iOS开发之MD5封装及应用

一、MD5的封装

 #define CC_MD5_DIGEST_LENGTH    16    

 - (NSString *)toMD5
 {
     const char* input = [self UTF8String];
     unsigned char result[CC_MD5_DIGEST_LENGTH];
     CC_MD5(input, (CC_LONG)strlen(input), result);

     NSMutableString *digest = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * ];
     ; i < CC_MD5_DIGEST_LENGTH; i++) {
         [digest appendFormat:@"%02x", result[i]];
     }

     return digest;
 }

二、生成独一无二的图片名称

　　1）根据URLString来生成

 - (NSString*) genImageName:(NSString *)urlString
 {
     NSString *imageName = [urlString toMD5];
     return [imageName stringByAppendingPathExtension:@"png"];
 }

　　2） 根据时间戳来生成(绝对独一无二)

 +(NSString *)createCUID
 {
     NSString *prefix = [NSString stringWithFormat:@"%ld", (long)[[NSDate date] timeIntervalSince1970]];
     NSString *  result;
     CFUUIDRef   uuid;
     CFStringRef uuidStr;
     uuid = CFUUIDCreate(NULL);
     uuidStr = CFUUIDCreateString(NULL, uuid);
     result =[NSString stringWithFormat:@"%@-%@",prefix,uuidStr];
     CFRelease(uuidStr);
     CFRelease(uuid);
     return [result toMD5];
 }

 //生成图片名，统一用png
 static inline NSString* genImageName()
 {
     NSString *imageName = [NSString createCUID];
     return [imageName stringByAppendingPathExtension:@"png"];
 }