ASCII ：（American Standard Code for Information Interchange，美國標(biāo)準(zhǔn)信息交換代碼）
Unicode：Unicode 是為了解決傳統(tǒng)的字符編碼方案的局限而產(chǎn)生的，它為每種語言中的每個字符設(shè)定了統(tǒng)一并且唯一的二進(jìn)制編碼，以滿足跨語言、跨平臺進(jìn)行文本轉(zhuǎn)換、處理的要求。
UTF-8 （UTF）：是UnicodeTransformationFormat的縮寫，意為Unicode轉(zhuǎn)換格式,是一種中間格式的字符集。
GB2312（GBK）：GB2312 也是ANSI編碼里的一種，對ANSI編碼最初始的ASCII編碼進(jìn)行擴(kuò)充，為了滿足國內(nèi)在計算機(jī)中使用漢字的需要，中國國家標(biāo)準(zhǔn)總局發(fā)布了一系列的漢字字符集國家標(biāo)準(zhǔn)編碼，統(tǒng)稱為GB碼，或國標(biāo)碼。其中最有影響的是于1980年發(fā)布的《信息交換用漢字編碼字符集 基本集》，標(biāo)準(zhǔn)號為GB 2312-1980,因其使用非常普遍，也常被通稱為國標(biāo)碼。GB2312編碼通行于我國內(nèi)地；新加坡等地也采用此編碼。幾乎所有的中文系統(tǒng)和國際化的軟件都支持GB 2312。
Base64：是網(wǎng)絡(luò)上最常見的用于傳輸8Bit字節(jié)代碼的編碼方式之一,可用于在HTTP環(huán)境下傳遞較長的標(biāo)識信息。
常用編碼間轉(zhuǎn)化：
//Unicode轉(zhuǎn)UTF-8
NSString *unicodeStr = self;
NSString *tempStr1 = [unicodeStr stringByReplacingOccurrencesOfString:@"\\u" withString:@"\\U"];
NSString *tempStr2 = [tempStr1 stringByReplacingOccurrencesOfString:@"\"" withString:@"\\\""];
NSString *tempStr3 = [[@"\"" stringByAppendingString:tempStr2] stringByAppendingString:@"\""];
NSData *tempData = [tempStr3 dataUsingEncoding:NSUTF8StringEncoding];
NSString* returnStr = [NSPropertyListSerialization propertyListFromData:tempData
mutabilityOption:NSPropertyListImmutable
format:NULL
errorDescription:NULL];
return [returnStr stringByReplacingOccurrencesOfString:@"\\r\\n" withString:@"\n"];
}
//UTF-8轉(zhuǎn)Unicode
> ``` +(NSString *) utf8ToUnicode:(NSString *)string
{
NSUInteger length = [string length];
NSMutableString *s = [NSMutableString stringWithCapacity:0];
for (int i = 0;i < length; i++)
{
unichar _char = [string characterAtIndex:i];
//判斷是否為英文和數(shù)字
if (_char <= '9' && _char >= '0')
{
[s appendFormat:@"%@",[string substringWithRange:NSMakeRange(i, 1)]];
}
else if(_char >= 'a' && _char <= 'z')
{
[s appendFormat:@"%@",[string substringWithRange:NSMakeRange(i, 1)]];
}
else if(_char >= 'A' && _char <= 'Z')
{
[s appendFormat:@"%@",[string substringWithRange:NSMakeRange(i, 1)]];
}
else
{
[s appendFormat:@"\\u%x",[string characterAtIndex:i]];
}
}
return s;
}
// NSString to ASCII
int asciiCode = [string characterAtIndex:0]; // 65```
// ASCII to NSString
NSString *string = [NSString stringWithFormat:@"%c", asciiCode]; // A```
一些常用的場景轉(zhuǎn)換：
// url encode
CFStringRef sRef = CFURLCreateStringByAddingPercentEscapes(NULL,
(CFStringRef)self,
NULL,
(CFStringRef)@"!*'\"();:@&=+$,/?%#[]% ",
CFStringConvertNSStringEncodingToEncoding(encoding));
NSString *re = [NSString stringWithFormat:@"%@",sRef];
CFRelease(sRef);
return re;
}
> ```
-(NSString *)urlEncodeWithEncodingUTF8{
return [self urlEncodeUsingEncoding:NSUTF8StringEncoding];
}```
// unicode decode
> ```
-(NSString *)unicodeDecodeString{
NSString *unicodeStr = self;
NSString *tempStr1 = [unicodeStr stringByReplacingOccurrencesOfString:@"\\u" withString:@"\\U"];
NSString *tempStr2 = [tempStr1 stringByReplacingOccurrencesOfString:@"\"" withString:@"\\\""];
NSString *tempStr3 = [[@"\"" stringByAppendingString:tempStr2] stringByAppendingString:@"\""];
NSData *tempData = [tempStr3 dataUsingEncoding:NSUTF8StringEncoding];
NSString* returnStr = [NSPropertyListSerialization propertyListFromData:tempData
mutabilityOption:NSPropertyListImmutable
format:NULL
errorDescription:NULL];
return [returnStr stringByReplacingOccurrencesOfString:@"\\r\\n" withString:@"\n"];
}
常用的加密算法
//MD5
-(NSString *) md5 { const char *cStr = [self UTF8String]; unsigned char digest[CC_MD5_DIGEST_LENGTH]; CC_MD5( cStr, (CC_LONG)strlen(cStr), digest ); NSMutableString *output = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
for(int i = 0; i < CC_MD5_DIGEST_LENGTH; i++) [output appendFormat:@"%02x", digest[i]]; return output; }
//sha1
- (NSString*) sha1 { const char *cstr = [self cStringUsingEncoding:NSUTF8StringEncoding]; NSData *data = [NSData dataWithBytes:cstr length:self.length];
uint8_t digest[CC_SHA1_DIGEST_LENGTH];
CC_SHA1(data.bytes, (CC_LONG)data.length, digest);
NSMutableString* output = [NSMutableString stringWithCapacity:CC_SHA1_DIGEST_LENGTH * 2];
for(int i = 0; i < CC_SHA1_DIGEST_LENGTH; i++) [output appendFormat:@"%02x", digest[i]];
return output;
}
//sha1_base64
- (NSString *) sha1_base64 {
const char *cstr = [self cStringUsingEncoding:NSUTF8StringEncoding];
NSData *data = [NSData dataWithBytes:cstr length:self.length];
uint8_t digest[CC_SHA1_DIGEST_LENGTH]; CC_SHA1(data.bytes, (CC_LONG)data.length, digest); NSData * base64 = [[NSData alloc]initWithBytes:digest length:CC_SHA1_DIGEST_LENGTH]; base64 = [GTMBase64 encodeData:base64]; NSString * output = [[NSString alloc] initWithData:base64 encoding:NSUTF8StringEncoding]; return output; }
//md5_base64
- (NSString *) md5_base64 {
const char *cStr = [self UTF8String]; unsigned char digest[CC_MD5_DIGEST_LENGTH]; CC_MD5( cStr, (CC_LONG)strlen(cStr), digest ); NSData * base64 = [[NSData alloc]initWithBytes:digest length:CC_MD5_DIGEST_LENGTH]; base64 = [GTMBase64 encodeData:base64]; NSString * output = [[NSString alloc] initWithData:base64 encoding:NSUTF8StringEncoding]; return output; }
//base64
NSData * data = [self dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
data = [GTMBase64 encodeData:data];
NSString * output = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
return output;
}
