最近我尝试创建一个iOS应用程序，能够编码和解码Base64，以及其他“语言”，例如十六进制和二进制。我正在尝试创建一个自动解码器（能够自动检测“语言”）。然而，当我碰到Base64时，自动解码器似乎无法检测到有效的Base64，因为Base64字符串中有换行符。我的Base64检测代码如下：
-(BOOL)isBase64Data:(NSString *)input
{
if ([input length] % 4 == 0) {
static NSCharacterSet *invertedBase64CharacterSet = nil;
if (invertedBase64CharacterSet == nil) {
invertedBase64CharacterSet = [[NSCharacterSet characterSetWithCharactersInString:@"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="]invertedSet];
}
return [input rangeOfCharacterFromSet:invertedBase64CharacterSet options:NSLiteralSearch].location == NSNotFound;
}
return NO;
}
仅提供额外信息，以下是我检测NSString中“语言”类型的方法。
-(NSInteger)detectType:(BOOL)base64 hexadecimal:(BOOL)hex binary:(BOOL)binary
{
//Make sure the checking of characters are in this order!
if (binary) {
return 0; //Type 0 means binary
}
else if (hex) {
return 1; //Type 1 means hexadecimal
}
else if (base64) {
return 2; //Type 2 means base64
}
else {
return 3; //Type 3 is error/invalid text
}
}
每当我想要解码时，我只需调用此方法：
-(IBAction)decode:(id)sender
{
//This is where I detect the type
NSInteger type = [self detectType:[self isBase64Data:userInput.text] hexadecimal:[self isHexadecimal:userInput.text] binary:[self isBinary:userInput.text]];
if ([userInput text].length<1) { //First, check if the text view is empty in the first place
WCAlertView *alert=[[WCAlertView alloc]initWithTitle:@"Error: No input!" message:nil delegate:nil cancelButtonTitle:@"Okay" otherButtonTitles:nil, nil];
[alert show];
}
else if (type==0) {
//Initiate the binary converter here
TextBinViewController *binVC=[[TextBinViewController alloc]init];
output.text=[binVC binToText:userInput.text];
}
else if (type==1) {
//Initiate the hexadecimal converter here
TextHexViewController *hexVC=[[TextHexViewController alloc]init];
output.text=[hexVC hexToText:userInput.text];
}
else if (type==2) {
//Initiate the base64 converter here
TextBase64ViewController *baseVC=[[TextBase64ViewController alloc]init];
output.text=[baseVC base64Decode:userInput.text];
}
else {
//If the type matches none of the above, show an error (WCAlertView is a subclass of alertview that allows more styling)
WCAlertView *alert=[[WCAlertView alloc]initWithTitle:@"Error: Invalid input!" message:nil delegate:nil cancelButtonTitle:@"Okay" otherButtonTitles:nil, nil];
[alert show];
output.text=@"";
}
[userInput resignFirstResponder];
}