m3u8使用c++ stl解析

写了一个简单的m3u8解析的方法，把m3u8读取到string，然后输出一个vector：

struct M3u8TS
{
    string ts_url;
    double duration;
    
    bool operator< (M3u8TS b)const{
        return ts_url < b.ts_url;
    }
};

class String
{
private:
    string value;
public:
    String(string str = ""){
        value = str;
    }
public:
    String& set_str(string str){
        value = str;
        return *this;
    }
    int length(){
        return (int)value.length();
    }
    bool startswith(string key, String* left = NULL){
        size_t pos = value.find(key);
        
        if(pos == 0 && left != NULL){
            left->set_str(value.substr(pos + key.length()));
            left->strip();
        }
        
        return pos == 0;
    }
    bool endswith(string key, String* left = NULL){
        size_t pos = value.rfind(key);
        
        if(pos == value.length() - key.length() && left != NULL){
            left->set_str(value.substr(pos));
            left->strip();
        }
        
        return pos == value.length() - key.length();
    }
    String& strip(){
        while(value.length() > 0){
            if(startswith("\n")){
                value = value.substr(1);
                continue;
            }
            
            if(startswith("\r")){
                value = value.substr(1);
                continue;
            }
            
            if(startswith(" ")){
                value = value.substr(1);
                continue;
            }
            
            if(endswith("\n")){
                value = value.substr(0, value.length() - 1);
                continue;
            }
            
            if(endswith("\r")){
                value = value.substr(0, value.length() - 1);
                continue;
            }
            
            if(endswith(" ")){
                value = value.substr(0, value.length() - 1);
                continue;
            }

            break;
        }
        
        return *this;
    }
    string getline(){
        size_t pos = string::npos;
        
        if((pos = value.find("\n")) != string::npos){
            return value.substr(0, pos);
        }
        
        return value;
    }
    String& remove(int size){
        if(size >= (int)value.length()){
            value = "";
            return *this;
        }
        
        value = value.substr(size);
        return *this;
    }
    const char* c_str(){
        return value.c_str();
    }
};

int StHlsTask::ParseM3u8Data(string m3u8, vector& ts_objects){
    int ret = ERROR_SUCCESS;
    
    String data(m3u8);
    
    // http://tools.ietf.org/html/draft-pantos-http-live-streaming-08#section-3.3.1
    // An Extended M3U file is distinguished from a basic M3U file by its
    // first line, which MUST be the tag #EXTM3U.
    if(!data.startswith("#EXTM3U")){
        ret = ERROR_HLS_INVALID;
        Error("invalid hls, #EXTM3U not found. ret=%d", ret);
        return ret;
    }
    
    String value;
    int target_duration = 0;
    
    
    M3u8TS ts_object;
    while(data.length() > 0){
        String line;
        data.remove(line.set_str(data.strip().getline()).strip().length()).strip();

        // http://tools.ietf.org/html/draft-pantos-http-live-streaming-08#section-3.4.2
        // #EXT-X-TARGETDURATION:
        // where s is an integer indicating the target duration in seconds.
        if(line.startswith("#EXT-X-TARGETDURATION:", &value)){
            target_duration = atoi(value.c_str());
            ts_object.duration = target_duration;
            continue;
        }
        
        // http://tools.ietf.org/html/draft-pantos-http-live-streaming-08#section-3.3.2
        // #EXTINF:,