x56, 0xFF, ...}</code>.

NSString (hex) to bytes

Objective-C

Swift

Objective-C中是否有将十六进制字符串转换为字节的方法？例如，连接到unsigned char array {0x11, 0x56, 0xFF, ...}的@"1156FFCD3430AA22"。

问NSString (十六进制)到字节
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