Xilinx .bit file header parser

XilinxBitHeaderParser.hpp

class HeaderParser {
private:
    uint8_t state;
    //0=header len, 1=header data,
    //2=key, 3=length, 4=value,
    //5=bitstream len, 6=bitstream
    uint32_t len;
    uint8_t n;
    uint8_t key;

protected:
    virtual void parseKey(uint8_t k, char c)  {
      printf("key 0x%x: %c\n", k, c);
    }

public:
    bool done() {
        return (state == 6);
    }

    void reset() {
        state = 0;
        n = 2;
    }

    size_t bitstream_len() {
        if(state == 6) return len;
        else return 0;
    }

    HeaderParser() {
        reset();
    }

    void operator()(char x) {
        switch(state) {
        case 0: { //record header len
            len = (len << 8) | x;
            n--;
            if(n == 0) {
                n = len & 0x0000ffff;
                if(n == 0x0001) state = 2;  //go key-length-value mode
                else state = 1; //go bitstream len
            }
        } break;
        case 1: //consume header data
            n--;
            if(n == 0) {
                n = 2;
                state = 0;
            }
            break;
        case 2:   //parse key
            key = x;
            if(key == 0x65) {
                n = 4;
                state = 5;
            } else {
                n = 2;
                state = 3;
            }
            break;
        case 3: { //record value len
            len = (len << 8) | x;
            n--;
            if(n == 0) {
                n = len & 0x0000ffff;
                state = 4;
            }
        } break;
        case 4: { //consume value
            parseKey(key, x);
            n--;
            if(n == 0) state = 2;
        } break;
        case 5: { //record bitstream len
            len = (len << 8) | x;
            n--;
            if(n == 0) state = 6; //bitstream len acquired
        }
        case 6:
        default:;
        }
    }
};