iOS开发之MD5封装及应用

一、MD5的封装

 1 #define CC_MD5_DIGEST_LENGTH    16
 2
 3 - (NSString *)toMD5
 4 {
 5     const char* input = [self UTF8String];
 6     unsigned char result[CC_MD5_DIGEST_LENGTH];
 7     CC_MD5(input, (CC_LONG)strlen(input), result);
 8
 9     NSMutableString *digest = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
10     for (NSInteger i = 0; i < CC_MD5_DIGEST_LENGTH; i++) {
11         [digest appendFormat:@"%02x", result[i]];
12     }
13
14     return digest;
15 }

二、生成独一无二的图片名称

　　1）根据URLString来生成

1 - (NSString*) genImageName:(NSString *)urlString
2 {
3     NSString *imageName = [urlString toMD5];
4     return [imageName stringByAppendingPathExtension:@"png"];
5 }

　　2） 根据时间戳来生成(绝对独一无二)

 1 +(NSString *)createCUID
 2 {
 3     NSString *prefix = [NSString stringWithFormat:@"%ld", (long)[[NSDate date] timeIntervalSince1970]];
 4     NSString *  result;
 5     CFUUIDRef   uuid;
 6     CFStringRef uuidStr;
 7     uuid = CFUUIDCreate(NULL);
 8     uuidStr = CFUUIDCreateString(NULL, uuid);
 9     result =[NSString stringWithFormat:@"%@-%@",prefix,uuidStr];
10     CFRelease(uuidStr);
11     CFRelease(uuid);
12     return [result toMD5];
13 }
14
15 //生成图片名，统一用png
16 static inline NSString* genImageName()
17 {
18     NSString *imageName = [NSString createCUID];
19     return [imageName stringByAppendingPathExtension:@"png"];
20 }