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"];
}