How to fix Buffer Size Literal Overflow issue in an iOS project?

Question

In NSData+Base64.m, there is a risk of buffer overflow. I tried to add memset() to fix it. I also found another way to fix it by migrating the entire project to ARC. However, it may not be my first choice, because it might cause more unpredictable issues. Does anyone have any suggestions about this issue?

Following code is fixed with memset() added, and I don't know if it works:

- (id) initWithBase64EncodedString:(NSString *) string {
    NSMutableData *mutableData = nil;
    
    if( string ) {
        unsigned long ixtext = 0;
        unsigned long lentext = 0;
        unsigned char ch = 0;
        unsigned char inbuf[3], outbuf[4];
        short i = 0, ixinbuf = 0;
        BOOL flignore = NO;
        BOOL flendtext = NO;
        NSData *base64Data = nil;
        const unsigned char *base64Bytes = nil;
        
        // memset() added here
        memset((void *) inbuf, 0x0, (size_t) sizeof(inbuf));
        
        // Convert the string to ASCII data.
        base64Data = [string dataUsingEncoding:NSASCIIStringEncoding];
        base64Bytes = [base64Data bytes];
        mutableData = [NSMutableData dataWithCapacity:[base64Data length]];
        lentext = [base64Data length];
        
        while( YES ) {
            if( ixtext >= lentext ) break;
            ch = base64Bytes[ixtext++];
            flignore = NO;
            
            if( ( ch >= 'A' ) && ( ch <= 'Z' ) ) ch = ch - 'A';
            else if( ( ch >= 'a' ) && ( ch <= 'z' ) ) ch = ch - 'a' + 26;
            else if( ( ch >= '0' ) && ( ch <= '9' ) ) ch = ch - '0' + 52;
            else if( ch == '+' ) ch = 62;
            else if( ch == '=' ) flendtext = YES;
            else if( ch == '/' ) ch = 63;
            else flignore = YES; 
            
            if( ! flignore ) {
                short ctcharsinbuf = 3;
                BOOL flbreak = NO;
                
                if( flendtext ) {
                    if( ! ixinbuf ) break;
                    if( ( ixinbuf == 1 ) || ( ixinbuf == 2 ) ) ctcharsinbuf = 1;
                    else ctcharsinbuf = 2;
                    ixinbuf = 3;
                    flbreak = YES;
                }
                
                inbuf [ixinbuf++] = ch;
                
                if( ixinbuf == 4 ) {
                    ixinbuf = 0;
                    outbuf [0] = ( inbuf[0] << 2 ) | ( ( inbuf[1] & 0x30) >> 4 );
                    outbuf [1] = ( ( inbuf[1] & 0x0F ) << 4 ) | ( ( inbuf[2] & 0x3C ) >> 2 );
                    outbuf [2] = ( ( inbuf[2] & 0x03 ) << 6 ) | ( inbuf[3] & 0x3F )  ;
                    
                    for( i = 0; i < ctcharsinbuf; i++ ) 
                        [mutableData appendBytes:&outbuf[i] length:1];
                }
                
                if( flbreak )  break;
            }
        }
    }
    
    self = [self initWithData:mutableData];
    return self;
}