bitreader_helper.h

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namespace bitreader_helper {

    inline static size_t extract_bit(const t_uint8 * p_stream,size_t p_offset) {
        return (p_stream[p_offset>>3] >> (7-(p_offset&7)))&1;
    }

    inline static size_t extract_int(const t_uint8 * p_stream,size_t p_base,size_t p_width) {
        size_t ret = 0;
        size_t offset = p_base;
        for(size_t bit=0;bit<p_width;bit++) {
            ret <<= 1;
            ret |= extract_bit(p_stream,offset++);
        }
        return ret;
    }

class bitreader
{
public:
    inline bitreader(const t_uint8 * p_ptr,t_size p_base)
        : m_ptr(p_ptr), m_bitptr(p_base)
    {
    }

    inline void skip(t_size p_bits)
    {
        m_bitptr += p_bits;
    }

    template<typename t_ret>
    t_ret read_t(t_size p_bits) {
        t_ret ret = 0;
        for(t_size bit=0;bit<p_bits;bit++)
        {
            ret <<= 1;
            ret |= (m_ptr[m_bitptr>>3] >> (7-(m_bitptr&7)))&1;
            m_bitptr++;
        }
        return ret;
    }

    t_size read(t_size p_bits) {return read_t<t_size>(p_bits);}

    inline t_size get_bitptr() const {return m_bitptr;}

    inline bool read_bit() {
        bool state = ( (m_ptr[m_bitptr>>3] >> (7-(m_bitptr&7)))&1 ) != 0;
        m_bitptr++;
        return state;
    }

private:

    const t_uint8 * m_ptr;
    t_size m_bitptr;
};

class bitreader_fromfile
{
public:
    inline bitreader_fromfile(service_ptr_t<file> const& p_file) : m_file(p_file), m_buffer_ptr(0) {}
    
    t_size read(t_size p_bits,abort_callback & p_abort) {
        t_size ret = 0;
        for(t_size bit=0;bit<p_bits;bit++) {
            if (m_buffer_ptr == 0)
                m_file->read_object(&m_buffer,1,p_abort);

            ret <<= 1;
            ret |= (m_buffer >> (7-m_buffer_ptr))&1;
            m_buffer_ptr = (m_buffer_ptr+1) & 7;
        }
        return ret;
    }

    void skip(t_size p_bits,abort_callback & p_abort) {
        for(t_size bit=0;bit<p_bits;bit++) {
            if (m_buffer_ptr == 0) m_file->read_object(&m_buffer,1,p_abort);
            m_buffer_ptr = (m_buffer_ptr+1) & 7;
        }
    }

    inline void byte_align() {m_buffer_ptr = 0;}

private:
    service_ptr_t<file> m_file;
    t_size m_buffer_ptr;
    t_uint8 m_buffer;
};

class bitreader_limited
{
public:
    inline bitreader_limited(const t_uint8 * p_ptr,t_size p_base,t_size p_remaining) : m_reader(p_ptr,p_base), m_remaining(p_remaining) {}

    inline t_size get_bitptr() const {return m_reader.get_bitptr();}

    inline t_size get_remaining() const {return m_remaining;}

    inline void skip(t_size p_bits) {
        if (p_bits > m_remaining) throw exception_io_data_truncation();
        m_remaining -= p_bits;
        m_reader.skip(p_bits);
    }

    t_size read(t_size p_bits)
    {
        if (p_bits > m_remaining) throw exception_io_data_truncation();
        m_remaining -= p_bits;
        return m_reader.read(p_bits);
    }

private:
    bitreader m_reader;
    t_size m_remaining;
};

inline static t_size extract_bits(const t_uint8 * p_buffer,t_size p_base,t_size p_count) {
    return bitreader(p_buffer,p_base).read(p_count);
}

}