AFNetworking POST 大量中文字符崩溃

AFURLRequestSerialization.m

/**
 Returns a percent-escaped string following RFC 3986 for a query string key or value.
 RFC 3986 states that the following characters are "reserved" characters.
    - General Delimiters: ":", "#", "[", "]", "@", "?", "/"
    - Sub-Delimiters: "!", "$", "&", "'", "(", ")", "*", "+", ",", ";", "="

 In RFC 3986 - Section 3.4, it states that the "?" and "/" characters should not be escaped to allow
 query strings to include a URL. Therefore, all "reserved" characters with the exception of "?" and "/"
 should be percent-escaped in the query string.
    - parameter string: The string to be percent-escaped.
    - returns: The percent-escaped string.
 */
static NSString * AFPercentEscapedStringFromString(NSString *string) {
    static NSString * const kAFCharactersGeneralDelimitersToEncode = @":#[]@"; // does not include "?" or "/" due to RFC 3986 - Section 3.4
    static NSString * const kAFCharactersSubDelimitersToEncode = @"!$&'()*+,;=";

    NSMutableCharacterSet * allowedCharacterSet = [[NSCharacterSet URLQueryAllowedCharacterSet] mutableCopy];
    [allowedCharacterSet removeCharactersInString:[kAFCharactersGeneralDelimitersToEncode stringByAppendingString:kAFCharactersSubDelimitersToEncode]];
    
    //==========================================================================================================
    //
    //  Batching is required for escaping due to an internal bug in iOS 8.1 and 8.2. Encoding more than a few
    //  hundred Chinense characters causes various malloc error crashes. To avoid this issue until iOS 8 is no
    //  longer supported, batching MUST be used for encoding. This introduces roughly a 20% overhead. For more
    //  info, please refer to:
    //
    //      - https://github.com/Alamofire/Alamofire/issues/206
    //
    //==========================================================================================================
    
    NSString *escaped = @"";

    if (([[UIDevice currentDevice].systemVersion floatValue] >= 8.3)) {
        escaped = [string stringByAddingPercentEncodingWithAllowedCharacters:allowedCharacterSet] ? [string stringByAddingPercentEncodingWithAllowedCharacters:allowedCharacterSet] : string;
    } else {
        NSUInteger batchSize = 50;
        NSUInteger endIndex = string.length;
        NSUInteger index = 0;
        
        while (index != endIndex) {
            NSUInteger startIndex = index;
            NSRange range = NSMakeRange(startIndex, batchSize);
            
            NSInteger delta = NSMaxRange(range) - endIndex;
            if (delta > 0) {
                batchSize -= delta;
                range = NSMakeRange(startIndex, batchSize);
            }
            
            NSString *substring = [string substringWithRange:range];
            
            NSString *escapedSubstring = [substring stringByAddingPercentEncodingWithAllowedCharacters:allowedCharacterSet] ? [substring stringByAddingPercentEncodingWithAllowedCharacters:allowedCharacterSet] : substring;
            escaped = [escaped stringByAppendingString:escapedSubstring];
            
            index += batchSize;
        }
    }
    
    return escaped;
}